Alexander, M. JoanMountain Wave Momentum Fluxes in the SouthernHemisphere from Satellite MeasurementsAlexander, M. Joan1; Grimsdell, Alison1; Teitelbaum, Hector2

1. Colorado Research Associates Division, NWRA, Boulder,CO, USA

2. LMD, Paris, France

Accurate representation of stratospheric winds in theSouthern Hemisphere in climate models depends on theparameterization of gravity wave drag. Parameterization oforographic wave drag is widely considered to be insufficientin these models, and additional drag from non-orographicwaves is very important. Previous work has shown thestratospheric circulation affects both the seasonaldevelopment of the ozone hole, and predicted changes in21st century Southern Hemisphere climate. Recentobservational evidence suggests that small islands in theSouthern Ocean may be important sources of orographicwave drag that is currently missing in existingparameterizations. Latitudinal and downstream propagationof Andean mountain waves has also been demonstrated inrecent model studies. We provide observational estimates ofmomentum flux carried by Southern Hemisphere mountainwaves as derived from Atmospheric Infrared Sounder (AIRS)observations from the Aqua satellite. The fluxes from thesesources will be shown to cover a much broader range oflongitudes and latitudes than current orographicparameterizations predict. The analysis reveals errors in theexisting parameterizations due to missing island sources anddue to the assumption that the orographic drag only affectsthe column of air directly above the topography. Our resultsprovide some quantitative guidance for future improvementsin orographic gravity wave drag parameterizations.

Alexander, SimonWintertime gravity-wave activity in the Antarcticupper stratosphere and lower mesosphere revealedby the Davis (69°S, 78°E) lidarAlexander, Simon1; Klekociuk, Andrew1; Murphy, Damian1

1. Australian Antarctic Division, Kingston, TAS, Australia

Gravity-wave activity throughout the Antarctic upperstratosphere and lower mesosphere (USLM) is investigatedusing temperature data collected with a Rayleigh lidar atDavis, Antarctica (69°S, 78°E) during the 2007 and 2008winters. We present the first results of gravity-wave activityin the Antarctic lower mesosphere obtained using lidarmeasurements. Potential energy per unit mass shows aseasonal cycle throughout the USLM with the winter peakresulting from gravity wave Doppler shifting by the strongbackground winds. Significant variability in gravity-waveactivity occurs on short time scales between observations

(between one day and one week apart). The stratopausetemperature and height vary between observation nights onscales of several kilometres and tens of Kelvin as a result ofplanetary wave activity. The stratopause is also affected bygravity-wave activity during the night, with the regularpassage of inertia-gravity waves changing the stratopausealtitude by up to ~10km over the course of 18 hours. Gravitywave dissipation above 40 km occurs during winter, whilesignificant dissipation is only noted below the stratopauseduring autumn. Temporally filtered data with ground basedperiods of 2 – 6 hours are examined in addition to the non-filtered data, with similar seasonal cycles and short-termvariability noted. We compare the seasonality of gravity-waveenergy with other high latitude sites and suggest that themain contribution to wave energy above Davis is from non-orographic sources.

Alexander, SimonThe effect of orographic waves on Antarctic PolarStratospheric Cloud (PSC) occurrence andcompositionAlexander, Simon1; Klekociuk, Andrew1; Pitts, Michael2;McDonald, Adrian3; Arevalo-Torres, Andolsa3

1. Australian Antarctic Division, Kingston, TAS, Australia2. NASA Langley Research Center, Hampton, VA, USA3. University of Canterbury, Christchurch, New Zealand

The first seasonal analysis of the relationship betweenmesoscale orographic gravity-wave activity and polarstratospheric cloud (PSC) composition occurrence aroundthe whole of Antarctica is presented, for austral winter 2007.Gravity-wave variances are derived from temperaturemeasurements made with the Constellation ObservingSystem for Meteorology, Ionosphere and Climate (COSMIC)Global Positioning System Radio Occultation (GPS-RO)satellites. Data from the Cloud-Aerosol LIdar withOrthogonal Polarization (CALIOP) instrument onboard theCloud-Aerosol Lidar and Infrared Pathfinder SatelliteObservations (CALIPSO) satellite are used to determine thePSC composition class distribution and spatial volume. Theresults show intermittent large wave activity above theAntarctic Peninsula which is co-incident with large volumesof water ice PSCs. These ice PSC volumes advectdownstream, where increases in nitric acid trihydrate (NAT)PSC volumes occur, supporting the mountain wave seedinghypothesis throughout winter. We calculate the approximateamount of PSCs attributable to these orographic gravitywaves. While we show that planetary waves are the majordeterminant of PSC presence at temperatures close to theNAT formation threshold, we also demonstrate theimportant role of mesoscale, intermittent orographicgravity-wave activity in accounting for the composition anddistribution of PSCs around Antarctica.

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ABSTRACTSlisted by name of presenter

Alexander, SimonGlobal observations of stratospheric gravity wavesmade with COSMIC GPS-RO and comparisonswith an atmospheric general circulation modelAlexander, Simon1; Tsuda, Toshitaka2; Kawatani, Yoshio3;Takahashi, Masaaki4; Sato, Kaoru5; Klekociuk, Andrew1

1. Australian Antarctic Division, Kingston, TAS, Australia2. Research Center for Sustainable Humanosphere, Kyoto

University, Uji, Japan3. Frontier Research Center for Global Change, Japan

Agency for Marine-Earth Science and Technology,Yokohama, Japan

4. Atmosphere and Ocean Research Institute, University ofTokyo, Kashiwa, Japan

5. Department of Earth and Planetary Science, University ofTokyo, Tokyo, Japan

The launch of the six Constellation Observing Systemfor Meteorology, Ionosphere and Climate (COSMIC)satellites in 2006 and resultant ~2000 daily profiles oftemperature below 40km altitude have provided a richdataset for the analysis of mesoscale gravity waves. We willdiscuss some of the highlights of our research over the lastfew years, including comparisons between observed andmodelled gravity-wave activity. Gravity wave and equatorialwave-mean flow interaction is clearly apparent in theCOSMIC results. Tropical stratospheric gravity wavesobserved with COSMIC are seen above regions of activeconvection. Kelvin waves and mixed Rossby-gravity waveswith zonal wavenumbers < 9 are observed intermittentlythroughout the equatorial upper troposphere and lowerstratosphere. A T106L60 atmospheric general circulationmodel is used to examine the same part of the gravity-wavespectrum seen by COSMIC, with good agreement in waveactivity noted between observations and model. Largegravity-wave activity occurs around and above the wintersub-tropical jet, which decreases with altitude but increasespoleward and upward as these waves are focussed into thepolar night jets. Gravity waves seen by COSMIC in the polarregions capture the very large but intermittent nature oforographic waves forced by surface topography. Thedescending nature of the austral springtime enhancedgravity-wave activity will also be discussed, along withDoppler-shifting by the strong vortex winds.

Bardeen, CharlesEffects of Subgrid Scale Temperature VariabilityCaused by Gravity Waves Upon Simulations ofPolar Mesospheric CloudsBardeen, Charles1; Jensen, Eric2; Alexander, Joan3

1. National Center for Atmospheric Research, Boulder, CO,USA

2. NASA Ames Research Center, Moffett Field, CA, USA3. Colorado Research Associates, Boulder, CO, USA

Polar mesospheric clouds (PMC) are ice clouds thatroutinely form in the polar summer mesopause region,

where extremely cold temperatures exist because of gravitywaves. Simulations of PMCs using WACCM/CARMA, athree-dimensional chemistry climate model based upon theWhole-Atmosphere Community Climate Model (WACCM)with sectional microphysics from the Community Aerosoland Radiation Model for Atmospheres (CARMA) comparewell with observations from the Solar Occultation for IceExperiment (SOFIE); however, despite using a relatively lownucleation barrier the model underestimates the ice particlenumber density. In this study, we add subgrid scaletemperature variability from unresolved gravity waves to themodel and examine its impact on nucleation rates and PMCnumber density.

Baumgarten, GerdGravity Wave Observations in the Strato- andMesosphere by Lidar at 54°N and 69°NBaumgarten, Gerd1; Fiedler, Jens1; Gerding, Michael1;Hildebrand, Jens1; Höffner, Josef1; Lübken, Franz-Josef1

1. Optical Soundings, Leibniz-Institute of AtmosphericPhysics, Kuehlungsborn, Germany

We present characteristics of gravity waves observed byRayleigh- and resonance- lidars at Kühlungsborn (54°N,15°E) and ALOMAR (69°N, 16°E). A dataset of hourlyresolved temperature measurements covering the years since1997 was analyzed. Gravity waves are usually directly visiblein the residual temperature fluctuations with a downwardphase progession. The combination of lidar systems allowsto study waves with periods of several hours and verticalwavelengths from 5 to about 50 km. We have derived thepotential energy density (GWPED) and found that itincreases with altitude throughout the strato- andmesosphere, but slower than expected for freely propagatinggravity waves. The GWPED seasonal variation depends onaltitude and latitude. The Rayleigh-lidar at ALOMAR wasrecently upgraded for measuring wind speed by directdetection of the Doppler shift between about 30 and 80 kmwith two hours time resolution. We present a climatologicalstudy on mean GW characteristics as derived fromtemperature fluctuations and case studies of simultaneousobservation of both components of the horizontal wind andtemperature.

www.iap-kborn.de

Becker, ErichNon-orographic gravity waves in general circulationmodels (INVITED)Becker, Erich1

1. Theory and Modelling, Leibniz-Institute of AtmosphericPhysics, Kuehlungsborn, Germany

This contribution focusses on the extratropical effectsof non-orographic gravity waves (GWs) in the mesosphereand discusses issues concerning the representation of GWsin general circulation models (GCMs). First, the wave drivingconcept along with Lindzen’s explanation of the summer-winter-pole circulation in the upper mesosphere is

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recapitulated. Current GW parameterizations are based onthis framework with regard to quasi-linear theory, the single-column approximation, and a stationary GW kinetic energyequation. Beside these strong assumptions, the interactionbetween GWs and turbulent diffusion is often not clear. Thisholds in particular for parameterizations that describe acontinuous GW spectrum and specify some instabilitycriterion for spectral truncation: Conservative wavepropagation is usually assumed up to a level of waveobliteration; the resolved large-scale flow, on the other hand,is subject to the turbulent diffusion estimated from waveobliteration while the unobliterated GWs continue topropagate conservatively. This inconsistency is avoided inthe framework proposed by Becker and McLandress (2009,JAS). Some results obtained with a correspondingly extendedversion of the Doppler-spread parameterization arepresented. Furthermore, the general framework for the directthermal GW effects is outlined. A high-resolution GCM withexplicit simulation of GWs is a possible measure tocircumvent the aforementioned problems and assumptions.However, a suitable turbulent diffusion still must bespecified in order to properly describe GW-mean flowinteraction. Some results obtained with a mechanistic GCMare presented where the diffusion scheme is based on acombination of Smagorinsky’s mixing length approach andthe Richardson criterion for dynamic instability (Becker,2009, JAS). Besides the expected resolution dependence ofthe relevant GW scales, the model concept describes non-orographic extratropical GWs and their effects in themesosphere in a quite satisfactory way. A sensitivityexperiment shows that the dynamical GW sources in thestorm tracks increase with a more intense energy cycle,leading to a robust cooling of the summer mesosphere inaccordance with downward control.

Buhler, OliverInternal waves in the atmosphere and oceanBuhler, Oliver1

1. Courant Institute, New York University, New York, NY,USA

Internal waves are crucial dynamical components ofboth the atmosphere and the ocean, but for very differentreasons. Consequently, research in atmospheric and oceanicgravity waves has followed different paths, and this meansthat each side can probably learn something from the other!This talk will briefly compare and contrast the role ofinternal waves in both systems, and then discuss recentresults in fundamental dynamics of internal waves to dowith interactions with a 3d mean flow and with energytransfer mechanisms between waves and vortices.

Bushell, Andrew C.Assessing the impact of gravity waves on thetropical middle atmosphere in a GeneralCirculation ModelBushell, Andrew C.1; Jackson, David R.1; Shutts, Glenn J.1;Vosper, Simon B.1; Webster, Stuart1; Wells, Helen1

1. Met Office, Exeter, United Kingdom

A recent paper (Bushell et al., 2010) investigated thesensitivity of the tropical middle atmosphere quasi-biennialoscillation (QBO) in the MetUM general circulation modelto changes in the monthly zonal mean distribution ofclimatological ozone. Results from this experiment showedthat the increase in QBO period, which was consistent withlocally enhanced upwelling in the tropical pipe, could bereversed by enhancing by 36% the contribution from theMetUM parameterized spectral non-orographic gravity wavescheme. Investigation of the contributions to zonal windacceleration at 10hPa over the equatorial belt (5°S-5°N)indicate a reduced role for resolved waves relative toparameterized waves in that particular version of theMetUM compared with alternative models, most specificallyits predecessor. As the horizontal resolution and non-orographic gravity wave parametrization of the two versionswere similar, it was concluded that the differences arosefrom the numerical formulation of the current MetUM.Damping of fast propagating signals at the resolved lengthscale can arise from the MetUM’s semi-implicit off-centringin time and from interpolation prior to the semi-Lagrangianadvection. This area was already generating interest becauseit has implications for comparison of model output withsatellite observations that are currently resolving gravitywaves at length scales bordering on those which globalGCMs potentially have the horizontal resolution to resolve(Shutts & Vosper, in press). Results from recent experimentsto explore sensitivities of the relative contributions ofresolved and parameterized waves following changes inmodel resolution (spatial or temporal) will be presented. A.C.Bushell, D.R. Jackson, N. Butchart, S.C. Hardiman, T.J.Hinton, S.M. Osprey, L.J. Gray (2010) Sensitivity of GCMtropical middle atmosphere variability and climate to ozoneand parameterized gravity wave changes. J. Geophys. Res.,115, D15101. G.J. Shutts, S.B. Vosper (in press) Stratosphericgravity waves revealed in NWP model forecasts. Quart. J. Roy.Meteorol. Soc..

Businger, StevenSimulating the Effects of Gravity Waves OverMauna KeaBusinger, Steven1; Cherubini, Tiziana1

1. Meteorology Deptartment, University of Hawaii,Honolulu, HI, USA

Mauna Kea, Hawaii, a nearly symmetric summit risingto ~4 km from sea level in the Central North Pacific Ocean,provides an ideal laboratory to study gravity wave generationand propagation. Mauna Kea is highly instrumented with a

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multitude of meteorological and custom instrumentation.We will present preliminary results from a study of therelationship between gravity waves and turbulence profilesover the summit. Jumper et al. (2007) show a relationshipbetween atmospheric turbulence and gravity waves. Thepresence of turbulence can be correlated to the crossing ofinertial gravity waves, which locally increases the wind shearleading the Richardson number to cross the 1/4 threshold,after which clear-air turbulence is triggered (Vernin et al.2007). As part of this research, gravity wave initiation,propagation, breaking, and reflection at the top of themodel atmosphere will be evaluated with reference toobserved turbulence profiles. Favorable conditions forgravity wave breaking include interactions between the jetstream and the mountain orography, and the passage of coldor warm frontal systems. During periods when the synopticweather patterns are favorable to gravity waves generationand breaking, observational data will be investigated forsignatures of gravity waves in the turbulent profiles. Highresolution modeling studies will be run over the summit ofMauna Kea for selected cases. The model’s ability to producegravity waves will be studied and validated by comparing theobserved and simulated turbulence profiles to quantify themodel performance.

http://mkwc.ifa.hawaii.edu/

Butchart, NealThe response of parameterised gravity wavemomentum fluxes in global models to secularchanges in climate and ozone and the effects onthe general circulationButchart, Neal1; Scaife, Adam1; Hardiman, Steven1

1. Met Office Hadley Centre, Exeter, United Kingdom

Apart from orographically forced waves, parameterisedgravity waves in current global models generally have fixedamplitude sources and can only respond to climate andozone changes through a change in the filtering of thevertically propagating waves. This change in the filteringcan, nonetheless, have a significant impact on theparameterised momentum fluxes reaching different levels inthe atmosphere and thereby affect the modeled generalcirculation. A notable consequence is the contribution ofparameterised orographic gravity wave drag in acceleratingthe Brewer-Dobson circulation in climate changesimulations. Here we analyze the response of parameterisedmomentum fluxes to climate and ozone changes in a rangeof CCM and GCM simulations. The feedback of thesechanges on the climate and circulation is discussed.

Chandran, AmalThe role of planetary waves and gravity waves inSSW & elevated stratopauses as generated inWACCMChandran, Amal1; Collins, Richard1; Garcia, Rolando2;Marsh, Daniel2

1. Geophysical Institute and Department of AtmosphericSciences, University of Alaska, Fairbanks, AK, USA

2. ACD, NCAR, Boulder, CO, USA

The Whole Atmosphere Community Climate Model(WACCM) spontaneously generates multiple stratosphericsudden warming (SSW) events in simulations of the periodbetween 1953-2006. These SSWs include extreme warmingevents where the polar vortex breaks down throughout thestratosphere followed by the reformation of an elevatedstratopause at a high altitude, which then gradually drops inaltitude and warms. This is similar to the 2005/2006 majorSSW in the northern hemisphere which has been extensivelydocumented and studied from observations. In this study weanalyze the general circulation and dynamics of the upperstratosphere and mesosphere during winters with bothmajor and minor warming events as well as during quietyears with no SSW. The SSW is triggered by strong planetarywave activity, which then reverses the polar jet-stream andchanges the gravity wave forcing in the middle atmosphere.We also quantify the role of gravity waves in the formationof the elevated stratopause, reformation of the polar vortex,and coupling between the stratosphere, mesosphere, andlower thermosphere. The latitudinal and longitudinalvariations in both planetary waves and gravity wave forcingand the relative contributions of each to the circulationduring these events are also studied. We present statistics onthe frequency of occurrence of SSW events and elevatedstratopause events over the 53 winters in the free runningversion of WACCM and assess the inter-annual variability inthe polar circulation.

Chen, Ying-WenExcitation Sources of Ultra-Fast Kelvin wavesSimulated by the Kyushu-GCMChen, Ying-Wen1; Miyahara, Saburo1

1. Earth and Planetary Sciences, Kyushu University,Fukuoka, Japan

It has been revealed by model studies that Ultra-Fast-Kelvin waves (UFKs) in the upper mesosphere and lowerthermosphere (MLT) can be generated by the convectiveheating in the troposphere and propagate vertically (e.g.Forbes, 2000). On the other hand, Mayr et al. (2004)indicated that UFKs can be generated in the uppermesosphere with periods between 1 and 3 days. Origins ofUFKs in the MLT region are still an interesting unsolvedproblem. In the previous version of this study (Chen andMiyahara, in preparation), we have found that UFKs in theMLT region are possibly generated in the lower atmosphere,especially in the troposphere, and propagate vertically

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penetrating into the MLT region of the T42L250 KyushuUniversity general circulation model (the Kyushu-GCM).Using a newly made dataset sampling the convective heatingin the troposphere, our preliminary investigation shows thatthere are some relationships between the convective heatingin the troposphere and UFKs activities in the MLT region, asshown in Figure 1. It shows the time series of zonal wind andgeopotential height of UKFs with zonal wavenumber s=1 inthe period band of 2.5-3.4 days at 100 km height, and thetime series of eastward moving convective heating in thetroposphere with zonal wavenumber s=1 in the same periodband. It can be seen that there are time lags about 10 daysbetween the heating in the troposphere and the waveamplitude of UFKs at 100 km height from day-10 to day-60.It takes about 10 days for UFKs traveling through 100 km,which can be estimated based on the vertical group velocityof UKFs. This result shows that UFKs in the MLT regionfrom day-10 to day-60 are likely excited by the convectiveheating in the troposphere. On the other hand, in the timespan from day-60 to day-90, no time lags are seen. This mayindicate that UFKs in this time span may be excited by otherphysical processes besides the convective heating in thetroposphere. To identify the excitation source we needfurther analysis. The detailed analysis on the relationshipbetween excitation sources and UFKs activities in the MLTregion is now going on. Results of detailed analysis will beshown in our presentation.

Figure 1: Time series of (a) zonal wind, (b) geopotential height ofUKFs, and (c) eastward moving convective heating in thetroposphere with zonal wavenumber s=1 in the period band of 2.5-3.4 days.

Choi, Hyun-JooMomentum Flux Spectrum of Convective GravityWaves: Impacts of an Updated Parameterization ina GCMChoi, Hyun-Joo1; Chun, Hye-Yeong1

1. Dept of Atmospheric Sciences, Yonsei University, Seoul,Republic of Korea

The reference-level (cloud-top) momentum fluxspectrum of convective gravity wave drag (GWDC)parameterization by Song and Chun (2005) is updated by

determining two free parameters, the moving speed of theconvective source and wave-propagation direction, usingmesoscale simulations that explicitly resolve the convectiveGWs under various storm environments. In the updatedGWDC parameterization, the moving speed of theconvective source is determined by the basic-state windaveraged below 700 hPa. For the wave-propagation direction,a directional pair of 45° (northeast and southwest) and 135°(northwest and southeast) is considered as the best choicefor computational efficiency. The ray-based GWDCparameterization by Song and Chun (2008) with theupdated cloud-top momentum flux spectrum isimplemented in the Whole Atmosphere Community ClimateModel version 1b (WACCM1b) in addition to two existingGWD parameterizations: mountain GWD (GWDM) andbackground GWD (GWDB). The impacts of the updatedparameterization in WACCM1b are investigated in terms ofzonal-mean zonal wind and temperature, wave-inducedforcing, meridional circulations, and tropical middle-atmosphere variabilities. The results are also compared withthose of the original ray-based GWDC parameterization(RayC simulation). When both of the two update factors areincluded (RayDCQ simulation), the zonal-mean zonal windin January and July are significantly improved comparedwith the RayC simulation, especially in the polar night jetregions, equatorial upper stratosphere to subtropicalsummer mesosphere, and polar summer mesosphere. Theimprovements in the polar night jet regions (equatorialupper stratosphere to subtropical summer mesosphere) aredue mainly by the GWDC and GWDB changes (GWDCchange). The improvements in the polar summermesosphere are due to the EP flux divergence and GWDBthat are changed indirectly by updating the GWDCparameterization. The temperature is also improved in theRayDCQ simulation in January and July, especially in mid-to high-latitudes and the polar night jet regions in the bothhemispheres. These are due to the changes in meridionalcirculations by additional GWDC forcing and other waveforcing terms that are modulated by the GWDC forcing.Finally, it is found that the interannual variabilities in thetropical stratosphere related to the quasi-biennialoscillations (QBO) are enhanced in the RayDCQ simulation.The enhancements are mainly by the resolve wave forcingthat is enhanced by including the updated GWDCparameterization, while contributions by GWDB arereduced.

Chun, Hye-YeongConvective Gravity Waves and TheirParameterization: Current Status and Issues(INVITED)Chun, Hye-Yeong1

1. Dept of Atmospheric Sciences, Yonsei University, Seoul,Republic of Korea

Convective gravity waves are the major non-stationarygravity waves with wide spectrum that contributesignificantly to the momentum budget in the middle

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atmosphere when they dissipated. Even for the current high-resolution general circulation models (GCMs), theconvective gravity waves and their dissipation process aremostly unresolved, and thus they should be parameterized inthe models. During the last twenty years, there have beenseveral efforts to parameterize convective gravity waves foruse in GCMs. The main efforts have been made to formulatethe cloud-top (launch-level) momentum flux spectrum inthe 3-D framework based on the linear theory of internalgravity waves forced by diabatic heating. The cloud-topmomentum flux spectrums developed have been validatedcompared with high-resolution mesoscale simulations thatexplicitly resolve convective gravity waves. Through themesoscale simulations of convective storms developed undervarious basic-state conditions, some free parametersincluded in the parameterization can be determined. In thepropagation process, commonly used columnar method thatallows only the vertical propagation within a horizontal gridof GCM has been improved to a ray-based method thatallows the three-dimensional propagation following each rayof wave launched at the cloud top. The spatiotemporalvariation of convective sources produced from the GCMgrids can be accounted in the convective GWDparameterizations developed, although with specifiedsubgrid-scale convective source structure within the GCMgrids. The impacts of the convective GWD parameterizationin GCMs have been investigated compared with globalreanalysis and satellite data-produced gravity wavetemperature variances. Due to the limited spectral domainsobservable for each satellite, only a portion of theparameterized gravity wave spectrum can be compared withsatellite observations. The magnitudes of the momentumflux spectrum at the cloud top and above are uncertain, aswell as their temporal and spatial variations. How we canconstraint those values remains to be a challenging problem,which can be important for realistic reproduction of currentclimate and climate change simulations using GCMs thatinclude either a part of or the whole middle atmosphere.

Demissie, Teferi D.Climatology of mesospheric gravity waves and theirsources above Rothera, AntarcticaEspy, Patrick J.1; Demissie, Teferi D.1; Lund, Harald1;Hibbins, Robert E.1, 2

1. Norwegian University of Science and Technology,Trondheim, Norway

2. The British Antarctic Survey, Cambridge, UnitedKingdom

A ten-year time series of hydroxyl airglow measurementsfrom 68 S have been used to infer the wintertimeclimatology of gravity-wave variance above the AntarcticPeninsula. The hydroxyl temperature and radiancefluctuations have been combined with simultaneousradiosonde and radar observations of the wind field to tracethe mesospheric gravity waves back to their source regions.This has been carried out during periods of high and lowgravity-wave activity to examine the effects of source region

and wind direction on the net flux of gravity waves reachingthe mesosphere. The climatology of the gravity-wavevariance and source regions will be presented, and theimplications of variations in gravity-wave flux for inter-hemispheric coupling will be discussed.

Dunkerton, Timothy J.Sources of Gravity Waves in HurricanesDunkerton, Timothy J.1

1. Northwest Rsch Associates Inc, Bellevue, WA, USA

The hurricane affords a unique dynamical environmentin which the time scale of vortical processes is accelerated tobecome comparable with that of buoyant processes.Consequently we expect unique interactions between theslow and fast manifolds. The circular geometry of the stormand nonlinear modifications of primary and secondarycirculation, owing to the strength of the latter, provideseveral unique mechanisms for gravity-wave excitation.Twelve such sources have been identified in the literature.Our talk focuses on four of these: fluctuations of interiorheating in the eyewall, inertially neutral or unstable outflowaloft, pulsating radial inflow and the associated corner flowin the hurricane boundary layer under the eyewall, and therole of coherent polygonal deformations of the eyewall(associated with moist convective mesovortices) inorganizing the envelope of gravity-wave activity onintermediate and short scales. The fourth mechanismillustrates the conditional nature of convective heating,implying that gravity wave packets remain coherent withtheir eyewall mesovortex source in the near field of thestorm. This aspect is demonstrated with a high-resolutionnumerical simulation of Katrina (2005). A discrete vortical-convective mode with radiating structure in the far field isalso identified in the simulation. Some comments are made,based on geostationary satellite imagery, concerning the“hyper-fast” nature of convective triggering in the proto-hurricane environment and in tropical easterly waves.

Durran, DaleThe Up-Scale Influence of Gravity Wave BreakingDurran, Dale1; Chen, Chih-Chieh2; Hakim, Greg1

1. Atmospheric Sciences, University of Washington, Seattle,WA, USA

2. National Center for Atmospheric Research, Boulder, CO,USA

The interaction of breaking mountain waves with thelarge-scale flow is examined during the passage ofdynamically consistent time-evolving synoptic-scale flowover an isolated 3D mountain. At the ridgetop, the synoptic-scale flow accelerates and then decelerates with a period of50 hours; the maximum wind arrives over the mountain at25 hours. The impact of transient mountain-wave breakingis to produce a region of flow deceleration downstream ofthe mountain, flanked by broader regions of weak flowacceleration in the zonally averaged momentum field (seeFig. 1). Cancellation between the accelerating and

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decelerating regions results in weak fluctuations in thevolume-averaged zonal momentum, suggesting that themountain-induced circulations are primarily redistributingmomentum. Potential vorticity anomalies develop in aregion of wave breaking near the mountain and induce localregions of flow acceleration and deceleration that alter thelarge-scale flow. A “perfect’’ conventional gravity-wave-dragparameterization is tested in a coarser-resolution modelwithout a mountain. This parameterization scheme onlyproduces a weak spatial response in the momentum field,and it fails to produce enough flow deceleration near the jetcore. These results suggest that the potential vorticitysources attributable to gravity-wave breaking have acontrolling affect on the synoptic-scale response thatultimately develops downstream of the mountain.

http://www.atmos.washington.edu/~durrand/pdfs/AMS/2007Chen_Hakim_Durran.pdf

Fig. 1: Large-scale horizontal wind vectors and perturbation x-component velocities (gray scale, contour interval 1 m/s). Theregion on the centerline near the jet exit is decelerated, the twopatches to the north and south are accelerated. The ridge is shownby elevation contours.

Dutta, GopaFrequency dependence of gravity wave energy andmomentum flux estimates in the lower atmosphereusing Gadanki MST radar observationsDutta, Gopa1; Kumar, M.C. Ajay2; Kumar, P. Vinay1

1. R&D Cell, Vignana Bharathi Institute of Technology,Hyderabad, India

2. Physics, Vanajari Seethaiah Memorial College of Engg.,,Hyderabad, India

It is now well established that internal gravity waves playa significant role in the momentum and energy budgets ofthe lower and middle atmosphere. The interaction betweenvertical flux of horizontal momentum carried by these waveswith the mean winds are of great importance. But therelative contribution of different frequencies of gravity wavesto the total flux has not been investigated thoroughly andstill remains controversial. In fact measurements of thefrequency dependence of flux estimates are almost non-

existent in the tropical middle atmosphere. This paperpresents results of kinetic energy and momentum fluxestimates obtained with Mesosphere StratosphereTroposphere (MST) radar data of Gadanki, India. The radarwas operated continuously on four different days (15-16 July,2004; 18-19 April, 2005; 10-11 December, 2005; 12-13February, 2006) continuously for 24 hours and more tomeasure horizontal and vertical winds with very short datagaps ranging between 1.5 to 3.5 minutes and heightresolution of 150 m. Altitude profiles of kinetic energy andmomentum flux were obtained using these data in twoperiod bands (<2 h and 2 - 8 h). Energy and momentum fluxestimates of inertia gravity wave (IGW) were obtained usingwind data between 13 and 17 July, 2004 with a data gap of 3h. Comparisons of simultaneous measurements of kineticenergy and momentum fluxes in different period bandsreveal that the shortest period (<2 h) gravity waves transportmaximum energy and momentum fluxes in the uppertroposphere and lower stratosphere over this tropicalstation. Oscillations between 60 – 100 minutes are found tobe stronger and carry most of the flux estimates whereas forperiods <1 h, the flux is more isotropic and contribute littleto the mean momentum fluxes. In the 2 – 8 h period band,prominent oscillations between 2.5 – 6 h are found to beisotropic in nature leading to lesser mean flux estimates inthe stratosphere. Simultaneous data to study IGW wasavailable only for July 2004 case which shows that the energyand momentum transported by this longest period gravitywave was minimum. Wavelet transforms showed significantvariability and localization of the flux estimates with time.The dominant gravity wave momentum fluxes were found toarise from discrete and localized wave packets in frequencyand time.

Eckermann, Stephen D.Gravity-wave Drag Parameterization in a High-Altitude Prototype Global Numerical WeatherPrediction System (INVITED)Eckermann, Stephen D.1; Sassi, Fabrizio1; Hoppel, Karl W.2;Kochenash, Andrew3; Coy, Lawrence1; McCormack, John P.1;Baker, Nancy4; Kuhl, David D.5, 2

1. Space Science Division, Naval Research Laboratory,Washington, DC, USA

2. Remote Sensing Division, Naval Research Laboratory,Washington, DC, USA

3. Computational Physics, Inc., Springfield, VA, USA4. Marine Meteorology Division, Naval Research

Laboratory, Monterey, CA, USA5. RAP Fellowship Program, National Research Council,

Washington, DC, USA

An Advanced-Level Physics High-Altitude (ALPHA)prototype of the Navy Operational Global AtmosphericPrediction System (NOGAPS) has been developed byscientists at the Naval Research Laboratory (NRL). NOGAPSis the Department of Defense global operational numericalweather prediction (NWP) system. The NOGAPS-ALPHAprototype extends the entire system – both the global

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forecast model and the data assimilation system (DAS) – to~100 km altitude. The system has been run in anonoperational production configuration to generate 6-hourly global analysis fields from 0-100 km for key periodsin 2005-2010, based on assimilating both the archived suiteof low-altitude observations assimilated operationally byNOGAPS, plus high-altitude temperature and constituentmeasurements up to 0.002 hPa from the Sounding of theAtmosphere Using Broadband Emission Radiometry(SABER) instrument and Microwave Limb Sounder (MLS)on NASA’s TIMED and Aura satellites, respectively.Extension of this system through the mesosphere and intothe lower thermosphere has required significant work on theparameterizations of both orographic and nonorographicgravity-wave drag in the forecast model, specifically: (a)tuning, to reduce analysis-forecast (A-F) and observation-forecast (O-F) biases, and (b) numerical efficiency, to makethe parameterizations viable for future operationaltransitions. We discuss a single-wave stochastic analogue of adeterministic multiwave parameterization of nonorographicgravity-wave drag that we developed and implemented. Thestochastic scheme: (a) is an order of magnitude fastercomputationally than the deterministic parent scheme; (b)produces essentially identical time-mean climate; (c)generates explicit stochastic drag intermittency that obviatesthe need for small tuned bulk intermittency factors, and (d)increases ensemble spread. We also discuss efforts to uselarge-scale subgrid-scale drag fields derived diagnosticallyfrom the observations-based DAS products to tune thegravity-wave drag parameterizations more objectively. Thesensitivity of the system to model resolution is discussed interms of the issue of resolved versus parameterized gravity-wave drag.

Eckermann, Stephen D.Momentum Fluxes of Gravity Waves Generated byVariable Froude Number Flow over Idealized andRealistic Three-Dimensional OrographyEckermann, Stephen D.1; Lindeman, John2; Broutman,Dave3; Ma, Jun3; Boybeyi, Zafer2

1. Space Science Division, Naval Research Laboratory,Washington, DC, USA

2. College of Science, George Mason University, Fairfax, VA,USA

3. Computational Physics, Inc., Springfield, VA, USA

Fully nonlinear mesoscale model simulations are used toinvestigate the momentum fluxes of gravity waves thatemerge at a “far-field” height of 6 km from steady unshearedflow over both idealized and realistic three-dimensionalorography. In the idealized experiments, we model flow overboth axisymmetric and elliptical obstacles fornondimensional mountain heights [|#293#|]m = Fr−1 in therange 0.1–5, where Fr is the surface Froude number. Fourier-and Hilbert-transform diagnostics of model output yieldlocal estimates of phase-averaged wave momentum flux,while area integrals of momentum flux quantify the amountof surface pressure drag that translates into far-field gravity

waves, referred to here as the “wave drag” component.Estimates of surface and wave drag are compared toparameterization predictions and theory. Surface dynamicstransition from linear to high-drag (wave-breaking) states atcritical inverse Froude numbers Frc

−1 predicted to within10% by transform relations. Wave drag peaks at Frc

−1 <[|#293#|]m < 2, where for the elliptical obstacle both surfaceand wave drag vacillate owing to cyclical buildup andbreakdown of waves. For the axisymmetric obstacle, thisoccurs only at [|#293#|]m = 1.2. At [|#293#|]m > 2–3vacillation abates and normalized pressure drag assumes acommon normalized form for both obstacles that variesapproximately as [|#293#|]m

−1.3. Wave drag in this rangeasymptotes to a constant absolute value that, despite itstheoretical shortcomings, is predicted to within 10%–40% byan analytical relation based on linear clipped-obstacle dragfor a Sheppard-based prediction of dividing streamlineheight. Constant wave drag at [|#293#|]m ~2–5 arisesdespite large variations with [|#293#|]m in the three-dimensional morphology of the local wave momentumfluxes. We then progress to simulations of representativetrade winds ([|#293#|]m=5) impinging upon the Big Islandof Hawaii. We find that the wave momentum fluxes aredominated by forcing from subsidiary topographic peaks,with the broader island topography controlling flowsplitting and lee vortex generation. Waves also arise at the farnorthern and southern extremities of the island byacceleration of split flow. The strength of the localmomentum fluxes proves to be sensitive to a small change inthe incident flow direction. Areally integrated fluxes (wavedrag) align closely with the incident flow direction and arean order of magnitude smaller than linear predictions andan order of magnitude larger than corresponding dividingstreamline predictions. Specific implications of these resultsfor the parameterization of subgrid-scale orographic drag inglobal climate and weather models are discussed.

Ern, ManfredGlobal Distributions of Gravity Wave MomentumFlux Measured by Satellites: Some Implications forthe Dynamics of the Strato- and Mesosphere(INVITED)Ern, Manfred1; Preusse, Peter1; Kalisch, Silvio1

1. Institute for Energy and Climate Research - Stratosphere(IEK-7), Forschungszentrum Juelich, Juelich, Germany

The satellite instruments HIRDLS and SABER bothprovide long-term high spatial resolution data sets oftemperature altitude profiles that allow gravity wave (GW)parameters like wave amplitudes, horizontal and verticalwavelengths, and, consequently, also absolute values of GWmomentum flux to be determined. HIRDLS covers the years2005-2007 and SABER the years 2002-2010 (almost a whole11-year solar cycle). We present estimates of GW momentumflux from both instruments. Seasonal, interannual, andspatial variations, as well as implications for GWparameterizations will be discussed. For the first time globaldistributions of GW momentum flux in the mesosphere are

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derived from SABER measurements. Results show that non-vertical propagation of GWs is a significant effect. Inparticular, GW momentum flux originating from convectivesources in the subtropics during the monsoon seasons is themain contribution of GW momentum flux at midlatitudesin the summer hemisphere around 70 km altitude. Thismeans that GWs generated in the subtropics likelycontribute significantly to the reversal of the summertimemesospheric jet.

Evan, StephanieWRF model studies of tropical inertia-gravity waveswith comparisons to observationsEvan, Stephanie1; Alexander, M. Joan2; Dudhia, Jimy3

1. ATOC, University of Colorado, Boulder, CO, USA2. Northwest Research Associates, Colorado Research

Associates Division, Boulder, CO, USA3. National Center for Atmospheric Research, Boulder, CO,

USA

The NCAR Weather Research Forecast (WRF) model wasinitially developed and tested for regional simulation andweather forecasting in the troposphere. Little has beenreported on WRF performance in stratospheric simulations,or in particular stratospheric gravity wave simulations. Toaddress WRF ability to resolve stratospheric gravity wavesgenerated by convection, we conducted a series of numericalexperiments in the tropics for January-February 2006. Themodel domain is configured as a tropical channel and tominimize wave reflection effects the model top is placed at1hPa with a 15km damping layer depth. The ECMWFanalyses provide the initial conditions and boundaryconditions at the north/south boundaries throughout thesimulations. Different simulations have been performed todetermine the model sensitivity to vertical resolution,cumulus schemes and initial conditions. The modelperformance for gravity wave studies has been evaluated withhigh-resolution radiosonde horizontal wind andtemperature measurements of a 2-day inertia gravity waveevent observed during the TWP-ICE experiment. The 2-daywave properties resulting from the WRF experiments havebeen compared to those retrieved from the radiosonde dataand from the ECMWF analyses. The WRF model givescomparable results for the horizontal structure and showsbetter skill than ECMWF to resolve the vertical structure ofthe wave. Additional experiments are conducted for theaustral summer 2006. General properties of other gravitywaves in the WRF model results are further compared toECMWF analyses and HIRDLS data.

Fritts, DaveSAANGRIA (Southern Andes ANtarctic GRavitywave InitiAtive): A program to study Gravity WaveCoupling from the Troposphere into theMesosphere and Lower ThermosphereFritts, Dave1; Smith, Ron2; Doyle, Jim3; Eckermann, Steve4;Taylor, Mike5

1. CoRA, NorthWest Research Associates, Boulder, CO, USA2. Department of Geology and Geophysics, Yale University,

New Haven, CT, USA3. Naval Research LAboratory, Monterey, CA, USA4. Naval Research LAboratory, Washington DC, DC, USA5. Department of Physics, Utah State University, Logan, UT,

USA

SAANGRIA is a major airborne and ground-basedmeasurement and modeling program intended to quantifygravity wave (GW) sources in the lower atmosphere, theirpropagation through the stratosphere, and theirinteractions, instability dynamics, momentum deposition,and effects in the MLT. These objectives will be addressed bycomprehensive measurements and advanced modeling.Ground-based and airborne measurements would assessmean, tidal, and GW structures from ~30 to 70S. A suite ofnumerical modeling capabilities will permit detailedcomparisons with observations, a singular vector evaluationof upstream influences and initial conditions, assessmentsof the effects of OGW instability dynamics on momentumtransport, and the impacts of these dynamics on thecirculation, structure, and variability of the MLT. Testing ofOGW drag parameterizations in global models would beenabled by comprehensive observations, well-defined OGWforcing conditions, and high-resolution models of localterrain responses. SAANGRIA would employ the NCAR/NSFGulfstream V (G-V) research aircraft with existing and newlyfunded remote-sensing instrumentation during a 10-weekfield program during austral winter 2013 from a base atPunta Arenas, Chile. The southern Andes, Drake Passage,and Antarctic Peninsula region includes a number of majorGW sources and exhibits the largest gravity wave variances inthe stratosphere observed anywhere on Earth, making this anatural laboratory for such a study. New instruments for theG-V include Rayleigh and resonance lidars and amesospheric temperature mapper that will extend G-Vmeasurement capabilities from a current ceiling of ~20 kmto ~100 km. These measurement capabilities will beaugmented by new ground-based measurements of MLTstructure and dynamics at sites from ~30 to 68 degreessouth.

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Garcia, Rolando R.Gravity wave parameterizations in high-topmodels: Successes and problems (INVITED)Garcia, Rolando R.1; de la Torre, Laura2; Marsh, Daniel1

1. NCAR, Boulder, CO, USA2. Universidade de Vigo, Ourense, Spain

Gravity waves parameterizations, based on Lindzen’ssaturation hypothesis, were first introduced intocomprehensive, two-dimensional models of the middleatmosphere over a quarter century ago, and where quicklyshown to improve fundamentally the simulation of thecirculation, temperature and chemical structure of themesosphere and lower thermosphere (MLT). Since that time,new and more refined parameterizations have been deployed,which have further improved the performance of (now three-dimensional) middle atmosphere models, although theseimprovements are arguably incremental rather thanfundamental. This talk reviews the state of gravity waveparameterizations using as an example NCAR’s WholeAtmosphere Community Climate Model (WACCM). It isshown that gravity wave effects are important for simulatingcertain middle atmospheric phenomena, including trends insummer mesospheric temperatures and in the Brewer-Dobson circulation, the behavior of separated-stratopauseevents following stratospheric sudden warnings, and thetropical quasi-biennial oscillation. Nevertheless, manydifficult to treat problem areas remain, which arise from thenecessary simplifications embodied in the typicalimplementations of gravity wave parameterizations.

Gerber, Edwin P.Probing the Interaction Between Resolved andParameterized WavesGerber, Edwin P.1

1. Center for Atmosphere Ocean Science, New YorkUniversity, New York, NY, USA

I will present a modeling framework to investigate theinteraction between parameterized gravity wave momentumtransport and the resolved atmospheric circulation. State-of-the-art gravity wave parameterizations, both orographic andnon-orographic, are set up in a global atmospheric generalcirculation model. The model integrates the dry primitiveequation dynamics with comparable resolution to that ofcomprehensive climate models, but with a simplified forcingdesigned to create a realistic circulation, with particularfocus on capturing troposphere-stratosphere interactions.The idealized forcing allows greater control over the climateand resolution than possible with comprehensive models. Toillustrate the utility of this new model framework, a simpleexperiment is designed to highlight the interaction betweenresolved and parameterized waves in driving the Brewer-Dobson Circulation. The model is configured so that thestratospheric circulation is dominated by wavenumber 2planetary waves. The wavenumber 2 component of thesubgrid-scale topography input to the orographic gravitywave scheme is then systematically varied to alter its phase

relationship with the resolved waves. Downward controlanalysis reveals substantial changes to the circulations drivenby the resolved and parameterized waves as their phaserelationship varies, but the overall overturning circulationremains remarkably robust. This suggests a compensationbetween resolved and unresolved wave drag, a large scaleconstraint that maintains a smooth circulation. I will arguethat this compensation may relate to results fromcomprehensive models, where gravity wave drag sometimesappears to seamlessly mesh with resolved wave drag toproduce a smooth Brewer-Dobson Circulation, despite therather complex wave driving structure shown by downwardcontrol analysis.

Gong, JieGravity wave signatures in AIRS radiances: CanAIRS observe wave scales shorter than its weightingfunction thickness?Gong, Jie1; Wu, Dong L.1; Eckermann, Stephen D.2

1. Aerosol and Cloud Group, Jet Propulsion Laboratory, LaCanada Flintridge, CA, USA

2. Middle Atmosphere Dynamics, Naval ResearchLaboratory, Washington,DC, DC, USA

Gravity wave (GW) variances and preferred zonalpropagation directions are investigated using AtmosphericInfrared Sounder (AIRS) radiances at pressure altitudes of 2 -100 hPa using 50 CO2 channels. From the 90 AIRS cross-track field-of-view (FOV) measurements, we are able toaccurately derive measurement noises, high-frequencyinternal GWs, and low-frequency inertial GWs. Even thoughthe vertical wavelengths of inertial GWs are shorter than thethickness of AIRS weighting functions, the non-uniformvertical distribution of wave amplitudes produce ameasurable variance that has unique FOV dependence. Sincethe AIRS scanning is perpendicular to the polar orbitingtracks, the preferred zonal component of GW propagationcan be inferred by differencing the variances derived betweenthe leftmost and the rightmost scan angles at most latitudes.Monthly mean AIRS GW variances show large enhancementsover meridionally-oriented mountain ranges and islands atwintertime high latitudes, where GWs have predominantwestward propagation. Enhanced wave activities are alsofound above tropical deep convection regions with preferredeastward phase propagation. Annual cycle dominates bothvariables for almost all latitudes, with modulation of weakquasi-biennial oscillation (QBO) in the tropical lowerstratosphere. Simulations with idealized GWs support theAIRS sensitivity to GWs with low inertia frequencies in thetropical lower stratosphere. Characterization of these lowfrequency GWs has important implications for constrainingthe GW drag parameterization schemes in generalcirculation models and for understanding formation anddistribution of tropical cirrus clouds.

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Grimsdell, Alison W.Model study of waves generated by convection withdirect validation via satelliteGrimsdell, Alison W.1; Alexander, M. J.1; May, Peter T.2;Hoffmann, Lars3

1. NorthWest Research Associates, Colorado ResearchAssociates Division, Boulder, CO, USA

2. Center for Australian Weather and Climate Research,CSIRO/Bureau of Meteorology, Melbourne, VIC,Australia

3. Forschungszentrum Juelich, ICG-1, Juelich, Germany

Atmospheric gravity waves are a common feature of themiddle atmosphere, shaping the flow in this region bytransporting energy and momentum from the troposphere.In the tropics specifically, gravity waves are believed tocontribute to the forcing of the QBO. Gravity waves aregenerated by a variety of sources and understanding thesesources and the generation mechanism of gravity waves iscrucial to modelling of the middle atmosphere circulation.Convection is a particularly important source in the tropicsdue to the deep cumulus convection as well as the lack oftopography which precludes any topographic wavegeneration. In the case of convectively generated waves thesource can vary in both time and space, generating wavesthrough a wide range of phase speeds, frequencies andvertical and horizontal scales. In this research we examine anevent on January 12, 2003, when convective waves wereclearly generated near Darwin, Australia. Between 1500 UTCand 1700 UTC a line of storms associated with a tropicaldepression produced heavy rain and flash flooding in theDarwin region. At 1640 UTC the Aqua satellite overflewDarwin and the Atmospheric Infrared Sounder (AIRS)instrument on board provided images of a clear wave patterngenerated by this convective event. We modelled the wavegeneration using a three dimensional, non-linear, non-hydrostatic, cloud resolving model. The model was forced byprofiles of latent heating which varied spatially in all threedimensions as well as temporally. The heating profiles werederived from C-band polarimetric radar measurements andwere given at each model grid location. The depth of heatingwas derived directly from the radar reflectivity, while latentheating profiles were derived from the radar column rainfallrates. Since the model was forced with observedprecipitation patterns, the generated wave field can becompared directly to observations. This approach, usingprescribed heating, gives us both an understanding of themechanism of wave generation and the means to validate themodel results with satellite data. The results show goodagreement between the modelled wave field and thatobserved by AIRS. The curvature of the wavefronts indicatesthe latent heating from the convective storm is the majorsource of forcing for the observed waves. The conversionfrom reflectivity to heating still requires improvement,which means the wave amplitudes produced by the modelare uncertain, but the horizontal and vertical wavelengths aswell as the wave pattern are very similar to those observed byAIRS. These results provide a validation of the model

method of forcing the waves with a prescribed heating field,and the model method further provides a means ofevaluating and improving the parameterizations developedfor global model studies.

Guharay, AmitavaRayleigh lidar observations of gravity wave seasonalvariability over a tropical siteGuharay, Amitava1

1. Space and Atmospheric Sciences Division, PhysicalResearch Laboratory, Ahmedabad, India

Extensive study of middle atmospheric gravity waves(GWs) has been carried out to characterize seasonalvariability of wave associated potential energy, verticalcomponent of horizontal momentum flux and mean flowacceleration with long term database (1998-2008) overGadanki (13.5N, 79.2E), India. GWs are observed totransport significant energy and momentum flux withconsiderable variability throughout the seasons. Dominantannual oscillation (AO) is observed in the energy andmomentum flux pattern in the middle atmosphere. Meanflow acceleration due to GW divergence is found to be veryhigh in the mesosphere. Power spectral density of the verticalwavenumber spectra of normalized temperature derived forthe upper stratosphere and mesosphere exhibit resemblancein the saturated region. Logarithmic slope of verticalwavenumber spectra reveals more negative value in the upperstratosphere (~ -2.83) than the mesosphere (~ -2.43) as wellas higher magnitude during solstices and lower duringequinoxes.

Lomb-Scargle periodogram of normalized power for the mesosphereand upper stratosphere energy and momentum flux over 130months (Mar-1998 to Dec-2008).

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Logarithmic slope of the vertical wavenumber spectra for all themonths of the year for the stratosphere and mesosphere.

Hamilton, Kevin P.Topographic Drag in Ultra-Fine Resolution GlobalSimulationsHamilton, Kevin P.1; Ohfuchi, Wataru2; Satoh, Masaki2, 3

1. IPRC, University of Hawaii, Honolulu, HI, USA2. Japan Agency for Marine-Earth Science and Technology,

Yokohama, Japan3. AORI, University of Tokyo, Tokyo, Japan

The drag due to the pressure gradient acrosstopographic features is computed for high resolution globalsimulations performed with the Atmospheric GCM for theEarth Simulator (AFES) and the NonhydrostaticICosahedral Atmospheric Model (NICAM). The results arecompared with those obtained when the full topographyand pressure fields are smoothed, resulting in adetermination of drag as a function of horizontal scale. Theimplications for parameterizing the surface drag inmoderate-resolution GCMs is examined, and comparisons ofthe explicit results with the predictions of currentparameterization schemes may be presented. An attempt willalso be made to use the explicit simulations to determine thecomponent of the surface drag associated with gravity wavesthat propagate away from the surface.

Haser, AntoniaDetailed Analysis of Horizontal Wave Parametersusing Radio Occultation DataHaser, Antonia1; Schmidt, Torsten1; de la Torre, Alejandro2;Fischer, Jürgen3

1. 1.1, GeoForschungsZentrum Potsdam, Potsdam,Germany

2. Facultad de Ingeniería, Universidad Austral, BuenosAires, Argentina

3. Institude for Space Sciences, Freie Universität Berlin,Berlin, Germany

Ern et al. (2004) introduced a method to derivehorizontal wave parameters along the adjacent line of twovertical temperature profiles. The horizontal wavenumber(k_h) is given by the ratio of the phase shift (Φ) and thespatail distance dx between the regarded profiles at onealtitude k_h = ΔΦ/Δx. We apply this method to GPS radiooccultation (RO) profiles from the six-satellites constellationCOSMIC/FORMOSAT-3, delivering approximately 2500temperature profiles daily. The RO technique is a limbsounding method that is sensitive to gravity waves withsmall ratios of vertical to horizontal wavelength. To extractthe real horizontal wavelength, a third measurement isneeded. In the early mission months (April to December2006) several triads of RO profiles are found, due to theclose flying arrangement of the satellites. Before we applythis method to our dataset, a theoretical analysis is made. Asensitivity study of the Ern method shows, that the resultsfor the horizontal wavenumber and therefore all follow upproducts (like wavelength or momentum flux) have a highdependency on the horizontal distances of the measuredprofiles. Therefore the phase shift must have a lower limit,which raises with increasing distance between the profiles.Another restrain is, that the regarded profiles must bewithin one pi-phase for the Ern method to deliver the realhorizontal wavelength, once the regarded profiles are furtherapart, the results for horizontal wavelength will represent anupper boundary of the wavelength. Restrictions like thedominant vertical wavelength and a phase shift and thewavenumber comparision will be discussed. Additionally acase study in the Andes mountains is presented, deliveringwavelength between 30 and 300 km for altitudes from 20 to27 km. These results are verified using the Weather andForecast model (WRF). From global analysis for August andDecember 2006, results for the horizontal wavelength ofseveral hunderd up to 2500 km are derived.

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Heise, ReneHow to obtain a large Database of Measurementson atmospheric Gravity WavesUltsch, Alfred1; Hacker, Jorg2; Heise, Rene3

1. Databionics, University of Marburg, Marburg, Germany2. Flinders Centre for Airborne Research, Flinders

University, Adelaide, SA, Australia3. Mountain Wave Project, Berlin, Germany

The accurate prediction of atmospheric gravity wavesand the associated turbulence is a challenge formeteorological forecasting. A collection of empirical flightdata is essential in order to improve the prediction quality ofmeteorological models for atmospheric gravity waves.Inflight measures using research airplanes are costly andsuch data is rare. There is, however, a low cost source ofempirical data on atmospheric gravity waves: GPS-loggerfiles of glider flights. In 2009, for example, more than 100such flights have been made in the Andes of South Americacovering more of 50.000 km, most of them in mountainwaves (MTW). This work describes the mathematical andstatistical Data Mining and Knowledge Discovery techniquesthat are necessary in order to make meteorological use ofthis data source. Results on the occurrence, location andprobabilities of MTW in the South-American Andes asextracted from such flights are presented. Furthermore anapproach to verify the identification of gravity wave patternsin GPS logger data based on Machine Learning techniques ispresented. With these results, a first approach to a wave-climatology of the Andes and the visualization of turbulenceclassification of the rotor-wave system for briefing productsin general and commercial aviation is possible. As part of theMountain Wave Project (MWP) several flights with state-of-the-art meteorological and flight-parameterinstrumentation were made over the Andes near Mendoza,Argentina. This data serves as a benchmark for the accuracyof the GPS-logger derived data.

www.mountain-wave-project.com

Hertzog, AlbertBalloon-Borne Observations of Gravity-WaveMomentum Fluxes over Antarctica andSurrounding Areas (INVITED)Hertzog, Albert1; Vincent, Robert2; Boccara, Gillian1; Vial,François1

1. Laboratoire de météorologie dynamique, Palaiseau,France

2. University of Adelaide, Adelaide, SA, Australia

Gravity waves (together with planetary-scale Rossbywaves) drive the global scale Brewer-Dobson circulation inthe middle atmosphere. In the descending branch of thiscirculation, i.e., over the winter polar and sub-polar area, airis adiabatically compressed, resulting in a middleatmosphere significantly warmer than it would have beenunder pure radiative equilibrium. The role of gravity waves iseven more important to this respect in the Southern

Hemisphere, since the activity of larger scale Rossby waves isless there than in the Northern Hemisphere. Beside theirpure dynamical effects, gravity waves also indirectly impactthe chemistry and physics of the Southern polar vortex. Forinstance, the temperature field inside the vortex will controlmany aspects of processes involved in ozone depletion (likethe occurence and composition of polar stratospheric cloudsor chemical reaction rates) in the coming years, as long asthe decline of ozone-depleting substances will not besignificant. Hence, for a number of reasons, an accurateparameterization of gravity-waves effect in (chemistry-)climate models is needed to predict the evolution of theSouthern Hemisphere stratosphere. Such an accurateparameterization critically relies on global observations ofgravity-wave momentum fluxes. While such observationshave historically been very difficult (or even impossible) tocollect, new techniques have recently emerged, which enableus to diagnose this quantity at global scale. Estimation ofgravity-waves momentum fluxes under long-durationballoons, able to fly for several months in the lowerstratosphere on constant-density surfaces, is one of thesetechniques. Among the main assets of balloon-bornemomentum-flux estimations are the ability of providingdirectional momentum fluxes and the fact that the wholegravity-wave spectrum can be observed. The presentationwill recall the methodology used to estimate gravity-wavemomentum fluxes from observations collected during long-duration balloon flights. Results based on two campaigns(Vorcore 2005 and Concordiasi 2010) performed overAntarctica will be presented. The respective role oforographic and non-orographic waves, as well as theobserved intermittency of gravity waves will be discussed.

Hills, Matthew O.Momentum fluxes and drag profiles of trappedgravity lee waves, and their impact on the largescale flowHills, Matthew O.1; Durran, Dale R.1

1. Department of Atmospheric Sciences, University ofWashington, Seattle, WA, USA

While earlier work has suggested that trapped lee wavetrains may play an important role in the global momentumbudget, they remain difficult to represent within weatherand climate models. Observations show that current modelscommonly overestimate momentum fluxes aloft, and theneglect of gravity wave drag by lee wave trains has been citedas a potential cause of this behavior. Trapped waves are notincluded in most models, with standard parameterizationsof mountain wave drag tending to be focused onmomentum transport by vertically propagating waves in asteady flow. To address these issues, 3D simulations oftrapped waves in a time-evolving barotropic flow with alocalized jet are performed to illustrate drag mechanismswithin the waves and the resultant momentum profile.Waves generated in this study are compared to earlier 2Dand steady work on trapped lee waves and to observations.Trapped waves are forced by a 2-layer stability profile. Ray-

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tracing arguments are applied to the wave train, and candescribe the evolution (and eventual decay) of the waves inrelation to the background flow. Properties of both the wavetrain and the large-scale flow are considered in order toanalyze the impacts of the trapped waves. A slowly evolvingbackground flow (33.3 hour timescale) produces trappedwaves with characteristics that differ notably from the steadycase. Waves forced prior to the time of peak flow at themountain top are able to persist, while those forced laterwhen the flow is decelerating will eventually decay –becoming untrapped by the background flow they findthemselves within. This untrapping produces momentumand drag profiles that also vary strongly in time and space.These properties are quantified, and the origins of thebehavior identified. The impact of the wave-train on thelarge-scale flow is also analyzed. Simulations have also beenproduced using a 3-layer atmosphere – with a stratosphereadded aloft, and similar behavior observed.

Hitchcock, PeterGravity Wave-Driven Descent of the StratopauseFollowing Sudden WarmingsHitchcock, Peter1; Shepherd, Theodore1

1. Physics, University of Toronto, Toronto, ON, Canada

The zonal mean winds and temperatures in the Arcticpolar vortex undergo a characteristic and robust evolutionfor up to several months following certain stratosphericsudden warmings as planetary wave propagation into thevortex is strongly suppressed. Zonal mean temperatureanomalies from satellite observations show a tripolarstructure corresponding to the initial, planetary wave-drivenwarming in the lower stratosphere, radiatively-driven coolingin the mid stratosphere, and gravity wave-driven warming inthe upper stratosphere and mesosphere. We present adynamical analysis of the gravity-wave driven features ofthese episodes as modeled by the Canadian MiddleAtmosphere Model, a chemistry-climate model. Thesuppression of planetary wave activity during these eventsallows the stratospheric flow to evolve on radiativetimescales, making the effects of gravity waves in the polarmesosphere clear. These events may also provide a usefulmeans of testing gravity wave drag parameterizations.

Horinouchi, TakeshiAnalysis of spatial structure of gravity waves usingGPS occultation data (INVITED)Horinouchi, Takeshi1

1. Hokkaido University, Sapporo, Japan

It is found that the GPS radio occultation eventsobtained over about an hour by the COSMIC/FORMOSAT-3satellites are frequently aligned horizontally in linear shapesespecially in the first year since their launch. This featuregives an opportunity to study almost instantaneous featuresof gravity waves (GWs) in vertical cross sections, where clearGW features are frequently found. It is indicated from astatistics that horizontal wavelengths of GWs in the

northern hemisphere in winter time are generally smallerthan those in the equatorial region or in the otherhemisphere. A positive skewness is found in the probabilitydistribution of GW amplitude in mid-to-high latitudes,while it is not skewed in low latitudes. Analysis of GWpropagations relative to background winds are alsoconducted. Further analysis is made to study three-dimensional atmospheric features in high latitudes using theCOSMIC/FORMOSAT-3 data. Sharp frontal features werefrequently found at the polar vortex edge duringstratospheric sudden warmings. These features should beisolated to study GWs. The analyses is also used to studyGWs.

Huang, Tai-YinGravity Wave-induced Variations in ExothermicHeating in the MLT regionHuang, Tai-Yin1

1. Penn State Lehigh Valley, Center Valley, PA, USA

Chemical heating plays a significant role in the energybudget in the MLT region. The reactants in these exothermicreactions are oftentimes modulated in the passage of wavemotion, which would lead to variations in the chemicalheating rates. We investigate gravity wave-induced variationsin the exothermic heating in the MLT region at latitude 18in the northern and southern hemispheres. A 2D OHchemistry model with wave fields from a spectral full-wavemodel is used for such investigation in which energy lost byOH nightglow emission is taken into account. Our resultsshow that the peak values of the mean wave-induced totalexothermic heating rates are substantial, ~10.5 K/day and14.5 K/day for 18 S and 18 N, respectively. The majorcontributors to heating rates are the three-bodyrecombination O+O+M and the H+O3 reaction. Thehemispheric asymmetry in the heating rates is due to thedifferent atmospheric conditions at 18 N/S since same wavefields are used in the numerical simulations.

John, Sherine R.Investigations On Gravity Wave Potential EnergySeen By Different Satellites And Ground BasedTechniquesJohn, Sherine R.1; Kumar, Karanam K.1

1. ISRO, Trivandrum, India

Gravity waves fall in a wide spectrum of frequencies.Depending on the technique, different instruments seedifferent regions of the gravity wave spectrum. Toparameterize gravity waves in the atmosphere, a completeunderstanding of the parts of the spectrum that eachtechnique can capture is essential. In this study, a uniformmethod is used to extract gravity wave induced fluctuationsin temperature after removing 0-6 zonal wave numbercontributions. Gravity wave potential energy is thencalculated using 4 satellite based instruments, SABER, alimb viewer, HIRDLS, a limb viewer with better horizontalresolution, COSMIC, using GPS radio occultation, AIRS, a

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nadir viewing satellite, and ground based instruments likeLidar over Gadanki (13.5 N, 79.2 E) and Meteor Wind Radarover Thumba (8.5 N, 77 E). Global maps of potential energyfor Stratosphere (20-40 km) are derived which showastounding similarities among the limb viewing and radiooccultation techniques. Fig 1 is the global potential energymap derived from SABER during winter which shows polarhighs. Fig 2 shows global winds from ERA-40 which showsstrong polar jets that cause enhancement of wave activity.Further, SABER potential energy maps are calculated uptothe Mesosphere-Lower Thermosphere (MLT). Withincreasing altitude, the potential energy highs shiftequatorward from poles and at the MLT region, we findhighest potential energies at the tropics in all seasons. This isdue to Doppler shifting of wave frequency and observationalfiltering effect. Wyoming Radiosonde wind data is used forhodograph analysis and this gives an estimation ofprominent wave characteristics.

Kawatani, YoshioThe quasi-biennial oscillation in a double CO2Climate (INVITED)Kawatani, Yoshio1; Hamilton, Kevin2; Watanabe, Shingo1

1. JAMSTEC, Yokohama, Japan2. International Pacific Research Center, The University of

Hawaii, Honolulu, HI, USA

The effects of anticipated 21st century global climatechange on the stratospheric quasi-biennial oscillation (QBO)has been studied using a high-resolution version of theMIROC atmospheric GCM. This version of the model isnotable for being able to simulate a fairly realistic QBO forpresent day conditions including only explicitly-resolvednonstationary waves. We ran a long control integration ofthe model with observed climatological sea-surfacetemperatures (SSTs) appropriate for the late 20th century,and then another integration with increased atmosphericCO2 concentration and SSTs incremented by the projected21st century warming in a multi-model ensemble of coupledocean-atmosphere runs that were forced by the SRES A1Bscenario of future atmospheric composition. In theexperiment for late 21st century conditions the QBO periodbecomes longer and QBO amplitude weaker than in the late20th century simulation. The downward penetration of theQBO into the lowermost stratosphere is also curtailed in thelate 21st century run. These changes are driven by asignificant (30-40 %) increase of the mean upwelling in theequatorial stratosphere, and the effect of this enhancedmean circulation overwhelms counteracting influences fromstrengthened wave fluxes in the warmer climate. Themomentum fluxes associated with waves propagatingupward into the equatorial stratosphere do strengthenoverall by ~10-15% in the warm simulation, but the increasesare almost entirely in zonal phase speed ranges which havelittle effect on the stratospheric QBO, but which would beexpected to have important influences in the mesosphereand lower thermosphere.

Kawatani, YoshioThe roles of equatorial trapped waves and internalinertia-gravity waves in driving the quasi-biennialoscillationKawatani, Yoshio1; Sato, Kaoru2; Dunkerton, Timothy J.3;Watanabe, Shingo1; Miyahara, Saburo4; Takahashi, Masaaki5

1. JAMSTEC, Yokohama, Japan2. University of Tokyo, Tokyo, Japan3. Northwest Research Associates, Redmond, WA, USA4. Kyushu University, Fukuoka, Japan5. AORI, University of Tokyo, Tokyo, Japan

The roles of equatorial trapped waves (EQWs) andinternal inertia-gravity waves in driving the quasi-biennialoscillation (QBO) are investigated using a high-resolutionatmospheric general circulation model with T213L256resolution integrated for 3 years. The model, which does notuse a gravity-wave drag parameterization, simulates a QBO.Although the simulated QBO has a shorter period than thatof the real atmosphere, its amplitudes and structure in thelower stratosphere are fairly realistic. In the eastward windshear of the QBO, eastward EQWs including Kelvin wavescontribute up to ~25–50% to the driving of the QBO. On theother hand, westward EQWs contribute up to ~10% todriving the QBO during the weak westward wind phase butmake almost zero contribution during the relatively strongwestward wind phase. Extratropical Rossby wavespropagating into the equatorial region contribute ~10–25%,whereas internal inertia-gravity waves with zonal wavelength≤~1000 km are the main contributors to the westward windshear phase of the simulated QBO. In both the eastward andwestward wind shear phases of the QBO, nearly all Eliassen–Palm flux (EP-flux) divergence due to internal inertia-gravitywaves results from the divergence of the vertical componentof the flux. On the other hand, EP-flux divergence due toequatorial trapped waves (EQWs) results from both themeridional and vertical components of the flux in regions ofstrong vertical wind shear. Longitudinal dependence of waveforcing is also investigated by three-dimensional waveactivity flux applicable to gravity waves. Near the top of theWalker circulation, strong eastward (westward) wave forcingoccurs in the Eastern (Western) Hemisphere due to internalinertia-gravity waves with small horizontal phase speed. Inthe eastward wind shear zone associated with the QBO, theeastward wave forcing due to internal inertia-gravity waves inthe Eastern Hemisphere is much larger than that in theWestern Hemisphere, whereas in the westward wind shearzone, westward wave forcing does not vary much in the zonaldirection. Zonal variation of wave forcing in the stratosphereresults from (1) zonal variation of wave sources, (2) thevertically sheared zonal winds associated with the Walkercirculation, and (3) the phase of the QBO. This presentationreviews our recently published papers (Kawatani et al.2010a,b, J. Atmos. Sci).

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Keller, MartinRepresenting the Needed Gravity Wave Forcing inClimate Models to Drive the QBO. A Relaxation ofthe Equipartitioned Launch EPFlux with VaryingLaunch HeightsKeller, Martin1; Pulido, Manuel2; Shepherd, Theodore1

1. Deparment of Physics, University of Toronto, Toronto,ON, Canada

2. Dep. of Physics, Universidad Nacional del Nordeste,Corrientes, Argentina

GCM studies show that at low spatial resolution,parametrized GWD is an integral component of the forcingof a resolved QBO. The parameters for the GWDparametrization are often obtained via arbitrary tuning oreducated guesswork, resulting in often unsatisfactoryrepresentations of the QBO and the SAO at the stratopause.To shed light on the parameters required to acuratelyrepresent the required wave drag in the tropical stratosphere,we present the results of a number of estimationexperiments. In particular, we present estimated optimalparameters and the resulting drag profiles for Scinocca’snon-orographic GWD using a genetic algorithm. To improvethe parametrized wave drag profile, we relaxed a number ofassumptions in the parametrization. In particular, wepresent results for cases in which the assumption of anequipartitioned launch EP-flux has been dropped, andfurther discuss the dependence of these results on thelaunch height. Furthermore, we present the results ofstratospheric model simulations in order to evaluate theGWD’s ability to reproduce the QBO charasterics in asatisfactory fashion.

Kim, Ji-EunSpace-Time Variability in Precipitation at ScalesRelevant to Gravity Waves from Observations andModel ResultsKim, Ji-Eun1, 2; Alexander, M. Joan2

1. Atmospheric and Oceanic Sciences, University ofColorado, Boulder, CO, USA

2. Colorado Research Associates Division, NWRA, Boulder,CO, USA

Convectively coupled equatorial waves are closely linkedto variability in tropical precipitation. At higher frequenciesrelevant to inertia-gravity waves (IGW) the variability intropical precipitation can also describe the sources forvertically propagating waves. To evaluate the convectiveprecipitation variability at high frequency scales in a generalcirculation model and reanalyses, rainfall data from theMiddle Atmosphere configuration of the European CentreHamburg Model (MAECHAM5), the ECMWF reanalysis(ERA-interim), and NCEP/NCAR reanalysis are used inspace-time spectral analysis and the results compared withthe satellite observations from the Tropical RainfallMeasuring Mission (TRMM). At high frequenciescorresponding to IGW, the spectra display prominent lobes

following preferred propagation speeds, but the modelspeeds disagree with the ones obtained from TRMM. Whilewestward IGW modes are stronger than eastward IGWmodes in the TRMM spectrum, the model shows moresymmetric propagation of IGW. Moreover, the phase speedsof pronounced IGW modes in the model are faster than theones in TRMM, implying that the equivalent depths in themodel are scaled to deeper than the observed values. Spectraof reanalysis data generally agree with the TRMM results atlow frequencies since they are based on observations.However, spectra have significant problems at higherfrequencies, at periods of 1-day and shorter. They tend tohighly overestimate harmonics of the diurnal cycle, and soIGW modes do not stand out clearly against the background.These problems with the diurnal cycle are likely related tothe parameterized convection in the model and reanalyses.Our findings would give useful insights for theparameterization of transient waves in current climatemodels.

Kim, So-YoungInfluence of gravity waves generated by typhoon onthe typhoon developmentKim, So-Young1; Chun, Hye-Yeong1

1. Atmospheric Sciences, Yonsei University, Seoul, Republicof Korea

Gravity waves generated by typhoons have beenexamined observationally and numerically. Previous studiesof typhoon-generated gravity waves (TGWs) have focused ontheir characteristics and influence on the background flow,in particular in the stratosphere. However, to date there havebeen no studies of the feedback from TGWs to the typhoon.Numerical-modeling studies have shown significantmomentum deposition in the upper troposphere and lowerstratosphere by TGWs, and this momentum deposition canmodify the background flow. Thus, TGWs are expected toaffect their source given that the environmental flow arounda typhoon is a major factor determining the typhoon’sevolutionary processes, along with a typhoon’s internaldynamics and energy from the ocean. This study examinesthe impact of TGWs on typhoon development. We simulateTyphoon Saomai, which formed in the western Pacific inAugust 2006, and examine the background-flow changesinduced by TGWs at z = 12-17 km by calculating themomentum flux of TGWs. Then, we investigate theirpossible influences on typhoon development by consideringthe environment conditions, including the vertical windshear and divergence filed. Numerical simulations areperformed using Weather Research and Forecasting (WRF-ARW) model in three domains with horizontal grid spacingsof 27 km, 9 km, and 3 km. Three domains are nested with atwo-way interaction, and the innermost domain with a gridspacing of 3 km is designed to move following the typhooncenter. The momentum flux of TGWs and its verticaldivergence/convergence are larger in the developing stagethan in the mature and decaying stages of the typhoon. Inthe developing and mature stages of the typhoon, TGWs are

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found to act to decrease the vertical wind shear, which is oneof the inhibiting factors in a typhoon’s intensification. Onthe other hand, TGWs act to increase the vertical wind shearin the decaying stage of the typhoon. This means that TGWscan contribute to favorable vertical wind shear conditionsfor the typhoon’s developing and mature stages. Oncetyphoon intensity begins to decrease, however, TGWs canhelp a typhoon decay. Horizontal divergence also variesdepending on the typhoon’s evolution. Upper-leveldivergence, which is positively correlated with the typhoonintensity, is found to be related significantly to the activity ofTGWs.

Kim, Young-HaEffects of the Convective Gravity-Wave DragParameterization in the Global Forecast System ofthe Met Office Unified Model in KoreaKim, Young-Ha1; Chun, Hye-Yeong1; Kim, Dong-Joon2

1. Dept. of Atmospheric Sciences, Yonsei University, Seoul,Republic of Korea

2. Korea Meteorological Administration, Seoul, Republic ofKorea

The spectral convective gravity-wave drag (CGWD)parameterization by Song and Chun (2005) is implementedto the operational version of UK Met Office Unified Model(UM) 6.6 in Korea to investigate the effects of CGWD in themedium-range global forecast system. We performed one-month experiments of the five-day forecasts at every 00/12UTC for the January 2010 and July 2009 initialized from 6-hr4DVAR data assimilation cycle with (GWDC experiment)and without (CTL experiment) the CGWD parameterization.The parameterization represents well the spatial andtemporal variability of the cloud-top gravity-wavemomentum flux: the maximum eastward momentum fluxoccurs in the tropical region, whereas the maximumwestward flux exists on the oceans in midlatitudes of thewinter hemisphere along the storm tracks. CGWDmodulates the equatorial zonal winds with wave-like verticalstructures and decelerates winds in mid- to high-latitudes ofthe winter hemisphere in the stratosphere. By CGWD, themean zonal and meridional circulations are modified, inaddition to the changes in other forcing terms (e.g. theresolved-wave forcing, Coriolis force, non-orographic gravity-wave forcing). The tropical stratospheric wind biases forboth months in the CTL experiment are reduced by 10 − 20%in the GWDC experiment: the excessive easterly in the mid-stratosphere is weakened, and the positive and negativebiases of the near-zero winds in the upper and lowerstratosphere, respectively, are reduced. The cold pole biasand westerly biases in midlatitudes of the winterstratosphere are also alleviated by ∼10%. In the troposphere,the tropical circulation is significantly modified, and thismodulates rainfalls so that the precipitation errors arereduced, particularly in the January 2010. Based on the skillscores of 5-day forecasts, mid-tropospheric geopotentialheights and lower tropospheric temperatures in the tropicsare forecasted better in the GWDC experiments. The root-

mean-square errors (RMSE) of the 500-hPa geopotentialheights are reduced by 5 − 10% for the both months, andthose of the 850-hPa temperatures by ∼5% for the July 2009.

Krismer, ThomasLarge scale equatorial waves and the quasi-biennialoscillation in ECHAMKrismer, Thomas1; Giorgetta, Marco1

1. Max Planck Institute for Meteorology, Hamburg,Germany

The quasi-biennial oscillation (QBO) in the tropicalstratosphere is driven by wave mean flow interactionsinvolving different types of waves occurring in the equatorialstratosphere. This study aims at a quantification of thecontribution of large scale waves, defined by spectral filters,to the QBO simulated in ECHAM5 and ECHAM6 atresolutions ranging from T42 (2.8°) L90 to T127 (0.94°)L95. These simulations show QBOs with realistic periodsand amplitudes, resulting from resolved and parameterizedwave mean flow interaction. The wave analysis performed onthese simulations gives special emphasis to representation,source regions and propagation properties of the resolvedequatorial trapped waves and large scale inertia gravitywaves. Fields of outgoing long wave radiation, temperatureand divergence clearly show these waves as predicted bylinear theory, suggesting that the modeled troposphericweather generates a realistic wave spectrum. Thecontribution of the different wave types to the momentumbudget of the QBO is illustrated by the momentum fluxdivergence of the filtered wind and temperature fields andcompared to ERA40 data.

Kumar, M.C. AjayCharecteristics of inertia gravity waves in the loweratmosphere over Hyderabad (17.4 °N, 78.5 °E)Kumar, M.C. Ajay2; Satyakumar, M.3; Reddy, Y. K.3; Dutta,Gopa1

1. R&D Cell, Vignana Bharathi Institute of Technology,Hyderabad, India

2. Physics, Vanjari Seethaiah Memorial College of Engg.,Hyderabad, India

3. Indian Meteorological Department, Hyderabad, India

Gravity waves with short vertical scales are observed tohave pronounced activity in the tropics. We report here thecharacteristics of short vertical wavelength inertia gravitywaves using the high resolution (~ 50 m) GPS radiosondemeasurements of horizontal winds and temperature madeby India Meteorological Department (IMD) Hyderabad. Theballoon flights are carried out twice a day at 0000 GMT and12) GMT with on-board GPS receiver and radiosondemanufactured by MODEM company of France. Theaccuracies of wind and temperature are 0.15 m/s and ±5°Crespectively. The data collected between 15 May and 24September, 2009 have been used for the present study.Hodograph analysis have been carried out to delineatevertical and horizontal propagation characteristics. Most of

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the hodographs in the middle and upper troposphere showanticlockwise rotation signifying downward energypropagation. This indicates that the jet velocity observedduring this period might be a strong source of IGW. Thestratospheric analysis show predominantly upwardpropagation of energy. The direction of propagation of IGWwere further confirmed by analyzing hodographs of u’ - t’. Asystematic change of the direction of IGW from south-westto south-east could be observed between May to September.Similar observations were made for both tropospheric andstratospheric regions. A typical vertical wavelength was 2.5 –3.5 km and the horizontal wavelength varied between 250 to1000 km. Vertical profiles of wind and temperaturefluctuations were subjected to spectral analysis to formvertical wave number spectra and were compared withsaturated model spectrum. Spectral indices of the windspectra were found to be -2.2 and -2.5 for tropospheric andstratospheric regions respectively. The correspondingspectral slopes for temperature spectra are -3.2 and -3.5.

Kumar, P. VinayFirst observation of quasi-two-day wave in thelower atmosphere over Hyderabad (17.4 N, 78.5 E)Kumar, P. Vinay1; Dutta, Gopa1; Mohammad, Salauddin1

1. R&D Cell, Vignana Bharathi Institute of Technology,Hyderabad, India

The quasi-2-day wave is a global oscillation frequentlyobserved in the middle and upper atmosphere duringsolstices. The 2 - day wave has been associated with Rossby-gravity mode of zonal wave number 3 and also baroclinicinstability of summer easterlies. In this paper, we haveinvestigated the characteristics of this wave in the loweratmosphere (1-31 km) of a tropical station Hyderabad (17.4N, 78.5 E). India Meteorological Department (IMD)conducts regular GPS radiosonde flights twice a day fromHyderabad. The high resolution (1 sec) data of wind andtemperature between 15 May and 24 September, 2009 in thealtitude range of 1 – 25 km have been used for the presentstudy. Two - day waves of appreciable amplitude could beobserved in both zonal and meridional winds and also intemperature data. FFT analyses identified the waves in twoperiod bands (44-52 h and 56-60 h) with longer periodsbecoming more prominent in the months of August andSeptember. Maximum amplitudes of ~ 4-5 m/s are found inthe upper troposphere and lower stratosphere withdownward phase propagation. The thermal amplitudemaximum is ~ 2.2 K in the same region. Wavelet analysisshows a continuous systematic bursts of QTDW during thesummer solstice and a clear modulation of 2 - day waveamplitude by a planetary wave of 7-10 days period. Thepropagating QTDW appears to interact with backgroundwind and the zonal wind is found to change systematicallybefore, during and after the wave bursts.

Langford, Andrew O.Lidar Observations of Convection Waves aboveHouston during TexAQS2006Langford, Andrew O.1; Senff, Christoph J.2, 1; Alvarez II, RaulJ.1; Banta, Robert M.1; Hardesty, R. M.1

1. CSD, NOAA ESRL, Boulder, CO, USA2. CIRES, U. of Colorado, Boulder, CO, USA

Convection waves are formed when thermals in theconvective boundary layer impinge on the overlaying stablelayer in the presence of strong wind shear. These small-scalewaves can extend throughout the troposphere and into thestratosphere, and also initiate and organize moistconvection. Convection waves can potentially form anywherethere is strong surface heating and thus may be animportant source of wave activity in many areas. Althoughconvection waves are well known to glider pilots and havebeen observed by aircraft over the midwestern U.S., and oversouthern Germany (where they have also been detected by aground-based radar profiler), there are relatively fewpublished observations. Here we describe airborne lidarobservations of convection waves made during the TexAQS2006 campaign in Houston, Texas. Wave activity was seenfollowing the passage of a cold front, with ozone and aerosollidar profiles showing clear signatures of wave activity nearthe top of the convective boundary layer (≈1.7 km msl). Thewaves were relatively long-lived and propagated into themean wind with a horizontal wavelength of ≈5 km. Theywere trapped by a second stable layer ≈1.5 km above the topof the convective boundary layer, and wave activity was alsoseen in temperature measurements near the bottom of thislayer. Although the lidar measurements were made underclear sky conditions, the waves appear to be associated withcloud streets that formed ≈30 km to the west. These resultswill be compared to previous observations and modellingstudies.

Lelong, PascaleMixing efficiency of breaking inertia-gravity wavesLelong, Pascale1; Bouruet-Aubertot, Pascale2

1. Northwest Research Associates, Seattle, WA, USA2. LOCEAN-IPSL, Univ. of Paris VI, Paris, France

The energy budgets of numerically simulatedmonochromatic breaking inertia-gravity waves are analyzedfor a broad range of wave frequencies and amplitudes.Whereas low-frequency waves are most unstable to shearinstability, higher-frequency waves break preferentially viaconvective instability and intermediate-frequency wavesexhibit a hybrid shear-convective instability. We find that athigh frequencies, the bulk of the mixing occurs in the pre-turbulent phase of wave breaking. This corresponds to theregime where dissipation is weak relative to the diapycnalflux. At low frequencies and high amplitudes, the peak inmixing is in phase with the fully turbulent regime. Forconvectively stable low-frequency waves, significant mixingoccurs once again in the pre-turbulent regime. The relativeduration (in wave periods) of pre-turbulent to turbulent

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phases appears to govern whether a wave will mix efficientlyor not prior to turbulent breakdown. These results are ingeneral agreement with those of Inoue and Smyth (JPO,2009) who considered the mixing associated with instabilityof shear flows subjected to time-periodic forcing. We alsofind that mixing efficiencies are highest for high-frequencywaves. The dependence on Prandtl number is also examined,with higher Prandtl numbers leading to weaker mixing rates.

Li, YanpingObservation and theory of the diurnal continentalthermal tideLi, Yanping1; Smith, Ronald B.2

1. IPRC, University of Hawaii, Honolulu, HI, USA2. Dept of Geology and Geophysics, Yale University, New

Haven, CT, USA

Harmonic analysis of summer ASOS data over NorthAmerica shows sun-following diurnal temperature andpressure oscillations with amplitudes increasing in thewestern USA, i.e. 5 to 8 degC and 60 to 120 hPa respectively,due to larger sensible heating in the dryer western terrains.The phases of temperature and pressure (i.e. 220deg and110deg) are constant with longitude after an interferingeastward propagating wave is subtracted. Tidal amplitudesand phases shift significantly with season. A linearBoussinesq model can capture these observed tidalproperties with properly selected parameters. A dampingparameter alpha=5~9*10-5 1/s, comparable to the inertiaand Coriolis parameters, is needed to explain thetemperature phase lag relative to local solar noon (40deg to50deg). The phase lag between surface pressure minimumand temperature maximum (45deg to 70deg) requires a 3 to5 hour time delay between surface and elevated heating. Theratio of pressure and temperature amplitude requires aheating depth varying between 550 to 1250 meters; winter tosummer. Both the heating delay and depth are consistentwith a vertical heat diffusivity of about 10 m2*s-1 in winter,but K-theory give inconsistent summer values. The tideamplitude requires diurnal heating amplitudes in the rangeof 100 to 200 W/m2. When the tuned model is applied to anidealized but inhomogeneous continent, the travelingdiurnal heating generates gentle tides over the large uniforminterior regions but causes vigorous sea breezes andmountain-plain circulations in regions of heating gradient.These gradient regions have significant vertical motions andare moderately sensitive to the critical latitude and the meanwind speed. Surprisingly, these local circulations do not alterthe phases of the temperature and pressure oscillations, inagreement with observations.

http://journals.ametsoc.org/doi/abs/10.1175/2010JAS3384.1

Li, ZhenhuaGravity Wave Characteristics in the Mesopauseover Andes MountainsLi, Zhenhua1; Liu, Alan2; Lu, Xian1; Steve, Franke3; Swenson,Gary R.3

1. Atmospheric Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA

2. Electrical and Computer Engineering, University ofIllinois at Urbana-Champaign, Urbana, IL, USA

3. Physical Sciences, Embry-Riddle Aeronautical University,Daytona Beach, FL, USA

Gravity wave parameters in the mesopause region wereanalyzed from newly acquired all sky imager data taken atthe Andes Lidar Observatory (ALO) at Cerro Pachón, Chile(30 S, 71W) with collocated meteor radar providingbackground wind (Sep 2009 to present). The wavepropagation directions, phase speed, and horizontal andvertical wavelengths were derived. The results from thismountainous site were compared with results using the datafrom Maui (21N, 157 W, 2002-2007), an oceanic site. Thecomparisons between the results at these two sites showcommon features such as dominant wave phase speed, andhorizontal wavelength. However, the directionality of wavepropagation shows strong seasonal and geographicaldifferences. Gravity wave momentum flux shows a strongseasonal and diurnal variation that is anti-correlated withthe background mean wind. The implications of the rolesplayed by the momentum flux deposition on the mean floware explored on both seasonal and diurnal time scale. Theseasonal/diurnal variations of occurrence frequencies ofpropagating and evanescent waves are also examined. Severalunusual wave events, including bore-like features and largeamplitude waves will be presented.

Liu, Alan Z.Wave Induced Transport of AtmosphericConstituents and Its Effect on the Mesospheric NaLayerLiu, Alan Z.1, 2; Gardner, Chester S.2

1. Embry-Riddle Aeronautical University, Daytona Beach,FL, USA

2. University of Illinois, Urbana, IL, USA

Extensive observations of winds, temperatures and Nadensities between 80 and 105 km at the Starfire OpticalRange, NM are used to characterize the seasonal variationsof the vertical flux of atomic Na and its impact on the Nalayer. The largely downward Na flux and its convergenceenhances the transport of Na from meteoric sources above90 km to chemical sinks below 85 km, altering the height,width and abundance of the Na layer. From theoreticalconsiderations, it is shown that the effective vertical velocityassociated with dynamical transport by dissipating waves isthe same for all species and is about 3 times faster than theeffective heat transport velocity. Dynamical transport isgenerally downward with velocities as high as −5 cm/s below

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90 km in mid-winter when and where gravity wave activityand dissipation are strongest. Chemically induced transportof atomic Na by both dissipating and non-dissipating wavesis also significant so that the total effective transportvelocity for Na below 90 km approaches −8 cm/s in mid-winter. The observations show that at the solstices,dynamical and chemical transport play far more importantroles than turbulent mixing in transporting Na downwardwhile at the equinoxes the impacts of all three wave inducedtransport mechanisms are comparable. These results haveimportant implications for chemical modeling of themesopause region.

Llamedo Soria, PabloLong-term global GW activity in lower and middleatmosphere from CHAMP, GRACE and COSMICradio occultation data between 2001 and 2010Llamedo Soria, Pablo1; de la Torre, Alejandro1; Alexander,Pedro2; Hierro, Rodrigo1; Schmidt, Torsten3; Wickert, Jens3;Haser, Antonia3

1. Universidad Austral, Buenos Aires, Argentina2. Universidad de Buenos Aires, Buenos Aires, Argentina3. Geoforschungs Zentrum, Potsdam, Germany

We discuss the long-term global tropospheric-stratospheric gravity wave (GW) activity expressed by thespecific potential energy derived from GPS radio occultationdata, as retrieved by CHAMP, GRACE and COSMIC LowEarth Orbit (LEO) satellites between 2001 and 2010.Systematic annual and interannual features as a function oflongitude, latitude and time are shown, extending and/ormodifying results and features pointed out in previousclimatologies. Possible over/under estimations due to thedata processing are also remarked. The GW analysis is basedon the correct extraction of the perturbation component ofthe individual measured temperature profiles by applyingdifferent filtering techniques. We test a new filteringprocedure that considerably reduces the usually observedwave activity enhancement at the tropopause. After applyinga bandpass filter, the perturbation component is detrendedagain to force a zero mean. For reference, we create knownsynthetic perturbation components added to backgroundtemperature profiles to compare the ability of the differentfiltering methods. This filtering procedure considerablyreduces a systematic over estimation of the wave activityobserved in previous climatologies, mainly at tropopauseregions.

Love, Peter T.Observational Constraints on the Spectrum ofGravity Waves Generated by Tropical ConvectionLove, Peter T.1

1. Institute for Terrestrial and Planetary Atmospheres,Stony Brook University, Stony Brook, NY, USA

Ray-tracing techniques are employed to simulate gravitywave propagation through the equatorial middleatmosphere in the central Pacific. Multiple time-dependent

simulations are carried out using a variety of multi-yeartime-series observations to specify monthly meanbackground atmospheres with tidal perturbations. Initialgravity wave parameters for simulations are specified from arange of deep convection gravity wave source models.Simulation results are compared to radar observations ofmiddle atmospheric gravity wave activity to infer the mostaccurate source model and its spectral characteristics. Theinferred source spectrum characteristics are analyzed inrelation to meteorological conditions during the period ofeach simulation to assess the consistency with theoreticalmodels of gravity wave excitation by deep convection.Results infer a highly anisotropic source spectrum with peakmomentum flux preferentially aligned with troposphericwinds.

Lu, XianMomentum budget analysis on the seasonalvariation of the diurnal tide by using the WholeAtmosphere Community Climate Model(WACCM4) and its comparison with the meteorradar and satellite observationsLu, Xian1; Liu, Alan Z.2; Liu, Han-Li3; Li, Zhenhua1;Swenson, Gary R.4; Wu, Qian3; Yue, Jia3; Franke, Steven J.4

1. Atmospheric Sciences, University of Illinois, Urbana, IL,USA

2. Physical Sciences, Embry Riddle Aeronautical University,Daytona Beach, FL, USA

3. High Altitude Observatory, National Center forAtmospheric Research, Boulder, CO, USA

4. Electrical and Computer Engineering, University ofIllinois, Urbana, IL, USA

By using the meteor radar and TIDI satellite windobservations, it is found that the seasonal variation of thediurnal tide is dominated by the semiannual oscillation(SAO) at low latitudes, which reaches the maximumamplitude at equinox and minimum at solstice. The phase ofthe diurnal tide is also changing seasonally. The tidalheating by the absorption of infrared solar radiation in thetroposphere is thought to be playing an important role tocause the SAO as it has more symmetric and efficientprojection on the gravest diurnal tide component W1 atequinox than at solstice. The linear advection, nonlinearadvection and gravity waves may also contribute to theseasonal variation of the diurnal tide. The comparison withobservation shows that the seasonal variation of the diurnaltide is well reproduced by the Whole AtmosphereCommunity Climate Model 4 (WACCM4) while themagnitude is smaller than observation. To study themechanisms contributing to the seasonal variation, we carryout a momentum budget analysis on the diurnal tide andevaluate the effects from Coriolis and geopotential gradientforces, linear advection, nonlinear advection and gravitywaves. This analysis identifies the most dominant termscontributing to the seasonal variation of the diurnal tide.The momentum budget is modulated by the meantemperature and winds, which are sensitive to the GW

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parameterization. This sensitivity is investigated using theGW parameterization scheme in the WACCM4, which relatesGW generation to orography, convective and frontalactivities individually. The sensitivity of GW effects on thediurnal tide is also analyzed for this scheme.

McDonald, AdrianMeasuring gravity wave intermittency andpropagation directions from satellite observationsMcDonald, Adrian1; Chu, Xinzhao2; Kratt, Matrina1

1. Department of Physics and Astronomy, University ofCanterbury, Christchurch, New Zealand

2. CIRES, University of Colorado, Boulder, CO, USA

It is well known that satellite observations of the Earth’satmosphere have the potential to provide global-scaleconstraints for gravity wave parameterizations. Initialsatellite-based analyses focused on gravity waves examinedthe climatological features of wave activity. More recentlydeveloped processing schemes which derive horizontal andvertical information using paired satellite observations haveimproved the amount of gravity wave information that canbe obtained (e.g. momentum fluxes). But, the uncertaintieson these measurements can not be quantified and are largebased on theory. The problems associated with the different‘observational filters’ of different observing systems providesanother difficultly in interpreting satellite observations. Inthis study, we primarily examine the possibility of derivinginformation on the intermittency and propagation directionof gravity waves using data from the COSMIC constellation.This observing system uses the GPS radio occultationmethodology on data from six near-identical observingsatellites to produce extremely accurate and precise highresolution measurements of atmospheric temperaturebetween approximately 10 and 40 km. These characteristicsallow us to make measurements of small-scale waves.However, the configuration of the satellites’ orbits in theconstellation means that the spatial and temporaldistribution of observations is not uniform and analysisshows that ‘clusters’ of observations occur relatively often.The occasional dense sampling of a region, characterized byseveral measurements made within a 250 km radius of eachother and separated by less than one hour, offers theopportunity to explore: a. the spatial variability of measuresof gravity wave activity b. the coherence between the gravitywaves observed in profiles separated by a range of smalldistances. c. the uncertainty of satellite observations of waveactivity d. the observational filter of the Radio occultationmeasurements. e. Intermittency of gravity waves f.Propagation directions of waves This presentation exploresthese possibilities and follows-on from previous workdiscussed in Horinouci and Tsuda (2009) and McDonald etal. (2010).

Medvedev, Alexander S.Influence of Vertically Propagating Gravity Waveson the Atmosphere of MarsMedvedev, Alexander S.1; Yigit, Erdal2; Hartogh, Paul1

1. Max Planck Institute for Solar System Research,Katlenburg-Lindau, Germany

2. Atmospheric, Oceanic and Space Sciences, University ofMichigan, Ann Arbor, MI, USA

Observations and theoretical considerations point outto much stronger than on Earth generation of gravity waves(GWs) in the troposphere of Mars due to instabilities ofweather systems, volatile convection, and flow over therugged topography. Disturbances attributed to GWs haveamplitudes several times larger than on Earth in bothMartian lower and upper atmospheres. However, unlike onEarth, the significance of these vertically propagating wavesis not yet well established. General circulation models(GCMs) are apparently able to reproduce the observedcirculation patterns without parameterized GWs, at least upto 80-100 km. The submission addresses the fundamentalgap in the knowledge of the momentum budget in theMartian upper atmosphere. Using our recently developedGW parameterization suitable for thermospheres [1] and aMartian GCM, we quantify for the first time the GWmomentum deposition at thermospheric heights. It isshown [2] that GW drag plays a role similar to the one in theterrestrial lower thermosphere but somewhat higher, at 110-130 km, at altitudes where the recently observed temperaturedeviates significantly from model simulations [3].The reasonfor the difference lies in stronger than on Earth EP fluxdivergence due to resolved waves, and the pecularities of GWpropagation. 1. Yigit, E., A.D. Aylward, A.S. Medvedev,J.Geophys. Res., 113, D19106, doi:10.1029/2008JD010135,2008. 2. Medvedev, A.S., E. Yigit, P. Hartogh, Icarus, 2010, inpress. 3. Forget, F. et al. J. Geophys. Res., 114, E01004,doi10.1029/2008JE003086, 2009

Miyahara, SaburoA Three-Dimensional Wave Activity Flux Applicableto Inertio-Gravity Waves (INVITED)Miyahara, Saburo1

1. Department of Earth and Planetary Sciences, KyushuUniversity, Fukuoka, Japan

In the last decade, global distributions of activity ofgravity waves have been extensively revealed numerically andobservationally. It is shown that the activity substantiallyvaries in longitudinal direction. If the activity were almosthomogeneous in longitudinal direction, the Eliassen-Palmflux (EP flux) analysis would be useful to investigate wavepropagation in the meridional plane and zonal mean eddyforcing by the wave disturbances (e.g., Andrews and McIntyre1976; Andrews et al. 1987). The EP flux analysis, however, isnot practical to analyze longitudinally varying disturbances,because the EP flux is based on the zonal mean. To remedythis drawback, the EP flux has been extended to three-dimensional fluxes that are applicable to longitudinally

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varying quasi-geostrophic disturbances (e.g., Plumb 1985,1986; Trenberth 1986; Takaya and Nakamura 2001). In thispresentation a three-dimensional wave activity flux that isapplicable to non-hydrostatic and non-geostrophicdisturbances such as gravity waves, and a three-dimensionally extended transformed Eulerian-meanequation system are explained using a Boussinesq fluid onbeta-plane (Miyahara 2006). The three-dimensional fluxtensor is equal to the flux related to the wave-action densityrelative to time-mean flow at the WKB limit. The three-dimensional transformed Eulerian-mean equation can bederived by introducing a three-dimensional residual meancirculation and by the divergence of the flux tensor. Theresidual mean circulation gives the Eulerian-meancirculation plus Stokes drift in the three-dimensional space,and the divergence of the flux tensor gives local east-westand north-south time-mean eddy forcing on time-meanflow. The results of the Boussinesq case can be readilyapplied to hydrostatic non-geostrophic disturbances denotedby the log-pressure coordinate system on spherical geometry.Some examples of the application of the flux to non-geostrophic wave disturbances in several General CirculationModels will be shown in the presentation. ReferencesAndrews, D. G. and M. E. McIntyre, 1976: Planetary waves inhorizontal and vertical shear: the generalized Eliassen-Palmrelation and the zonal mean acceleration. J. Atmos. Sci., 33,2031-2048. Andrews, D. G., J. R. Holton, and C. B. Leovy,1987: Middle Atmosphere Dynamics, 489pp, Academic Press.Miyahara, S.: A three dimensional wave activity fluxapplicable to inertio-gravity waves. SOLA, 2, 108-111,doi:10.2151/sola.2006-028. Errata. Plumb, R. A., 1985: Onthe three-dimensional propagation of stationary waves. J.Atmos. Sci., 42, 217-229. Plumb, R. A., 1986: Three-dimensional propagation of transient quasi-geostrophiceddies and its relationship with eddy forcing on the time-mean flow. J. Atmos. Sci., 43, 1657-1678. Takaya, K. and H.Nakamura, 2001: A formulation of a phase-independentwave-activity flux for stationary and migratoryquasigeostorophic eddies on a zonally varying basic flow. J.Atmos. Sci., 58, 608-627. Trenberth, K. E., 1986: Anassessment of the impact of transient eddies on zonal flowduring a blocking episode using localized Eliassen-Palm fluxdiagonostics. J. Atmos. Sci., 43, 2070-2087.

Miyazaki, KazuyukiTransport and mixing in the extratropicaltropopause region in a high vertical resolutionGCMMiyazaki, Kazuyuki1, 2; Sato, Kaoru3; Watanabe, Shingo2;Tomikawa, Yoshihiro4; Kawatani, Yoshio2; Takahashi,Masaaki3

1. Royal Netherlands Meteorological Institute, De Bil,Netherlands

2. Japan Agency for Marine-Earth Science and Technology,Yokohama, Japan

3. University of Tokyo, Tokyo, Japan4. National Institute of Polar Research, Tokyo, Japan

A high-vertical resolution general circulation model(GCM) output has been analyzed to clarify transport andmixing processes in the extratropical tropopause region. Thehigh-resolution GCM, with a vertical resolution of about300 m above the extratropical upper troposphere, allowssimulation of fine atmospheric structures near thetropopause, such as the extratropical tropopause transitionlayer (ExTL) and the tropopause inversion layer (TIL). Thehigh-resolution GCM realistically simulates fine thermaland dynamic structures in the extratropical tropopauseregion. The high-resolution output was analyzed using azonal mean potential vorticity (PV) equation to identifydominant transport processes in the extratropicaltropopause region. In the northern hemisphere extratropicsduring winter, mean downward advection sharpens the PVgradient between the tropopause and 20 K below it, whereaslatitudinal variation in isentropic mixing sharpens thevertical PV gradient between the tropopause and 10 K aboveit. During summer, vertical mixing substantially sharpensthe vertical PV gradient at 10-25 K above the tropopause.These sharpening effects may be strongly related to theformation mechanisms of strong concentration gradients ofchemical tracers around the ExTL. Mechanisms of evolutionof the TIL are also discussed by analyzing a thermodynamicequation. Downward heat advection and radiation processesprimarily determine the seasonality of the TIL. The analysisresults suggest that the locations of the TIL and the ExTLcan be similar because of common dynamic processes andinteractions between constituent distributions and thermalstructure. The relative roles of atmospheric motions onvarious scales, from meso-wave scale to planetary scale, intransport and mixing in the extratropical tropopause regionare also investigated. A downward control calculation showsthat the E-P flux of the gravity waves diverges and induces amean equatorward flow in the extratropical tropopauseregion, which differs from the mean poleward flow inducedby the convergence of large-scale E-P fluxes. The diffusioncoefficients estimated from the eddy potential vorticity fluxin tropopause-based coordinates reveal that isentropicmotions diffuse air between 20 K below and 10 K above thetropopause from late autumn to early spring, while verticalmixing is strongly suppressed at around 10–15 K above thetropopause throughout the year. The isentropic mixing ismainly caused by planetary- and synoptic-scale motions,

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while small-scale motions with a horizontal scale of less thana few thousand kilometer largely affect the three-dimensional mixing just above the tropopause. Analysis ofthe gravity wave energy and atmospheric instability impliesthat the small-scale dynamics associated with the dissipationand saturation of gravity waves are a significant cause of thethree-dimensional mixing just above the tropopause. A rapidincrease in the static stability in the tropopause inversionlayer is considered to play an important role in controllingthe gravity wave activity around the tropopause.

Murphy, Damian J.Using Antarctic observations to improve gravity-wave parameterization in climate modelsMurphy, Damian J.1; Alexander, Simon1; Klekociuk,Andrew1; French, John1; Eckermann, Stephen2; McDonald,Adrian3; Taylor, Mike4; Vincent, Robert5; Reid, Iain5

1. Department of Sustainability, Environment, Water,Population and Communities, Australian AntarcticDivision, Kingston, TAS, Australia

2. Space Science Division, Naval Research Laboratory,Washington, DC, USA

3. Department of Physics and Astronomy, University ofCanterbury, Christchurch, New Zealand

4. Department of Physics, Utah State University, Logan, UT,USA

5. School of Chemistry and Physics, University of Adelaide,Adelaide, SA, Australia

An extensive suite of instruments capable of measuringwinds and temperatures in the lower and middle atmosphereoperates at Davis station (69S, 78E) in Antarctica, includingsome instruments which have been making observations fora decade or more. Recently, a project has begun that seeks touse the instruments available at Davis station to improveobservational constraints on the gravity-waveparameterization schemes used in numerical climate andweather prediction models, assist in driving them towardstheir next generation and so improve predictions ofatmospheric change. The breadth of character of gravitywaves, along with the complexity of numerical models,makes it necessary to focus the observations of this project.Gravity-wave parameterization schemes share two commoncharacteristics; they assume a gravity wave sourcedistribution near the model base; and they have the forceapplied to the atmosphere as their output. This project willtake a multi-instrument approach to observing these twoparts of the life cycle of gravity waves. It will then use theresultant observational constraints to identify improvementsto parameterization schemes. A parallel focus onunderstanding the effects of observational filtering willensure the comparability of the observations from thevarious instruments. To achieve this, the project will: -Expand the base of gravity-wave observations relevant togravity-wave parameterization schemes. This will principallyuse the suite of instruments at Davis ; - Use past and presentobservations to measure gravity-wave source characteristicsboth directly and by employing ray-tracing techniques to

relate middle atmosphere waves to source regions lower inthe atmosphere; - Measure the vertical flux of horizontalmomentum due to gravity waves above Davis; - Verify itsdominant role in the atmosphere’s momentum budget; and -Relate these observations to gravity-wave parameterizationschemes through comparison with model output.Enhancements to our current capabilities are planned: Agravity-wave ray-tracing capability will be developed; Theexisting meteor radar at Davis will be upgraded to allowmeasurements of the momentum flux in the MLT; and anairglow imager will be installed to allow high resolutionimages of gravity waves to be collected. Observations ofgravity-wave source characteristics, ray path distributionsand a climatology of momentum flux will be provided to themodelling community both directly and through the peer-reviewed literature. Collaboration with developers of theNOGAPS-ALPHA model will allow direct comparison ofparameterization scheme outputs to our observations. Thislink (and engagement with other interested modellinggroups) will aid in the development of the next generation ofparameterization schemes, mindful of the complexrelationship between the parameterization scheme and therest of the model.

Narayanan, Viswanathan L.Case study of a mesospheric wall wave eventNarayanan, Viswanathan L.1; Gurubaran, Subramanian1;Emperumal, Kaliappan1; Patil, Parashram T.2

1. Equatorial Geophysical Research Laboratory, IndianInstitute of Geomagnetism, Tirunelveli, India

2. Radar Observatory, Indian Institute of Geomagnetism,Shivaji University Campus, Kolhapur, India

Intense frontal features associated with gravity wavesaccompanying intensity variations in the airglow imageswere observed in the past and explained on the basis ofmesospheric bore theory or wall wave theory. Most of suchobservational features were explained as mesospheric boreswhile wall wave interpretations are rare. On the night ofFebruay 2, 2008, airglow imaging observations made fromPanhala (17°N, 74.2°E) showed signature of an intensegravity wave in OH, Na and OI green line emissions.Observations revealed passage of four frontal systemsseparated by ~325 km with an approximate time gap of~100 minutes between passage of alternate bright and darkfeatures. The intensity variations were nearly in phasebetween OH and Na images while out of phase with OIgreen line images. The first three fronts had horizontalextent covering entire field of view while the fourth one wasrelatively weaker and curved. The bright fronts (in OH andNa) showed evolution of phase locked trailing wave crestswith ~15 to 25 km wavelength while the dark fronts (in OHand Na) were devoid of such features. The alternating brightand dark phases of the fronts appear to indicate the crestsand troughs of a long period large amplitude gravity wavewhich might have given rise to evolution of short scale phaselocked crests in certain occasions. Thus, this observationsuggests possible generation of bores by means of wall waveperturbations. In this work we have discussed the

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characteristics of the event with background wind data fromco-located MF radar and snapshot temperaturemeasurements made by SABER instrument on boardTIMED satellite. Also discussion on the probable source ofthe observed wave is made.

Narayanan, Viswanathan L.Characteristics of high frequency gravity waves inthe upper mesosphere observed in OH nightglowover low latitude Indian sector during 2007Narayanan, Viswanathan L.1; Gurubaran, Subramanian1

1. Equatorial Geophysical Research Laboratory, IndianInstitute of Geomagnetism, Tirunelveli, India

Small scale high frequency gravity waves are believed toplay a vital role in the upper mesospheric region by means ofwave breaking and their interactions with other waves andbackground mean flow. They are known to propagate largedistances from their source regions by means of ductingwhich makes identification of their source distribution achallenging task. Further, their global distribution is not yetwell known. In this work we have studied the characteristicsof such high frequency waves observed in OH Meinel bandemissions over Tirunelveli (8.7°N, 77.8°E) during the year2007. The study reveals predominance of meridionallypropagating waves, possibly indicating the wind filteringeffects in the lower atmosphere. During summer period,waves propagating towards south and south-west wereobserved much more frequently. The apparent phasevelocities of the waves are higher during equinox periodsfollowed by summer and winter solstices respectively. Therewas no significant variation in the wavelength range of theobserved waves. Detailed discussion on the characteristics ofthe observed waves and possible source distributions aroundthis site during different seasons are made in this study.

Nath, DebashisCharacterization of the sources of Gravity Wavesover the Tropical Region, using High ResolutionMeasurementsNath, Debashis1; Venkat Ratnam, M.1

1. National Atmospheric Research Laboratory, Tirupati,India

An attempt has been made to investigate the dominantsource mechanisms for the generation of gravity waves ofdifferent scales over a tropical station like Gadanki (13.5oN,79.2oE) using high-resolution GPS radiosondemeasurements for inertia gravity waves. The high passfiltered profiles with a cut off > 3 days are subjected to leastsquare fit to extract the dominant vertical wavelength andthen different wave parameters like horizontal wavelength,vertical and horizontal phase speed, vertical and horizontalphase propagation direction etc. are estimated fromhodographs. It is well known that convection, wind shear(vertical shear of horizontal wind) and topography aredominant sources for the generation of gravity waves overthe tropics. Apart from these, horizontal shear of horizontal

wind (i.e. geostropic adjustment/spontaneous imbalance injets) is also a probable source for Inertia period gravity waves.Lagrangian Rossby Number shows high value over theobservational site indicating the role of GeostropicAdjustment for the generation of Inertia Gravity waves.Although Geostropic Adjustment is a frequent phenomenonover midlatitudes, but this is the first time report over thetropical region. During southwest monsoon season (June-August), over Indian region both convection and wind shearco-exists but upper tropospheric wind shear is foundresponsible for the generation of GWs on various scales,whereas convection mainly generates the high frequencygravity waves. Availability of long term GPS radiosonde datamotivated us to study the seasonal characteristics of inertiagravity wave. Clear semi-annual variation in inertia gravitywave energy with maximum during monsoon and winterand minimum during pre- and post-monsoons in thetroposphere is noticed during 2006 and 2008 but not clearin 2007. Annual variation is observed in the lowerstratosphere with maximum during monsoon (winterenhancement is not significant) season. This kind of winterenhancement in the troposphere is not expected at thistropical site but the contribution of meridional wind to thetotal kinetic energy is prominent. At the lower stratosphericheight waves are propagating mainly eastward, indicates theselective filtering of westward propagating gravity waves dueto strong shear. In addition, to understand the spatialcharacteristics of gravity wave and wave mean flowinteraction over the tropical region COSMIC GPS RadioOccultation data are used. Space-time spectra have beenconstructed from the symmetric and antisymmetriccomponent of temperature perturbations centered on theequator to extract the contribution due to gravity wave. Theinteraction of background wind shear due to QBO becomesimportant in the lower stratosphere, which modifies thepotential energy (EP) distribution at lower stratosphere. Themagnitude of stratospheric EP is ~ 10 J/Kg over Gadankiand is more prominent in the eastward wind phase of QBO,which matches fairly well with ground based observations.

Nielsen, KimImaging of Mesospheric Gravity Waves at HighLatitudesNielsen, Kim1; Collins, Richard2; Taylor, Michael3

1. Computational Physics, Inc, Boulder, CO, USA2. Geophysical Institute, Fairbanks, AK, USA3. Physics, Utah State University, Logan, UT, USA

As part of a collaborative effort between ComputationalPhysics Inc. (CPI), Utah State University (USU), andUniversity of Alaska, Fairbanks (UAF), an airglow imager isto be deployed over a three year period at Poker FlatResearch Range (PFRR), with expected data acquisition tobegin November, 2010. PFRR is ideally situated in theinterior of Alaska with long, dark winter nights exhibitingsignificant number of clear nights for premium opticalobservations. The site is surrounded by mountainousregions to the south (Alaska Range) and the north (White

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mountains and Brooks Range), which all are strong sourcesof orographic waves. Furthermore, PFRR is home to animpressive suite of atmospheric sensing instrumentscovering regions from ground and up through thethermosphere. The main focus of this project is tocharacterize the mesospheric gravity wave field at a highnorthern latitude, under various tropospheric conditions. Ofparticular interest are the effects of two very distinct weathersystems: the Aleutian low and the winter polar vortex,including effects of stratospheric warming events. Theimager is expected to provide an essential data set tounderstand the coupling mechanisms between the highlatitude lower and upper atmosphere. We will present hereresults obtained during the inaugural period.

Noel, VincentImpact of Gravity Wave events on the properties ofPolar Stratospheric Clouds over Antarctica fromspaceborne lidar observationsNoel, Vincent1; Chepfer, Helene2; Albert, Hertzog2

1. LMD, IPSL/CNRS, Palaiseau, France2. LMD, UPMC, Paris, France

The formation and properties of Polar StratosphericClouds (PSCs) are extremely dependent on their formationtemperature. Depending on the stratospheric concentrationsof chemical species, various temperature thresholds definePSC composition: Nitric Acid Trihydrate (NAT) or SulfuricTernary Solutions (STS) particles, ice crystals, or a mixturethereof. Most notably, ice-based PSCs (Type II in lidarobservation terminology) require colder temperatures thanNAT- or STS-based PSCs (Type Ia and Ib). On the otherhand, ice-based PSC form in a relatively short time, whileother PSCs require temperature to stay below theirformation threshold for a much longer period (days orweeks). During the Antarctic winter, stratospherictemperatures are generally in a range conducive to theformation of Type Ia and Ib PSCs, even if their dominantnucleation mechanisms are still not well understood. Type IIPSCs are rarer overall, as temperatures cold enough for theirformation is less frequent. This description based ontemperature is generally considered sufficient to explain thespatial and temporal distribution of PSCs. A recent theoryhowever suggests that ice-based PSCs might play a moresubstantial role in the formation of NAT- and STS-basedPSCs. According to the mountain-wave seeding hypothesis,ice-based PSCs form quickly following intense temperaturedrops due to gravity wave events propagating in the mid-stratosphere ; melting ice crystals exiting the gravity waveregion then act as the basis for fast NAT nucleation. NATparticles are then widely disseminated around the Antarcticcontinent by the strong winds of the polar vortex. We aim tostudy the validity of this hypothesis by evaluating the impactof gravity wave events on the population of PSCs. PSCobservations will be presented from the spaceborne lidarCALIOP, which is able to identify PSC altitude andcomposition with high accuracy. These observations will becorrelated with high-resolution mesoscale simulations over

the Antarctic peninsula and extensive time periods to detectgravity wave events and evaluate their importance on PSCproperties over the course of a full PSC season.

Ohno, TomokiA new estimation method of the momentum fluxesassociated with gravity waves: An application togravity-wave-resolving general circulation modeldataOhno, Tomoki1; Sato, Kaoru1; Watanabe, Shingo2

1. Department of Earth and Planetary Science, GraduateSchool of Science, University of Tokyo, Tokyo, Japan

2. Frontier Research Center for Global Change, JapanAgency for Marine-Earth Science and Technology,Yokohama, Japan

The momentum flux associated with gravity waves is animportant quantity to evaluate their effects on globalcirculations. As the gravity waves have various sources, it islikely that multiple gravity waves propagating in differentdirections are usually superposed. In such situation, even ifall physical quantities are available, it is difficult to estimatethe total momentum flux of gravity waves (i.e., a sum ofabsolute values of momentum fluxes of respective waves). Inthe present study, a new formula was derived to estimate thetotal momentum fluxes. This theoretical formula containsvariances of three dimensional wind and temperaturefluctuations and includes neither wavenumbers norfrequencies explicitly. This formula requires that wave fieldsare decomposed into monochromatic waves. Themomentum fluxes were estimated by applying this formulato a gravity-wave resolving general circulation model data.The model has T213 spectral horizontal resolution and 256vertical levels extending from the surface to a height of 85km with a uniform vertical spacing of 300 m in the middleatmosphere (Watanabe et al., JGR, 2008). As no gravity waveparameterization is used, all gravity waves in the model arespontaneously emitted from sources (convections,topographies, instabilities, jet imbalances, etc). Watanabe etal. showed that the model represents realistic generalcirculation and thermal structure in the middle atmosphere.Disturbances whose horizontal wavenumbers are greaterthan 26 are defined as gravity waves. Estimation was madefor the following 3 cases whose degree of monochromaticwave assumption at each grid is different: 1) Thefluctuations are assumed to be due to a monochromaticgravity wave. 2) The fluctuations can be decomposed only byvertical wavenumbers. 3) The fluctuations can bedecomposed by both vertical wavenumbers and frequencies.The resultant momentum fluxes from 2) and 3) are similar,while those from 1) and 2) are largely different, suggestingthat gravity waves could be decomposed intomonochromatic waves only by vertical wavenumbers.Moreover, following previous studies such as super pressureballoon observations (such as VORCORE), the vertical andtime average of the product of horizontal and vertical windfluctuation components was calculated and compared withthe estimate from the new formula. The result accords well

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with those from 2) and 3). This means that this simplemethod used in the previous studies gives reasonable results.Furthermore, the absolute momentum fluxes were dividedinto components in 4 directions and the geographicdistributions were examined. The result is shown in thetable,which is consistent with the result of net momentumfluxes distributions shown by Sato et al. (GRL, 2009).

Contribution of respective components to the total momentumfluxes

Orsolini, Yvan J.The roles of gravity and planetary waves during amajor stratospheric sudden warming characterizedby an elevated stratopauseOrsolini, Yvan J.1; Limpasuvan, Varavut2; Richter, Jadwiga B.3

1. Norwegian Institute for Air Research, Kjeller, Norway2. Coastal Carolina University, Conway, SC, USA3. NCAR, Boulder, CO, USA

Stratospheric sudden warmings (SSWs) contributesignificantly to the inter-annual variability of the wintertimepolar middle atmosphere, and couple the stratosphericcirculation with that of the mesosphere, as well as that ofthe troposphere. During SSWs, the separation of the winterpolar stratopause has long been recognized as a gravity wave(GW) driven feature, and GWs play a large role in theobserved mesospheric coupling. While historicalobservations have demonstrated that the polar stratopauseplunges down during the onset of SSWs, recent satelliteobservations further reveal that SSWs can be accompaniedby an abrupt “jump”, or reformation, of the stratopause near75km, at what are normally mesospheric altitudes. Thereformed stratopause then descends to its climatologicalaltitude over a period of 1-2 months as the polar vortexrecovers. We show evidence of such stratopause “jumps” inmesospheric temperatures from microwave observationsfrom the Odin satellite. We analyze cases of SSWssimulations of the National Center for AtmosphericResearch (NCAR) Whole Atmosphere Community ClimateModel (WACCM3.5), which show a realistic SSW occurrencefrequency. The planetary and gravity wave forcings areexamined in detail using the Transform Eulerian Meandiagnostic. We investigate the respective roles ofparametrized orographic and non-stationary (frontal orconvective) GWs, during the development of the SSW and ofthe zonal wind reversal, and demonstrate that eastward GWsof frontal origin and planetary waves play key roles duringthe stratopause reformation at high altitudes. The impact onthe residual circulation in the opposite, summer hemisphereis discussed.

Orsolini, Yvan J.Mesoscale Simulations of Gravity Waves during the2009 Major Stratospheric Sudden WarmingLimpasuvan, Varavut1; Alexander, M. J.2; Orsolini, Yvan J.3;Wu, Dong L.4; Xue, Ming5; Richter, Jadwiga H.6; Yamashita,Chihoko6

1. Chemistry and Physics, Coastal Carolina University,Conway, SC, USA

2. Colorado Research Associates Division, NorthwestResearch Assocaites, Boulder, CO, USA

3. Norwegian Institute for Air Research, Kjeller, Norway4. NASA Jet Propulsion Lab, Caltech, Pasadena, CA, USA5. University of Oklahoma, Norman, OK, USA6. NCAR, Boulder, CO, USA

A series of 24-hour mesoscale simulations (of 10-kmhorizontal and 400-m vertical resolution) are performed toexamine the characteristics and forcing of gravity waves(GWs) relative to planetary waves (PWs) during the 2009major stratospheric sudden warming (SSW) event. Just priorto SSW occurrence, widespread GW activities are foundalong the vortex’s edge and associated predominantly withmajor topographical features and strong near-surface winds.Momentum forcing due to GW surpasses PW forcing in theupper stratosphere and tends to decelerate the polar westerlyjet in excess of 30 m s-1 day-1. With SSW onset, PWsdominate the momentum forcing, providing decelerativeeffects in excess of 50 m s-1 day-1 throughout the upperpolar stratosphere. GWs related to topography become lesswidespread largely due to incipient wind reversal as thevortex starts to elongate. During the SSW maturation andearly recovery, the polar vortex eventually splits and bothwave signatures and forcing greatly subside. Nonetheless,during SSW, propagating GWs are found in the polar regionand may be generated in situ by flow adjustment processesin the stratosphere or by wave breaking. The simulated large-scale features agree well with those resolved in satelliteobservations and analysis products.

Ortland, DavidOn the interaction of the migrating diurnal tidewith inertia gravity waves generated by tropicalheatingOrtland, David1; Alexander, M. Joan2

1. NorthWest Research Associates, Redmond, WA, USA2. NWRA, Colorado Research Div., Boulder, CO, USA

High resolution data of rainfall rate and infrared cloudtop brightness temperature derived from the TropicalRainfall Measuring Mission have been used to constructestimates of latent heating and cloud top height every 3hours on a .25 x .25 longitude-latitude grid. This heating isused to force a global time-dependent model that includesthe mesosphere and lower thermosphere, from which westudy the spectrum of wave motion produced in response tothe heating. The main component of the wave spectrum thatremains in the mesosphere consists of inertia gravity waves

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(IGW) and Kelvin waves with phase speed greater than 40m/s. We also realistically force the migrating diurnal tide inour model and study the interaction of the IGW spectrumwith the tides. We find that the IGWs significantly impactthe amplitude and structure of the tide. Model simulationsin which the wave spectrum is filtered throughclimatological mean winds derived from UARS observationsdo not reproduce the strong seasonal and interannual(quasi-biennial) variations in the amplitude of the migratingtide that are observed. We shall compare the modulation ofthe resolved IGW spectrum by the tide winds to themodulation predicted by the Alexander-Dunkertonparameterization scheme for small-scale gravity waves.

Pangaluru, KishoreStudy of gravity wave activity in the troposphereand lower stratosphere using the GPS satelliteobservationsPangaluru, Kishore1; Velicogna, Isabella1, 2

1. Earth and System Science, University of California,Irvine, CA, USA

2. California Institute of technology, Jet propulsionLaboratory, Pasadena, CA, USA

It is now well confirmed that gravity waves play a crucialrole in determining the circulation and mean state of theatmosphere. In recent years a significant effort has beenmade in quantifying the general characteristics of lower andmiddle atmosphere gravity waves. Satellite observationsprovide a valuable source for gravity wave studies in thelower and middle atmosphere, especially over oceans andother radiosonde-sparse regions. GPS satellites provideglobal atmospheric profiling with high vertical resolution(0.1-1 km) and high accuracy under all weather conditions.The present study considers a data sample for 89 monthsthat begins from June 2001 to October 2008 for CHAMPand 50 months from May 2006 to June 2010 for COSMICoccultation data sets. Potential energy (Ep) are evident at 20-30 km; in particular, Ep values are highly enhanced near theequator.

Pfister, LeonhardThe Effects of Subgrid Scale Gravity Waves onWater Vapor and Clouds in the TropicalTropopause LayerPfister, Leonhard1; Jensen, Eric1

1. NASA Ames Research Center, Moffett Field, CA, USA

Previous work has shown that horizontal motionthrough cold regions in the Tropical Tropopause Layer(TTL) is the critical mechanism for dehydrating the airentering the stratosphere. Large scale cold regions (forexample, the cold pool at 100mb over the Western Pacific inboreal winter) play the largest role. However, previous workby the authors has shown that small scale motions that arenot realized in analyses are important for both water vaporand clouds. By making cold temperatures and saturationmore frequent at higher altitudes, sub grid scale motions (in

the TTL and stratosphere these are almost exclusivelyinertia-gravity waves) effectively raise the level ofdehydration, reduce water vapor in the upper TTL, andincrease the incidence of clouds. The latter are importantbecause of their effect on the radiation budget and theoverall temperature of the TTL. Previous inclusions of sub-grid scale motions have relied on longitude-independentstatistical spectral models of the gravity wave motions. Inthis paper, we reexamine the role of gravity waves ingoverning TTL water vapor and clouds using a trajectory-based microphysical model in the light of: (1) more recentradiosonde data on waves in the lower TTL, (2) more recent,higher resolution global meteorological analyses, and (3)different microphysical nucleation schemes more consistentwith observed cloud data. We also explore theimplementation of longitude-dependent statistical models.

Plougonven, RiwalNon-orographic and orographic sources of gravitywaves above Antarctica and the Southern Ocean(INVITED)Plougonven, Riwal1; Hertzog, Albert2; Guez, Lionel1

1. Laboratoire de Meteorologie Dynamique, Ecole NormaleSuperieure, Paris, France

2. Laboratoire de Meteorologie Dynamique, EcolePolytechnique, Palaiseau, France

A major weakness of Gravity Wave (GW)parameterizations is the representation of sources, inparticular non-orographic ones. These are most oftenarbitratily set, and tuned to yield a satisfactory circulation inthe middle atmosphere. This stems both from our lack ofphysical understanding of the mechanisms involved, inparticular GW radiation from jets and fronts, and frominsufficient constraints from observations and modelling.We will present results from meso-scale simulations coveringtwo months (October 21 to December 18, 2005) for adomain covering Antarctica and the Southern Ocean (10,000x 10,000 km, with a resolution dx = 20 km). Thesesimulations contribute to both endeavours: - they constitutea realistic counterpart to the idealized baroclinic life cycleswhich have strongly contributed over the past fifteen yearsto our understanding of GW radiation from jets; - theycomplement the Vorcore observational campaign, duringwhich 27 superpressure balloons were launched into thestratospheric polar vortex (September 2005-Januray 2006).The first issues investigated in these simulations are: 1- howcomparable are the simulated GW relative to the balloonobservations from the Vorcore campaign? 2- how similar arenon-orographic waves in these real-case simulations to thosefound in idealized baroclinic life cycles? In answer to 1, itappears that the simulations succeed in capturing the overalldistribution of momentum fluxes due to GW in the lowerstratosphere, with a distinct maximum over the AntarcticPeninsula, yet these fluxes are somewhat underestimatedrelative to the estimations from the balloons. The resolutionused (dx=20km) is generally insufficient for a detailledcomparison to be made for individual wave packets. To test

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the sensitivity to resolution, nine days were simulated withdoubled horizontal resolution. Momentum fluxes are nearlydoubled, most of the changes affecting the vertical velocity(finer structure, enhanced amplitudes). In agreement withVorcore observations, the overall contribution from oceanicregions is comparable to that from regions with orography,but intermittency is far greater over the latter. Thecomparison also sheds new light on the uncertainties andlimitations of the estimations made from Vorcoremeasurements. In answer to 2, the real case simulations doshow cases of gravity waves present in jet exit regions, withwave capture playing a role, similar to the configurationemphasized in several studies of idealized simulations(baroclinic waves and dipoles). However, the wave field hassignificantly greater complexity than that analyzed in theidealized simulations, indicating that contributions fromother generation mechanisms need to be taken into account.The third set of questions we can investigate in thesesimulations concern the sources: what diagnostic from thelarge-scale flow is relevant to quantify emission from jetsand fronts? How wide an area is affected by wavesoriginating from mountains, including through secondarygeneration? Preliminary results on these issues will bediscussed.

http://www.lmd.ens.fr/plougon/

Plougonven, RiwalGravity waves emitted from jets: lessons fromidealized simulationsPlougonven, Riwal1; Snyder, Chris2; Lohrey, Steffen1

1. Laboratoire de Meteorologie Dynamique, Ecole NormaleSuperieure, Paris, France

2. National Center for Atmospheric Research, Boulder, CO,USA

A longstanding problem in the description of gravitywave sources concerns waves emitted from jets and fronts.Theoretical studies of mechanisms of spontaneousgeneration suggest that the emission is expected to beexponentially weak in Rossby number, yet the mechanismsdescribed (e.g. mixed instabilities involving baanced andunbalanced motions) do not seem to explain the emissionobserved and simulated near jets. From observations, it hasbeen known for some time that jet exit regions often exhibitintense inertia-gravity waves, suggesting generation there.Simulations of idealized baroclinic life cycles have confirmedthe specific role of these jet exit regions and shown thatspecific processes for propagation (i.e. ‘wave capture’) play animportant role there. The generation and subsequentpropagation of waves at the front of upper-tropospheric jetstreaks has been shown to be analogous to what happens ina dipole, yet the latter is, attractively, much simpler andallows a detailled understanding of the generationmechanism. This poster will focus on recent advances onwave excitation in a dipole and in nine baroclinic life cycles.The generation of inertia-gravity waves in the front of adipole has been explained as the linear response, within abalanced background dipole flow, to the small discrepancies

between the balanced and the full tendencies for wind andpotential temperature. It is worth emphasizing that it iscrucial to linearize around a background dipole flow, as thestructure of the waves that are generated (i.e. concentrationin the jet exit region, phase lines transverse to the flow there,small horizontal scales) comes almost entirely from theresulting non-trivial, non-constant coefficient linearoperator. Past studies have seeked to isolate a diagnosticfrom the large-scale flow that could be indicative of thelocation and intensity with which gravity waves aregenerated (e.g. Lagrangian Rossby numbers, residual of theNonlinear Balance Equation). The relevance of thesediagnostics is tested in both dipole and idealized baroclinicwave simulations. Regarding location, they are not alwaysfound to indicate the dynamically significant regions of theflow. An indicator such as the Okubo-Weiss parameter,which highlights regions of strong strain without vorticity, isfound to better isolate jet exit regions where waves tend to becaptured. Regarding amplitudes, such indicators are byconstruction linear or quadratic in the dipole strength or asthe square of the dipole strength. The emission was notfound to follow such a simple scaling law. On the contrary, itrather seems to ‘turn on’ at a certain finite Rossby number,as could appear if waves are exponentially small in Rossbynumber. This behavior can be explained if we take intoaccount the advection by the flow past the forcing term. Asthe dipole strength increases, it is not only the intensity ofthe forcing which increases, but also the advection past thisforcing. As a result, a larger part of the spectrum contributesto wave generation. A nonlinear dependence of waveamplitude on the intensity of the dipole is thus obtained,qualitatively similar to what was found in simulations.

http://www.lmd.ens.fr/plougon/

Prasanth, Vishnu P.LiDAR observations of middle atmospheric gravitywave activity over Reunion Island (20.8°S,55.5°E): Climatological studyPrasanth, Vishnu P.1; Bencherif, Hassan2; Kumar, Siva3;Keckhut, Philip4; Hauchecorne, Allain5

1. Department of Physics, Sree Vidyaniketan EngineeringCollege, Tirupati, India

2. Laboratoire de l’Atmosphere et des Cyclones, Universitede La Reunion, Reunion, France

3. National Laser Centre, Council for Scientific andIndustrial Research, Pretoria, South Africa

4. Laboratoire Atmosphères Milieux Observations Spatiales,France, France

5. Laboratoire Atmosphères Milieux Observations Spatiales,France, France

In this Paper, climatological characteristics of thegravity wave activities are studied using temperature profilesobtained from Rayleigh lidar located at Reunion Island(20.8°S, 55°E) over a period of ~14 years (1994-2007).Gravity wave (GW) study has been performed over the heightrange from 30 to 65 km. The present study documents theGW characteristics in terms of time (frequency), height (wave

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number) and GW associated Potential Energy and theirseasonal dependences. Generally, the temporal evolution oftemperature profile illustrates the downward phasepropagation indicating that the energy is propagatingupward. The wave activity is clearly visible with the waveperiods ranging from 260 min to 32 min. The dominantcomponents have vertical wavelengths in the range of about~4 km to 35 km. The potential energy over the height regionfrom 30 km to 65 km are calculated and presented. It isfound that the seasonal variation of potential energy ismaximum during summer in the upper stratosphere andlower mesosphere. A semiannual variation is seen in thegravity wave activity over all height ranges in the months ofFebruary and August.

Preusse, PeterEffects of oblique gravity-wave propagation onmiddle-atmosphere forcing (INVITED)Preusse, Peter1; Kalisch, Silvio1; Ern, Manfred1; Eckermann,Stephen D.2

1. IEK-7, Forschungszentrum Juelich GmbH, Juelich,Germany

2. E.O. Hulburt Center for Space Research, Naval ResearchLaboratory, Washington DC, DC, USA

The current generation of GCMs used for climateprediction rely on gravity wave (GW) parameterizations fortaking into account mean-flow acceleration by GWdissipation. Conventional GW parameterizations considervertical propagation only. We perform an offline study withprescribed background winds and a spectral sourcedistribution tuned to satellite GW measurements. Runs withpure vertical and full three-dimensional oblique wavepropagation are performed. The effects of oblique wavepropagation on the GW-induced acceleration of the meanflow and of planetary waves are discussed.

Preusse, PeterThe ESA gravity wave studyPreusse, Peter1; Hoffmann, Lars1; Ma, Jun2; Hoefer,Sebastian1; Hertzog, Albert3; Alexander, M. J.4; Broutman,Dave2; Bittner, Michael13; Chun, Hye-Yeong5; Dudhia, Anu6;Ern, Manfred1; Hoepfner, Michael7; Kim, So-Young5; Lahoz,William8; McConnell, John C.9; Pulido, Manuel10; Remedios,John11; Sembhi, Harjinder11; Semeniuk, Kirill9; Sofieva,Viktoria12; Wüst, Sabine13; Orphal, Johannes7; Riese, Martin1

1. IEK-7, Forschungszentrum Juelich, Juelich, Germany2. Computational Physics Incorporated, Springfield, VA,

USA3. Laboratoire de Meteorologie Dynamique, Ecole

Polytechnique, Palaiseau Cedex, France4. CoRA Division, NorthWest Research Associates, Boulder,

CO, USA5. Dept. of Atmospheric Sciences, Yonsei University, Seoul,

Republic of Korea6. Dept. of Physics, University of Oxford, Oxford, United

Kingdom7. IMK, Karlsruhe Institute of Technology, Karlsruhe,

Germany8. Norsk Institutt for Luftforskning, Kjeller, Norway9. York University, Toronto, ON, Canada10. Universidad Nacional del Nordeste, Corrientes, Argentina11. University of Leicester, Leicester, United Kingdom12.Finnish Meteorological Institute, Helsinki, Finland13.Deutsches Zentrum fuer Luft- und Raumfahrt, Wessling,

Germany

New detector technology has matured in recent yearsand now allows an instrument to be built which can measureatmospheric trace species and temperature from orbit withunprecedented three-dimensional spatial resolution. Theability of such an infrared limb imager to resolve gravitywaves (GWs) is assessed in a study sponsored by theEuropean Space Agency (ESA) and the following questionsare addressed: * can high-resolution temperaturemeasurements be processed to infer GW momentum flux? *how does the validity or otherwise of WKB and polarizationrelations affect such calculations? * how does the spatialobserving geometry influence: — the separation of GWsfrom the global background — GW amplitudes, horizontaland vertical wavelengths * which waves are visible to theinstrument We assess these questions by end-to-endsimulations of measurements and GW products. Thepotential of a new mission to measure GWs using infraredlimb imaging will be summarized based on thesesimulations, and compared to existing GW-measurementtechniques, such as satellite, ground-based and in-situ.

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Pulido, ManuelA Comparison of Gravity Wave DragParameterizations using Inverse TechniquesScheffler, Guillermo1; Pulido, Manuel1

1. Department of Physics, Universidad Nacional delNordeste, Corrientes, Argentina

This work attempts to make a comparison betweendifferent gravity wave drag parameterizations. To perform athroughout comparison two inverse techniques are used.The inverse techniques offer a robust framework to performthe drag comparison: for a given ‘observed’ gravity wavedrag, the inverse techniques estimate the optimal parametersand therefore the optimal gravity wave drag given by eachparameterization. In this way the error of eachparameterization can be inferred. The estimation of optimalparameters is performed with two different inversetechniques: the genetic algorithm and the ensemble Kalmanfilter. We show that the parameter estimation can be carriedout efficiently using both inverse techniques. An hydrostaticnon-rotational version of Scinocca gravity wave drag schemeand a version of the Warner & McIntyre ultra-simple spectralgravity wave drag scheme are used as parameterizationschemes. The ‘observed’ gravity wave drag used in this workis the one estimated in Pulido & Thuburn 2008. For bothparameterizations, the impact on the drag field of usingoptimal parameters compared to the use of standard tunedvalues is shown. In general, Scinocca parameterization gets acloser match to the ‘observed’ gravity wave drag usingoptimal parameters. Both parameterizations do not presenta realistic drag in the lower tropical stratosphere. The inversetechnique based on the ensemble Kalman filter is a feasibledata assimilation technique to be implemented in a fullGCM due to its low computational cost.

Pulido, ManuelEstimation of Optimal Gravity Wave Parametersfor Climate Models using a Hybrid Genetic-Variational Technique (INVITED)Pulido, Manuel1

1. Department of Physics, Universidad Nacional delNordeste, Corrientes, Argentina

There is a current need to constrain the parameters ofgravity wave drag schemes of climate models usingobservational information instead of tuning themarbitrarily. An inverse technique is presented to estimateparameters from gravity wave schemes. We define a costfunction that measures the differences between the zonaland meridional components of the ‘observed’ gravity wavedrag field and the gravity wave drag calculated with ascheme. The proposed inverse technique is composed by agenetic algorithm and a variational assimilation techniquebased on conjugate gradients. The first is used to estimate aclose enough first guess and then conjugate gradients isapplied. It is concluded that the parameter estimation usingthis hybrid technique is robust over a broad range of

prescribed ‘true’ parameters. Estimations using ‘observed’gravity wave drag from Pulido and Thuburn (2008) areperformed, the gravity wave drag given by theparameterization for an optimal set of global parametersdoes not reproduce the observed features. On the otherhand, if the parameters are allowed to vary with the latitude,a good fit of the observed gravity wave drag is obtained,except at the tropical lower stratosphere. In this region somerelaxations of the parameterization are proposed in order tohave a better agreement with the forcing needed to drive theQBO. Simulations with the dynamical stratosphere modelusing the optimal parameters are performed, an importantreduction of the model error is obtained.

Reeder, Michael J.Nonlinear Processes and Their Role in theGeneration of Gravity Waves by Convective ClouldLane, Todd P.2; Reeder, Michael J.1

1. Monash University, Clayton, VIC, Australia2. University of Melbourne, Melbourne, VIC, Australia

Convective clouds generate gravity waves and thesewaves are known to have important influences on themomentum budget of the middle atmosphere. Significantadvances in our understanding of the wave generationprocess and the resultant spectrum have been achieved inthe last decade using theory, models, and observations. Oneoutcome of this understanding has been the development ofa number of new parameterizations of the source spectrumof convectively generated gravity waves for use in generalcirculation models. These source parameterizations areultimately based on the linear response to imposed diabaticheating. However, previous studies have shown thatnonlinearities within convective clouds play an importantrole in defining the wave spectrum. In this study, we focusour attention on the characteristics and dynamics of thesenonlinearities. In particular, a set of idealized linear andnonlinear models forced by an imposed diabatic heat sourceare used to explore the role of nonlinearities in the wavegeneration process. These simulations clearly show that thenonlinearities play the key role in the production of gravitywaves that have frequencies close to the Brunt-Väisäläfrequency. They also demonstrate that the fully nonlinearwave spectrum is readily reproduced using a weaklynonlinear source formulation. The implications for theseresults for improving gravity wave source parameterizationswill also be presented.

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Sassi, FabrizioThe effect of temporal correlation on thepredictability of the MLT region in a stochasticnonorographic gravity wave drag parameterizationSassi, Fabrizio1; Eckermann, Stephen1; Hoppel, Karl2

1. Space Science Division, Naval Research Laboratory,Washington, DC, USA

2. Remote Sensing Division, Naval Research Laboratory,Washington, DC, USA

A stochastic parameterization of nonororgaphic gravity-wave drag (NGWD), recently developed at the NavalResearch Laboratory (Eckermann, 2011), is implemented inthe general circulation model that comprises the forecastmodel component of a high-altitude (0-100 km) prototypeglobal numerical weather prediction (NWP) system. Themodel’s default configuration uses the Whole AtmosphereCommunity Climate Model (WACCM) NGWDparameterization of Garcia et al. (2007) that uses adeterministic source spectrum with multiple waves. The newscheme simply replaces this deterministic multiwavediscretization of the source spectrum with a randomdiscretization governed by a single wave whose phase velocityis assigned randomly. While this stochastic parameterizationreproduces well the mean climate of the deterministicscheme, it also produces large variances in the mesosphereand lower thermosphere (MLT). In its original formulation,each random wave in the stochastic scheme is uncorrelatedin time. By running the NWP system with full 6-hourlyforecast and data assimilation (DA) update cycles, andintroducing perturbations to generate ensembles, weinvestigate how different levels of imposed temporal auto-correlation among parameterized stochastic waves affect thequality of the resulting MLT simulations, as judgedobjectively using NWP statistics based on the forecasts andverifying analysis fields. We specifically study how theintroduction of the stochastic scheme and different levels oftemporal auto-correlation affect MLT predictability forsolstice and equinox conditions.

Sato, KaoruProgram of the Antarctic Syowa MST/IS Radar(PANSY)Sato, Kaoru1; Tsutsumi, Masaki2; Sato, Toru3; Nakamura,Takuji2; Saito, Akinori3; Tomikawa, Yoshihiro2; Nishimura,Koji2; Yamagishi, Hisao2; Yamanouchi, Takashi2

1. Department of Earth and Planetary Science, University ofTokyo, Tokyo, Japan

2. National Institute of Polar Research, Tokyo, Japan3. Kyoto University, Kyoto, Japan

Syowa Station is one of the distinguished stations,where various atmospheric observations for researchpurposes by universities and institutes as well as operationalobservations by Japan Meteorological Agency and NationalInstitute of Information and Communications Technologyare performed continuously. National Institute of Polar

Research plays a central part in the operations. Theobservation of the Antarctic atmosphere is important in twosenses. First, it is easy to monitor weak signal of the earthclimate change because contamination due to humanactivity is quite low. Second, there are various uniqueatmospheric phenomena in the Antarctic having strongsignals such as katabatic flows, the ozone hole, noctilucentclouds, and auroras. The middle atmosphere is regarded asan important region to connect the troposphere andionosphere. However, its observation is sparse and retardedin the Antarctic compared with the lower latitude regions;nevertheless the vertical coupling through the mechanismssuch as momentum transport by gravity waves is especiallyimportant in the polar region. Since 2000, we have developedan MST/IS radar to be operational in the Antarctic and havemade feasibility studies including environmental tests atSyowa Station. Various significant problems have beenalready solved, such as treatment against low temperatureand strong winds, energy saving, weight reduction, andefficient construction method. A current configuration ofthe planned system is a VHF (47MHz) Doppler pulse radarwith an active phased array consisting of 1045 yagis. Thevalue of the PANSY project has been approvedinternationally and domestically by resolutions andrecommendations from international scientificorganizations such as IUGG, URSI, SPARC, SCOSTEP, andSCAR. The scientific research objectives and technicaldevelopments have been frequently discussed atinternational and domestic conferences and at a scientificmeeting at NIPR organized by the PANSY group every year.Special and union sessions of PANSY were organized atrelated scientific societies such as MSJ (MeteorologicalSociety of Japan), SGEPSS (Society of Geomagnetism andEarth, Planetary and Space Sciences) and JpGU (JapanGeophysical Union) to deepen the discussion. The PANSYproject was authorized as one of main observation plans forthe period of JARE52-57 in 2008, and funded by Japanesegovernment in 2009. We will start the radar construction inearly 2011. After one year for initial test observations,MST/IS observations will be made over 12 years whichcovers one solar cycle.

http://pansy.eps.s.u-tokyo.ac.jp

Sato, KaoruOn the mechanism of the formation of the Brewer-Dobson circulation and the change in the age of airSato, Kaoru1; Okamoto, Kota1; Akiyoshi, Hideharu2

1. Department of Earth and Planetary Science, TheUniversity of Tokyo, Tokyo, Japan

2. National Institute for Environmental Studies, Tsukuba,Japan

The stratospheric meridional distribution ofatmospheric minor constituents such as ozone is largelyaffected by the Brewer-Dobson circulation (BDC) consistingof upwelling in the low latitudes and downwelling in themiddle to high latitudes of each hemisphere. Thiscirculation is considered to be driven by the body force in the

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middle latitudes in the stratosphere induced by the breakingand/or dissipation of waves propagating mainly from thetroposphere. Previous studies indicate that planetary wavesare a main driver of the BDC. However, it is also recognizedthat the momentum deposition by synoptic-scale waves andgravity waves is important for the zonal momentum balancein the lower stratosphere. The purpose of this study is toquantify the relative role of each kind of waves to the BDCdriving mechanism. The contribution of different types ofwaves to the BDC in the Center for Climate SystemResearch/National Institute for Environmental Studies(CCSR/NIES) Chemistry Climate Model (CCM) for thepresent climate was diagnosed using the “downward controlprinciple (DC)”. Orographic gravity wave drag (OGWD) hasa great influence on the BDC in middle latitudes of thelower stratosphere. In addition, OGWD is a dominant factorto form the ascent in the summer low-latitude part of wintercirculation at all heights of the stratosphere. The DCanalysis was also applied to the ERA-Interim data. The resultis consistent with that of the CCM analysis. Thus, it isconcluded that the gravity waves play an important role inmaintaining the BDC. Moreover, we analyzed long-termchanges of the BDC by comparing the “age of air” (AOA)using CCM data for the recent past (1985), present (2005)and future (2085) climates. In this study, the AOA wasestimated by calculating backward trajectories from a givenlatitude and pressure level to the 100 hPa level in the residualvelocity fields that were obtained using the CCM data. Sincethe mixing processes by subgrid-scale motions are ignored inthe AOA estimates, the long-term change in the “AOA”should be explained by the change of the BDC. The AOA inthe future is smaller than that in the present, which isconsistent with the acceleration of the BDC as shown bysimulations using most CCMs under the scenario ofgreenhouse gases increase. However, the difference in AOAbetween the past and present climates depends on theregion. The difference is significantly positive in highlatitudes of the middle atmosphere, while it is negative inthe other regions of the stratosphere. In order to clarify thecause of the positive difference, namely larger AOA in thepresent climate than in the past, the trajectorycharacteristics were examined in detail. As a result, it turnedout that the larger AOA in the present climate is mostly dueto longer transport paths rather than slower speeds of theBDC. This result may explain the observational evidence oflittle or slightly positive AOA trend which is, at a glance, incontradiction to the positive trend in the BDC strengthshown by most CCMs.

Seker, IlginThe relation between the E-region gravity wavesand the F-region plasma depletions observed withan all-sky imager at AreciboSeker, Ilgin1; Fung, Shing F.1; Mathews, John D.2

1. NASA Goddard Space Flight Center, Greenbelt, MD, USA2. Electrical Engineering, The Pennsylvania State Univeristy,

University Park, PA, USA

At mid-latitudes, F-region plasma depletions calledplumes and medium scale traveling ionosphericdisturbances (MSTIDs) have been regularly observed withall-sky imagers using the 630 nm airglow emission. On theother hand, various types of gravity waves are commonlyobserved in the E-region using the 557.7 nm airglowemission. Atmospheric gravity waves (AGWs) havecommonly been suggested as a potential seeding mechanismfor F-region instabilities. Recent studies have discovered anelectrodynamic coupling between the E and F regions. Inthis study, we use 557.7 nm and 630 nm airglow data froman all-sky imager located at Arecibo Observatory (AO) tostatistically compare the occurrences of the E-region gravitywaves and the F-region plasma depletions (e.g., MSTIDs andplumes) during the period of 2003-2008. A correlation isobserved between the events in these two ionospheric layerssuggesting that the gravity waves are one of the majorseeding sources of the mid-latitude F-region irregularities.Example case studies when events in both layers have beenobserved simultaneously are also presented to comparevarious properties of gravity waves, plumes, and MSTIDs.

Sharma, Som KumarAtmospheric Gravity Wave Activity over a Sub-tropical and Tropical Indian LocationsSharma, Som Kumar1; Sridharan, S.2; Chandra, H.1; Lal, S.1;Acharya, Y.1

1. Physical Research Laboratory, Ahmedabad, India2. National Atmospheric Research Laboratory, Gadanki,

India

Gravity Waves (GWs) play an important role in energyand momentum transport from troposphere to the upperatmosphere. Nd: YAG laser based Rayleigh lidars are inoperation at Mount Abu, (24.5o N, 76.2o E) a sub-tropicalsite and at Gadanki (13.5o N, 79.2o E) a tropical site, inIndia. Strong convective activity over tropical and sub-tropical regions plays an important role for the generation ofGWs. Mt. Abu (24.5°N, 72.7 °E) is located in sub-tropical,hilly region where a large number of convective phenomenaoccur. The gravity wave characteristics are presented in termsof vertical wave number and frequency spectra, along withthe estimated potential energy for the winter and summer.The GWs study at Mt. Abu may contribute to a betterunderstanding of middle atmosphere on seasonal and longterm scales and in delineating vertical coupling betweenlower, middle and upper atmosphere. Rayleigh lidar is inoperation at Mt. Abu since 1997. We make use of ~11 years

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(1997-2008) of high resolution Rayleigh lidar measurementsfor the present study. Temperature profiles are derived fromraw data (photon count profiles) in the height range of 30-65 km with a vertical resolution of ~480 m. Temperatureprofiles are further analyzed to extract and delineate theGWs features. The present study is focused on the GWscharacteristics in terms of time (frequency) and height(wave-number), associated Potential Energy (P.E.) and theirseasonal dependences. The frequency and wave-numberspectra are obtained for about 250 days where continuousdata sets of ~4 hours are available. Generally, the temporalevolution of temperature profile illustrates the downwardphase propagation indicating that the energy is propagatingupward. The dominant time period of GW is found to begreater than 2.3 hours in the mesosphere at the 60-65 kmheight region. The lower periodicity of less than ~2 hoursare found in the upper stratosphere (30-45 km). The P.E. for3 different height regions (35-40 km, 45-50 km and 55-60km) are calculated and analyzed. The seasonal variation ofGWs characteristics and associated P.E. has also beeninvestigated. It shows two distinguished maxima during Mayand November months. The obtained results are comparedwith results obtained from tropical station. Furthermore,Lidars at Mt. Abu and Gadanki were operatedsimultaneously in coordinated fashion during the months ofMarch, April and May. Significant differences are found inthe day to day GW characteristics over sub-tropical andtropical locations. Detailed results will be presented anddiscussed.

Shaw, Tiffany A.The application of wave-activity conservation lawsto cloud resolving model simulations of multiscaletropical convection (INVITED)Shaw, Tiffany A.1, 2; Lane, Todd P.3

1. Lamont-Doherty Earth Observatory, ColumbiaUniversity, Palisades, NY, USA

2. Department of Applied Physics and AppliedMathematics, Columbia University, New York, NY, USA

3. School of Earth Sciences, The University of Melbourne,Melbourne, VIC, Australia

Pseudomomentum and pseudoenergy wave-activitydiagnostics are applied to cloud resolving model simulationsof multiscale tropical convection. Wave-activity conservationlaws are the relevant budgets to consider when examiningthe transfers of momentum and energy between adisturbance (the convection and waves) and a background(shear-stratified) flow. The vertical fluxes ofpseudomomentum represent those parameterized in climatemodels and include pseudomomentum transfers due toconvection (convective momentum transport) and gravitywaves (gravity wave drag). The wave-activity diagnosticsreveal that both non-conservative (diabatic) and transientprocesses contribute to the generation of the vertical fluxesof pseudomomentum and pseudoenergy. A spectraldecomposition reveals that each horizontal phase speedspectral element has a source region between the surface and

the uppermost cloud level with peaks associated withshallow through deep clouds and a sink region above. Thefluxes are subsequently separated into upward andnonupward propagating contributions to isolate thepseudomomentum transfer by convection from those due toupward propagating waves. The nonupward propagatingcontribution to the pseudomomentum fluxes is confinedbelow the cloud layer. The corresponding upwardpropagating contribution is large above and below the cloudlevel and highlights the importance of accounting for thesource region in gravity wave drag parameterizations. Theevolving convective organization is clearly seen in thetransience term both above and below the cloud layer. Theresults highlight important connections betweenpseudomomentum transfers due to convection and upwardpropagating waves.

Shibata, KiyotakaGravity wave drag effects on the future quasi-biennial oscillation in the tropical stratosphereunder greenhouse gas increase up to year 2100:Simulations with a chemistry-climate modelShibata, Kiyotaka1; Deushi, Makoto1

1. Meteorological Research Institute, Ibaraki, Japan

Simulations on the past and future middle atmospherewere made with the chemistry-climate model (CCM) ofMeteorological Research Institute (MRI), MRI-CCM. Themodel includes full stratospheric chemistry and simplifiedtropospheric chemistry. The model resolution is T42L68with top at 80 km and reproduces spontaneously the quasi-biennial oscillation (QBO) by incorporating a Hines gravitywave drag scheme, the period of which is about 27-month,being very close to the observed 28-month. Three differentforcing runs were performed for 140 years from 1960 to 2100without solar cycle and volcanic aerosols. The first run usesthe SRES A1B GHG scenario and the adjusted A1 halogenscenario. The second uses the same SRES A1B GHG scenariowith the halogens fixed at 1960 levels, and the third uses thesame adjusted A1 halogen scenario with the GHGs fixed at1960 levels. SST/sea-ice conditions are imposed to becompatible with the GHG scenarios. These runs correspondto CCMVal-2 reference simulations of REF-B2, andsensitivity simulations of SCN-B2b and SCN-B2c,respectively. It is found that the QBO amplitude in zonalwind in the tropical stratosphere is decreased in futureunder the global warming due to the greenhouse gasincrease, while the QBO amplitude is scarcely decreasedunder the fixed GHGs conditions.

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Sugimoto, NorihikoSpontaneous gravity wave radiation from unsteadyrotational flows in a rotating shallow water systemSugimoto, Norihiko1; Kobayashi, Hiromichi1; Shimomura,Yutaka1; Ishioka, Keiichi2

1. Keio University, Yokohama, Japan2. Kyoto University, Kyoto, Japan

Spontaneous gravity wave radiation from unsteadyrotational flows is investigated in a rotating shallow watersystem. It is well known that gravity waves play veryimportant roles on the middle atmosphere. They propagatefar away from the source region of the troposphere to themiddle atmosphere and drive global material circulation ofthe middle atmosphere by putting significant amount ofenergy and momentum flux. Recent observational studiessuggested that gravity waves are radiated from strongrotational flows, such as polar night jet, sub-tropical jet, andtyphoon. This radiation process is called as a spontaneousgravity wave radiation, since gravity waves are spontaneouslyradiated from initially balanced rotational flows. Althoughthere are several numerical studies, this process has not beenfully understood. In the previous studies, we investigatedspontaneous gravity wave radiation from unsteady jet flowin the most simplified system of shallow water that includesboth rotational flows and gravity waves. Figure 1 shows asnapshot of the spontaneous gravity wave radiation fromunsteady jet flow in a shallow water system on a rotatingsphere. The key point was that only gravity waves havinghigher frequency than the inertial cut-off frequency arespontaneously radiated from higher frequency tails ofunsteady rotational flows. Therefore, the effect of theEarth’s rotation greatly affects spontaneous gravity waveradiation and propagation. In the present study, weinvestigate spontaneous gravity wave radiation from co-rotating vortex pair in an f-plane shallow water system. Bythis simple setting, we can derive analytical estimation forthe far-field of spontaneous gravity wave radiation, using thetheory of the vortex sound (Lighthill theory). In addition, wealso perform numerical simulation of this setting (Fig.2). Weuse a new spectral model in the unbounded domain byprojection from plane to sphere. Then there is no reflectionof radiated gravity waves at the boundary. This model allowsus to estimate gravity wave amplitude with high accuracy.We check both accuracies of the numerical model and theanalytical estimation. The dependencies of parameters, suchas Rossby and Froude numbers, on spontaneous gravitywave radiation will be discussed.

http://web.hc.keio.ac.jp/~nori/title-eg-k.htm

Fig.1 A snapshot of flow field in a shallow water system on arotating sphere.

Fig.2 A snapshot of flow field in an f-plane shallow water system.

Sutherland, Bruce R.Parameterization of Finite-Amplitude InternalWaves in Climate ModelsSutherland, Bruce R.1; Dosser, Hayley V.1; Scinocca, John2

1. Physics, University of Alberta, Edmonton, AB, Canada2. Canadian Centre for Climate Modelling and Analysis,

Victoria, BC, Canada

The diagnoses of internal wave propagation, anelasticgrowth and breaking in the middle atmosphere are assessedin general circulation models through heuristics based uponobservations and the predictions of linear theory. Beforewave breaking occurs, however, internal waves grow tomoderately large amplitude and so the predictions of lineartheory are drawn into question. Weakly nonlinear theoryshows that the dominant weakly nonlinear dynamics aredetermined by interactions between internal waves and themean flow (the `Stokes drift’) that they induce. Fullynonlinear simulations show, as a consequence, that thenonlinearly modulated waves break at lower levels in theatmosphere than predicted by linear theory. These ideas havebeen introduced into an efficient parameterization of gravitywave drag in general circulation models thus giving betterphysical justification for the low tuning of breakingparameters used in climate simulations.

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Swenson, Gary R.Observations of High Frequency AGWs observed inmesospheric airglow, and the implication to theAGW imposed zonal stress and the residualcirculationSwenson, Gary R.1; Gardner, Chester1; Vargas, Fabio1; Liu,Alan2; Lu, Xian3; Li, Zhenhua3

1. Electrical and Computer Engineering, University ofIllinois, Urbana, IL, USA

2. Physical Sciences, Embry Riddle Aeronautical University,Daytona Beach, FL, USA

3. Atmospheric Sciences, University of Illinois, Urbana, IL,USA

An important circulation system described by Houghton(1978), is the residual circulation associated with the stressimposed on the zonal winds by AGWS in the upperstratosphere and mesosphere. Several subsequent studieshave further characterized the residual circulation includingHolton and Zhu (1984) and Zhu et al. (1997, 2001, and2010). The zonal stress from the filtered AGWs for therespective hemisphere (winter and summer) drives the flowfrom the summer to winter polar regions, with a peak nearsolstice, and induces an upwelling in summer anddownwelling in winter. This important circulation systemconstitutes a dynamic coupling between the mesosphere andlower atmosphere which drives composition exchange,including triatomic molecules, some of which aregreenhouse gases. Observations of the climatologies of AGWdirections and momentum fluxes have been made by anumber of imagers at low, mid, and high latitude stations.The directional climatologies of those observations areassembled here to show that the dominant wave fluxes aremeridional, toward the summer pole for low and midlatitude sites. The AGW hot spot, near the Antarctic circle isshown to be exclusively zonal. These results will be presentedalong with a discussion of the implications for the highfrequency AGW effects on the residual circulation.Houghton, J. T., (1978) The stratosphere and mesosphere,Quart. J. R. Met. Soc., 104, 1-29. Holton, J. R. and X. Zhu,(1984) A further study of gravity wave induced drag anddiffusion in the mesosphere, J. Atmos. Sci., 41, 2653-2662.Zhu, X., P. K. Swaminathan, J. H. Yee, D. F. Strobel, and D.Anderson, (1997) A globally balanced two-dimensionalmiddle atmosphere model: Dynamical studies of mesopausemeridional circulation and stratosphere-mesosphereexchange, J. Geophys. Res., 102, 13,095-13,112. Zhu, X, J-HYee, and E. R. Talaat, (2001) Diagnosis of dynamics andenergy balance in the mesosphere and lower thermosphere, J.Atmos. Sci., 58, 2441-2453. Zhu, X., J.-H Yee, W. H. Swartz, E.R. Talaat, and L. Coy, (2010) A spectral parameterization ofdrag, eddy diffusion and wave heating for a three-dimensional flow induced by breaking gravity waves, J.Atmos. Sci., 67, 2520-2536.

Taguchi, MasakazuConnection of the Stratospheric Quasi-BiennialOscillation with El Niño–Southern OscillationTaguchi, Masakazu1

1. Dept of Earth Sciences, Aichi Univ of Education, Kariya,Japan

Using a stratospheric zonal wind data archive ofradiosonde observations at equatorial stations for 1953–2008, this study investigates whether or not signals of thequasi-biennial oscillation (QBO) vary with the El Niño–Southern Oscillation (ENSO) cycle. The signals of the QBOare represented by trajectories in a phase space spanned bytime series of two leading modes of wind variability. Twoproperties of the trajectories, distance from the origin andtime rate of change in argument, which are proxies foramplitude and phase progression rate of the QBO,respectively, are first examined in relation to seasons andQBO phases. The examination confirms known features ofthe QBO including the so-called seasonal locking and moreregular phase propagation for the westerly phase. A furthercomparison of the properties between cold and warm ENSOconditions (La Niña and El Niño, respectively) revealsunprecedented evidence of clear variations of the QBO withENSO: the QBO signals exhibit weaker amplitude and fasterphase propagation for El Niño conditions. Such variationsare also supported by a composite analysis of zonal windanomalies. A preliminary analysis using the ERA40reanalysis data shows that the ENSO-associated QBOmodulation in the zonal wind is largely unexplained by theresolved wave driving. This suggests an important role ofunresolved small-scale waves, such as gravity waves.

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(a,b) Time-height sections of equatorial zonal wind anomaliescomposited with respect to the westerly wind peaks at 50 hPaduring (a) La Niña and (b) El Niño conditions.The panel (c) showsthe composite wind at 50 (solid) and 20 (broken) hPa. Amplitude ofthe composite wind is also denoted in (d). In (c) and (d), thin linesare used for La Niña, and thick for El Niño conditions.

Tsuchiya, ChikaraUniversal frequency spectra of the short periodfluctuationsTsuchiya, Chikara1; Sato, Kaoru1; Nasuno, Tomoe2; Noda,Akira T.2; Satoh, Masaki2, 3

1. Dept. Earth and Planetary Sci., the Univ. of Tokyo, Tokyo,Japan

2. Japan Agency For Marine-Earth Science And Technology,Yokohama, Japan

3. Atmosphere and Ocean Research Institute, the Univ. ofTokyo, Tokyo, Japan

It is known that in the free atmosphere, wavenumber(frequency) spectra have power law (e.g. VanZandt 1982) dueto gravity waves (Smith et al. 1987; Sato and Yamada 1994).This study focuses on the frequency spectra especially at thesurface because of long-term accumulation of short-timeinterval observations. According to Sato and Hirasawa(2007) using hourly surface data over 50 years in theAntarctic, the frequency spectra have a characteristic shapeproportional to different powers of the frequency with atransition frequency of (several days)−1. In order to confirmthe universality of the characteristic spectra, hourly surfacedata, including surface temperature, sea level pressure (SLP),and zonal and meridional winds collected over 45 years at inJapan, were analyzed. Similar spectral shapes are obtainedfor any physical quantities at all stations. The spectral slopesclearly depend on the latitude, particularly for SLP, which islarger at higher latitudes (see the figure). The analysis wasextended using realistic simulation data over a month(Miura et al. 2007; Noda et al. 2010) with a nonhydrostaticgeneral circulation model (NICAM; NonhydrostaticICosahedral Atmospheric Model; Satoh et al. 2008). It isconfirmed that the model spectra accord well with the 138observations in Japan and Syowa Station in the Antarctic.The spectral slopes are largely dependent on the latitude, i.e.,shallow in the low latitudes, and steep in the middle andhigh latitudes for all physical quantities. The latitudinalchange of the spectral slope is severe around 30°, which maybe due to the dynamical transition from nongeostrophy togeostrophy. The longitudinal variations are also observedaccording to geography. The variance is large in the stormtrack region for the pressure, on the continents for thetemperature, and in the rainy regions in the tropics and inthe storm track regions over the oceans for the winds.

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(a) Frequency spectra of the SLP and their shape paramters atWakayama. (b) Spectral slopes in the low and high frequency rangeβL (cross marks) and βH (circles) as a function of the latitude.

Vanderhoff, JulieEffect of time-dependent, spatially varying shear onvertical propagation of internal wave energyVanderhoff, Julie1

1. Brigham Young University, Provo, UT, USA

Significant energy is contained in internal waves andwhen and where that energy is transferred to varying flowsthroughout the atmosphere may define global scalecirculations. Specifically the vertical flux of horizontalmomentum due to these internal waves propagating isdependent on their path through the atmosphere.Interactions with spatially varying large-scale winds can shifttheir propagation direction and expected location of energydissipation significantly. In addition, time-dependent large-scale flows may shift the waves’ location and alter theinternal wave energy spectrum. Using linear ray tracingtheory an analysis of wave refraction of a realistic spectrumof waves is accomplished and conclusions are drawn on theresulting energy spectra and regions of probably energydissipation. Estimates of these time-dependent effects invarying extratropical regions are made and their cumulativeeffect on global circulation patterns is discussed.

Venkat Ratnam, MadineniGravity wave forcing and its effects in entire middleatmosphere: Study under Atmospheric Forcing andResponses (SAFAR), a major NARL campaign(INVITED)Venkat Ratnam, Madineni1

1. Department of Space, National Atmospheric ResearchLaboratory (NARL), Tirupati, India

Study of Atmospheric Forcing and Responses (SAFAR)is a five year (2009–2014) research programme specifically toaddress the responses of the earth’s atmosphere to bothnatural and anthropogenic forcings using a host ofcollocated instruments operational at the NationalAtmospheric Research Laboratory, Gadanki (13.5oN, 79.2oE), India from a unified viewpoint of studying the verticalcoupling between the forcings and responses from surfacelayer to the ionosphere. As a prelude to the main program apilot campaign was conducted at Gadanki during May–November 2008 using collocated observations from the MSTradar, Rayleigh lidar, GPS balloonsonde, and instrumentsmeasuring aerosol, radiation and precipitation, andsupporting satellite data and extended with full pledgedcampaign since January 2009. Present study focuses on studyof the upward traveling waves in the middle atmospherecoupling the lower atmosphere with the upper atmosphere,their manifestation in the mesospheric temperaturestructure and inversion layers, the mesopause heightextending up to 100 km, and the electro-dynamical couplingbetween mesosphere and the ionosphere which causesirregularities in the ionospheric F-region. Main mechanismsfor the generation of gravity waves (GWs) are convection,wind shear (vertical shear of horizontal wind and/orgeostropic adjustment i.e., spontaneous imbalance in jets)and topography over Indian region. During south-westmonsoon season (June-August) over Indian region bothconvection and wind shear co-exists. In order to understandwhich mechanism dominates for generating the GWs fewspecial experiments has been conducted with MST radarunder theme 3 of SAFAR. MST Radar was operatedcontinuously for 72 hours to capture high frequency GWsfollowed by every six hours observations for capturingmedium scale to inertial period waves in different seasons.During this time, radiosonde has been released for every sixhours in addition to the regular (daily once) launchthroughout the season. These two data sets are utilizedeffectively to characterize the jet stream and associated GWs.Although two major sources, that is, strong convection andwind shears coexist during monsoon season, wind shear(both vertical shear of horizontal wind and geostropicadjustment) is found responsible for the generation of GWson various scales. This raises the question, what happened tothe waves generated due to convection? The purpose of thispresentation is not only to share the knowledge that wegained from the SAFAR pilot campaign, but also to informthe international atmospheric science community about theSAFAR program as well as to extend our invitation to join inour study.

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Vincent, Robert A.Gravity Wave Generation by Tropical Convectionand Middle Atmosphere Response (INVITED)Vincent, Robert A.1; Alexander, M. J.2; Kovalam, Sujata1;Dolman, Bronwyn1; MacKinnon, Andrew1; Reid, Iain M.1

1. Physics, University of Adelaide, Adelaide, SA, Australia2. Colorado Research Associates, Boulder, CO, USA

The TWPICE campaign centered on Darwin (12°S,131°E) in northern Australia in January-February 2006provided an opportunity to study gravity wave generation byconvection and the associated wave propagation andmomentum transport. The project used a variety of radars tostudy the spatial and temporal variability of rainfall and theassociated latent heat release during large convective storms.A high-resolution numerical model utilized the latent heatrelease to compute the spatial and geographic variation ofgravity wave generation and propagation into the lowerstratosphere. Gravity wave ray-tracing techniques were thenused to estimate the wave flux penetrating to heights near 90km, where the results were compared with directmeasurements made using a meteor radar. An analysis ofmeteor radar (MR) detection techniques is used to assess thereliability of wave fluxes derived from MR observations. It isshown that, provided the meteor rates are high enough, waveenergies can be reliably measured. This result is used to‘calibrate’ the indirect fluxes from the model, includingmomentum fluxes and the associated wave drag. It is shownthat wave fluxes have a high degree of temporal variability,with consequent variability in momentum flux depositionand wave drag. A number of storm events are studied indetail. Outcomes can be used to help constrain gravity waveparametrization schemes.

Wang, ShuguangGravity Wave Sources in Tropospheric WeatherSystems (INVITED)Wang, Shuguang1; Zhang, Fuqing2

1. Department of Applied Physics and AppliedMathematics, Columbia University, New York, NY, USA

2. Department of Meteorology, The Pennsylvania StateUniversity, State College, PA, USA

Gravity waves are one of the most fundamentaldynamical processes in the atmosphere. They are closelyassociated with a wide variety of atmospheric processesranging from micro-scale to global-scale dynamicalphenomena. A better knowledge of these processes demandsa complete understanding of source mechanisms by whichthey are generated. In this talk, we focus on gravity wavesources within tropospheric weather systems, includingatmospheric convection, upper tropospheric jets and surfacefronts. In particular, we review recent developments in theunderstanding of source mechanisms of gravity wave fromupper tropospheric jets. Two types of idealized atmosphericjets will be discussed: vortex dipole jets and baroclinic jets.Recent studies have demonstrated that wave generation fromquasi-balanced dipole-jets can be considered as forced linear

responses in a linear framework. In this talk, we will presentfurther evidence that gravity waves from a highly transientbaroclinic jet follows similar linear dynamics.

Watanabe, ShingoBrief History of Ultra-High Resolution GlobalModel Studies and Future Plans (INVITED)Watanabe, Shingo1; Hamilton, Kevin2

1. IPCC/JAMSTEC, Yokohama, Japan2. IPRC/University of Hawaii, Honolulu, HI, USA

Besides the development of high-resolution globalnumerical weather prediction (NWP) models, e.g. at ECMWF,free-running high-resolution general circulation models(GCMs) have been used to study dynamics of the middleatmosphere (MA). The GFDL SKYHI GCM has the longesthistory of this research area. It was the first high-top (~80 km)GCM with 40 vertical layers without gravity wave (GW)parameterization. The horizontal resolution (HR) hasincreased with time; N30 (1980), N90 (1986), N150 (1997),and N270 (1999). (The number following N means model’sgrid points between the equator and pole.) One of the mostimportant outcomes was that reality of the MA simulationscontinuously improved with increasing HR, as resolvedspectra of GWs increased. A cold pole bias within the australwinter polar vortex was about -70 K and -35 K in N30L40 andN90L40, while it was nearly eliminated in N270L40(Hamilton et al., 1995 and 1999). The N270L40 alsosimulated realistic GW horizontal-wavenumber (k-) spectra(Koshyk et al., 1999). The MACCM2 at NCAR also obtainedsimilar results to SKYHI that HR of T106 (~N80) wasinsufficient to eliminate the cold pole bias in the polar vortex(Boville, 1997). It was the late 1990’s during which severaltypes of non-orographic GW parameterizations weredeveloped, and were generally implemented to lower-HR high-top GCMs (e.g., McLandress, 1998). In Japan, the University ofTokyo (CCSR) group cooperated with NIES has developedhigh vertical resolution (VR) GCMs. The T21L60 GCM with~500 m VR firstly succeeded to simulate the equatorial quasi-biennial oscillation (Takahashi, 1996). Pioneered by T106L53aqua planet GCM of Sato et al. (1999), this Japanese groupintensively studied gravity waves in ~50 km-top T106 GCMswith high VR (500-600 m) (e.g., Kawatani et al. 2003). Afterthe appearance of the Earth Simulator in 2002, a high-top (85km) and high VR (300 m) T213L256 GCM was developed forthe KANTO project to study GWs and their roles in MA (seeKawatani et al. 2010 and references therein), as well as theextratropical tropopause region (Miyazaki et al. 2010). The150 km-top T213L270 JAGUAR was also developed combiningthe KANTO GCM and the Kyushu-GCM, and used to studyinteractions between tides and GWs (Watanabe and Miyahara,2009). The Japanese modeling group (CCSR/NIES/JAMSTEC/ Kyushu Univ.) is currently planning modelingactivity in next 5 years in conjunction with operations of theAntarctic PANSY radar. They would increase HR of JAGUARto T639 that would likely bridge hydrostatic GCMs and anon-hydrostatic global cloud resolving model, i.e., verticalextension of 7 km-NICAM is also planned. However, there

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could be several options other than using the free-runningJAGUAR to study GWs appearing in near real-timeobservations. For detailed generation and propagation ofGWs, it would be more straightforward to use finer-resolutionmesoscale models being nested onto high-top NWP modelsthat assimilate observations (e.g. ECMWF and NOGAPS-ALPHA). There are also issues in the dissipation due tosub-grid processes and secondary generation of GWs near themesopause, which cannot be represented by hydrostaticGCMs. We would like to openly discuss about these issues inthis conference.

Wei, JunhongAircraft Measurements And Numerical SimulationsOf Gravity Waves In The Extratropical UTLS RegionDuring The START08 Field CampaignWei, Junhong1; Zhang, Fuqing1; Zhang, Meng1; Bowman,Kenneth2; Pan, Laura3; Atlas, Elliot4

1. Department of Meteorology, Pennsylvania StateUniversity, State College, PA, USA

2. Department of Atmospheric Sciences, Texas A&MUniversity, College Station, TX, USA

3. National Center for Atmospheric Research, Boulder, CO,USA

4. Rosenstiel School of Marine and Atmospheric Science,The University of Miami, Miami, FL, USA

Gravity waves are one of the key dynamical processescontributing to the structure and composition of theextratropical upper-tropospheric and lower-stratospheric(UTLS) region. Previous field campaign mainly focuses onterrain-induced gravity wave, but the generation andmaintenance of mesoscale gravity waves in a jet-front systemis still not clear. One of the primary objectives of theSTART08 (Stratosphere-Troposphere Analyses of RegionalTransport Experiment 2008) field experiment is tocharacterize the source and impact of these waves with thecomparison between high-resolution aircraft measurementsand mesoscale models. Preliminary analyses have beenconducted to examine the GV aircraft flight-levelobservations to extract gravity wave information and toexplore the spectral distributions of different variables in thelower stratosphere during the START08 mission. One of theresearch mission flights, RF02, was dedicated for the firsttime to probing mesoscale gravity waves associated withstrong upper-tropospheric jet-front systems. It is shown byspectral analysis that clear signals of significant waves withwavelengths ranging from 10 to 300 km present in almostevery leg of the 8-hour flight sampled by the aircraft, mostlyin the lower stratosphere. Strong localized variations of thewave signals can be observed with wavelet analysis, over thearea of background flow conditions covered by near-jet core,jet over the high mountains and the exit region of the jet. Inorder to testify the physical reliability of such localized wavesignals, the phase and amplitude relation of linear theory isstudied based on wavelet-filtered observational data. Themesoscale component of the gravity waves measured hassome qualitative similarity to those predicted by a real-time

mesoscale forecast model with horizontal grid spacing of 15km and a cloud-resolving hindcast simulation. However, oneof the most noticeable disagreements between simulationand observation lies in the small-scale component of verticalvelocity. We will continue to examine how well the currentgeneration of mesoscale models predicts the excitation andcharacteristics of the gravity waves, how they contribute tounderstanding the dynamics and impacts of these waves inthe UTLS region, how surface fronts and moist convectionimpact upper-level gravity waves during the life cycle ofbaroclinic waves, and the reliability of aircraft measurementand high-resolution numerical simulations.

http://www.met.psu.edu/people/jzw158

Williams, Bifford P.Observations of Large Vertical Winds Associatedwith Short Period Gravity Waves in the WinterPolar Mesopause RegionWilliams, Bifford P.1; Fritts, David C.1

1. Colorado Research Associates, NorthWest ResearchAssociates, Boulder, CO, USA

The sodium wind-temperature lidar at the ALOMARobservatory (69N,16E) can measure the sodium density from85-100km altitude with 150 m height and 15 sec timeresolution during winter under good conditions. Radialwinds and temperatures can be measured with 1-2 m/s and1-2 K error after averaging to 1 min in time and 1-2 km inaltitude. This allows determination of the short period wavespectrum down to 30sec in Na density and 2min in wind andtemperature. Preliminary analysis shows a number of shortperiod oscillations with large vertical wind amplitudes of upto 25m/s in extreme cases with corresponding verticalmotion of the Na layer and adiabatic temperatureperturbations. We will present the properties of these wavesand compare with gravity wave theory for waves near thebuoyancy period.

Williams, Paul D.Gravity Waves in the Laboratory: Mechanisms,Properties, and ImpactsWilliams, Paul D.1

1. Department of Meteorology, University of Reading, UK,Reading, United Kingdom

I will describe a series of laboratory experiments inwhich gravity waves are generated ubiquitously. Theapparatus employed is the rotating annulus, which has beenused for decades to study large-scale mid-latitudeatmospheric flows. I will discuss the following aspects of thegravity waves: their generation mechanisms; their properties;and their impacts on the large-scale flow. The evidencesuggests that the gravity waves are generated asspontaneous-adjustment emission through loss of balancein the large-scale flow. Therefore, these experiments provideperhaps the first direct experimental evidence that allevolving balanced flows will tend to emit gravity waves, inaccordance with theoretical expectations. The experiments

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imply an inevitable emission of gravity waves at Rossbynumbers similar to those of the large-scale atmospheric andoceanic flow. The amplitude of the emitted gravity wavesvaries linearly with Rossby number, at constant Burgernumber (or rotational Froude number). This linear scalingchallenges the notion, suggested by several dynamicaltheories, that gravity waves generated by balanced motionwill be exponentially small. It is estimated that the balancedflow leaks roughly 1% of its energy each rotation period intothe gravity waves, at the peak of their generation. The impactof the gravity waves on the large-scale flow is generally small.However, there are circumstances in which the gravity wavestrigger rapid regime transitions between different large-scaleflow patterns. Motivated by this finding, it has recently beensuggested that stratospheric polar vortex splits may inprinciple be triggered by gravity-wave noise.

http://www.met.reading.ac.uk/~williams/

The view of the rotating annulus from above, showing trains ofgravity waves in the troughs of the large-scale flow pattern. A colormovie showing the evolving flow can be viewed athttp://www.youtube.com/RotatingAnnulus .

Wright, CorwinHIRDLS gravity wave validation and case studiesWright, Corwin1; Gille, John1, 2

1. Atmospheric Chemistry Division, National Center forAtmospheric Research, Boulder, CO, USA

2. Center for Limb Atmospheric Sounding, University ofColorado, Boulder, CO, USA

The HIRDLS instrument on NASA’s Aura satelliteprovides temperature soundings across the globe, with ahigh vertical resolution and narrow along-track profilespacing which greatly facilitates the detection of gravity wavesignals in the stratosphere. In this poster, we will firstly showcomparisons of the gravity wave detection capabilities ofHIRDLS with SABER and COSMIC, and then show twocases studies of the use of HIRDLS data to analyse gravitywave results, one considering the dynamics of the Arcticstratosphere during Arctic winter 2006 (previously publishedas Wright et al (2010)) and the other considering gravitywaves produced by the Indian, African and Americanmonsoons.

Wu, Dong L.Gravity waves and cloud structures: AIRSobservationsWu, Dong L.1; Gong, Jie1

1. M/S 169-237, Jet Propulsion Laboratory, Pasadena, CA,USA

Interactions between wave dynamics and humidity formclouds at wide spatial scales. On one hand, waveperturbations can enhance cirrus formation in the uppertroposphere, regulating cloud and water vapor distributionsand feedbacks on climate. On the other hand, energyexchanges and perturbations from organized cloud systemsact as a source of new wave generation, which may affectgeneral circulation in the middle and upper atmosphere. Inthis study we analyze organized cloud structures using AIRSradiances from the 90 view angles, each of which has abeamwidth of ~13 km, to characterize how clouds aremodulated by gravity waves. We focus on five tropicalconvective regions and compiled eight-year (2003 - 2010)statistics of cloud-induced radiances. The ensemble of AIRScloud radiances suggests that more or stronger anvil cloudsare observed near the local noon (13:30 LST) from east viewangles of the AIRS scans, whereas the cloud amounts fromeast and west views are roughly equal at midnight (01:30LST). Oblique view angles are generally more sensitive toanvil clouds than the nadir views. However, the sensitivity isreversed for deep convective clouds. The east-view preferenceof AIRS cloud radiances is slightly larger over lands thanover oceans, which can be explained by gravity-wave-inducedstructures embedded in anvil clouds. The wave-inducedbands appear to be closely associated with the uppertroposphere wind shear at noon when convection isinitiated, but it may not be the case at midnight whenconvection is at its mature or decay stage. These results haveimportant implications for gravity wave spectra launchedfrom the clouds in the upper troposphere, which will affectwave momentum budgets in the middle and upperatmosphere.

Xue, XianghuiQBO generated in WACCM using inertial gravitywavesXue, Xianghui1; Liu, Hanli2

1. School of Earth and Space Sciences, Univ. of Sci.& Tech.of China, Hefei, Anhui, China

2. NCAR/HAO, Boulder, CO, USA

In this work we generalize the gravity waveparameterization scheme currently used in WACCM, whichis based upon Lindzen’s linear saturation theory, to includea spectrum of inertial gravity waves with horizontalwavelength at 1000 km. In WACCM simulations with thenew gravity wave parameterization and the standardWACCM horizontal and vertical resolutions, thestratospheric zonal winds exhibit a strong oscillation aroundthe equator with downward propagation of the windreversals. The period of the oscillation is dependent on the

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strength of the gravity wave forcing. Therefore, quasi-biennial oscillation can be internally generated with theproper selection of drag efficiency of the gravity waves. Theoscillation thus generated are compared with observed QBO.These experiments demonstrate the need to parameterizeinertial gravity waves for generating QBO in GeneralCirculation Models (GCMs).

Yamashita, ChihokoGravity Wave Variations during the 2009Stratospheric Sudden WarmingYamashita, Chihoko1, 2; Liu, Han-Li1; Chu, Xinzhao2

1. HAO / NCAR, Boulder, CO, USA2. CIRES and University of Colorado, Boulder, CO, USA

Gravity waves are one of the key elements for driving theatmospheric coupling from the stratosphere to thethermosphere during stratospheric sudden warmings(SSWs). The limited knowledge of gravity wave variationsand their source distribution leads to the uncertainty in theSSW simulations by general circulation models. In thisstudy, ECMWF-T799 (0.25° horizontal resolution and 91vertical levels up to 0.01 hPa) is used to study gravity wavevariations and their source variations during the 2009 SSW.Resolved gravity waves in ECMWF-T799 are validated withCOSMIC/GPS and lidar observations in the polar regions.ECMWF results show that overall gravity wave strengthincrease prior to the 2009 SSW. The magnitude andoccurrence of gravity waves correlate well with the locationand strength of the polar vortex that is strongly distorted byplanetary wave growth. During the development and onsetof SSW, the zonal-mean gravity wave potential energydensity (GW-Ep) increases on January 5 and 15-22 inassociation with the growth of planetary wave wavenumber 1and wavenumber 2, respectively. The altitude where PWsreach maximum amplitude is initially in the lowermesosphere, and then progress downward. GW-Epenhancement also seems to show a corresponding descentfrom January 5-22. GW-Ep peaks before the wind reversaland significantly weakens after the SSW. These variations areconfirmed by COSMIC/GPS observations. To betterunderstand the gravity wave variations, both statistical studyand case study of gravity wave source variations will bepresented.

Yigit, ErdalDynamical and Thermal Effects of Gravity Waves inthe terrestrial Thermosphere-IonosphereYigit, Erdal1; Medvedev, Alexander S.2; Ridley, Aaron J.1

1. Atmospheric, Oceanic and Space Sciences, University ofMichigan, Ann Arbor, MI, USA

2. Max Planck Institute for Slar System Research,Katlenburg-Lindau, Germany

It is well established that small-scale internal gravitywaves (GWs) play an important role in the dynamics of themiddle atmosphere. Their contributions to the momentumbudget of the mesosphere and the lower thermosphere, i.e.,

up to the turbopause, have been investigated extensively.Historically, their propagation above the turbopause and theresulting effects could not be studied due primarily to thelack of an appropriate GW parameterization for the wholeatmosphere system. Recently, we have developed a newspectral nonlinear GW parameterization that accounts forthe penetration of GWs of lower atmospheric origin into theupper atmosphere, and quantifies the resulting dynamicaland thermal effects from wave damping [1]. In addition tononlinear wave-wave interactions and self-interactions, wavedissipative mechanisms such as ion drag, molecular viscosityand conduction, eddy viscosity, and radiative damping areadditionally accounted for. Our results based on generalcirculation modeling [2-4] suggest that GWs penetratesignificantly into the upper atmosphere up to F2 layeraltitudes, and the associated momentum deposition andneutral gas heating rates are comparable to ion drag andJoule heating, respectively, at those heights. We demonstratethat proper accounting for GW dissipation above theturbopause improves model simulation with respect to twowidely used empirical models of the upper atmosphere. Anoverarching implication of our results is that small-scaleGWs must be considered in the observational and modelingstudies of the thermosphere-ionosphere system similar tothe mesosphere and lower thermosphere. 1. Yigit, E., A. D.Aylward, A.S. Medvedev (2008), J. Geophys. Res., 113,D19106,doi:10.1029/2008JD010135. 2. Yigit, E., and A. S.Medvedev (2010), J. Geophys. Res., 115, A00G02,doi:10.1029/2009JA015106. 3. Yigit, E., and A. S. Medvedev(2009), Geophys. Res. Lett., 36, L14807,doi:10.1029/2009GL038507. 4. Yigit, E., A. S. Medvedev, A.D. Aylward, P. Hartogh, and M. J. Harris (2009), J. Geophys.Res., 114, D07101, doi:10.1029/2008JD011132.

Yue, JiaConcentric gravity waves generated by deepconvections in the Great Plain and observed by all-sky airglow imager in the mesopauseYue, Jia1; Vadas, Sharon2; Nakamura, Takuji3; She, Chiao-Yao4; Lyons, Walter5; Liu, Han-Li1

1. High Altitude Observatory, National Center forAtmospheric Research, Boulder, CO, USA

2. NorthWest Research Associates, Boulder, CO, USA3. National Institute for Polar Research, Tokyo, Japan4. Physics, Colorado State University, Fort Collins, CO, USA5. FMA, Fort Collins, CO, USA

Expanding concentric rings of gravity waves wereobserved on 9 nights near equinoxes by the all-sky OHimager at Yucca Ridge Field Station (40.7N, 104.9W) nearFort Collins, Colorado. The pattern on 11 May 2004 wasobserved for about 1.5 hours, with the rings encompassingnearly 360 for the first 30 minutes. The centers of the ringswere observed at the geographic locations of two convectiveplumes. We measure the horizontal wavelengths and periodsof these gravity waves as functions of both radius andobservation time. The observations compare favorably withpredictions using the internal gravity wave dispersion

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relation with assumed zero wind. Furthermore, the event on8 September 2005 lasted 5 hours and one-on-one correlationbetween the tropospheric wave source and thecorresponding mesospheric gravity waves is evident. Since 9out of the 10 events of concentric patterns among 760nights of image were observed in May or late August/earlySeptember, we hypothesize that the weak mean backgroundzonal wind near equinoxes is a necessary condition forgravity waves excited from convective overshoots near thetropopause to be observed as concentric rings in the OHlayer. Ray tracing program results with the background windand parameterized plumes will be compared to theobservations.

Concentric gravity waves on 8 September 2005 projected on the 800km^2 geographic coordinate. The centers of the waves are markedby red dots.

Zagar, NedjeljkaLagre-Scale Equatorial Waves in the MiddleAtmosphere Based on Multiyear ECMWF analysesZagar, Nedjeljka1

1. University of Ljubljana, Ljubljana, Slovenia

Three-dimensional global normal-mode functionexpansion is applied to operational analysis of ECMWFwhich extend up to 80 km height (1 Pa). The normal-modeexpansion allows to quantify energy in balanced and inertio-gravity motions, various horizontal scales and verticalstructures. The diagnosis is concentrated on most energeticwaves in the middle atmosphere in the tropics and theirspatio-temporal characteristics. The vertical wavepropagation is diagnosed in the space of normal modesbased on 91-model level analysis fields for the last 4 years.

Zhang, FuqingCoupling between gravity waves and tropicalconvection at mesoscalesLane, Todd P.1; Zhang, Fuqing2

1. The University of Melbourne, Melbourne, VIC, Australia2. The Pennsylvania State University, University Park, PA,

USA

In this study, an idealized cloud-system resolving modelsimulation and linear theory are used to explore thecoupling between a tropical cloud population and themesoscale gravity waves it generates. Spectral analyses of thecloud and gravity wave fields identify a clear signal ofcoupling between the clouds and a deep tropospheric gravitywave mode with a vertical wavelength that matches thedepth of the convection, which is about 2/3 the troposphericdepth. This vertical wavelength and the period of the waves,defined by the characteristic convective timescale, meansthat the horizontal wavelength is constrained through thedispersion relation. Indeed, the wave-convection couplingmanifests at the appropriate wavelength, with the emergenceof quasi-regular spacing of order 100 km. It is shown thatclouds at this spacing achieve a resonant state, at least for afew convective lifecycles. Such regular spacing is a keycomponent of cloud organization and is likely a contributorto the processes controlling the upscale growth of convectivesystems. Other gravity wave processes are also elucidated,including their apparent role in the maintenance ofconvective systems by providing the mechanism for renewedconvective activity and system longevity.

Zhang, FuqingDynamics and Impacts of Gravity Waves in theBaroclinic Jet-Front Systems with Moist Convection(INVITED)Zhang, Fuqing1; Wei, Junhong1

1. Penn State University, University Park, PA, USA

This study explores the dynamics and impacts of thegravity waves generated by the tropospheric baroclinic jet-front systems with moist convection. We performedhigh-resolution convective-resolving simulations of idealizedmoist baroclinic waves with multiply-nested mesoscalemodels initialize with a balanced unstable baroclinic jet in amesoscale model with modest convective instability. Withthe inclusion of moist convection, the backgroundbaroclinic wave intensifies faster and stronger, resulting instronger and higher-frequency gravity waves in the jet-exit-region through balanced adjustment as in the drysimulations. Moreover, there are even smaller-scale (<100km)large-amplitude gravity waves apparently generated fromand/or coupled with individual convective cells andassociated vigorous diabatic heating within the moistbaroclinic waves. Given most strong midaltitude baroclinicwaves are often associated with strong convection, thechanges in gravity wave characteristics and intensity in themoist environment can have profound impacts on the the

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momentum and energy fluxes by these waves, andsubsequently their influence on the general circulation.

http://www.met.psu.edu/people/fuz4

Zülicke, ChristophResponse of the mesosphere to stratosphericwarmingsZülicke, Christoph1; Becker, Erich1

1. Theory and Modelling, Leibniz Institute of AtmosphericPhysics, Kühlungsborn, Germany

The appearance of mesospheric coolings and windreversals during sudden stratospheric warmings is studied asan example of vertical coupling in the middle atmosphere.The data are simulations of the Kühlungsborn MechanisticCirculation Model. First the statistics of such events iscompared with the indices proposed Charlton & Polvani(2007). As well the frequency as well as the intensity appearto be realistic. Second, the relation of stratosphericwarmings to mesospheric coolings is studied. These appearcorrelated in 92 % of the variance as is shown with a speciallydeveloped coherency index. The third phenomenon, thecorrelation of wind reversals in the stratosphere and themesosphere, is not as clear – 75 % of the variance appears tobe coherent, while 25 % are anticoherent. This behavior isconsistent with the thermal wind equation as has beenproven. The question for cause and reason for differentstructures of the mass and flow field is discussed.

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