stratospheric and mesospheric applications of sciamachy limb observations c. von savigny, a....
TRANSCRIPT
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Stratospheric and Mesospheric Applications of SCIAMACHY Limb Observations C. von Savigny, A. Rozanov, G. Rohen, K.-U. Eichmann, E. J. Llewellyn*, J. W. Kaiser+, M. Sinnhuber, M. Scharringhausen, P. Ulasi, H. Bovensmann, and J. P. Burrows
Institute of Environmental Physics/Remote Sensing, University of Bremen, Bremen, Germany* Department of Physics and Physics Engineering, University of Saskatchewan, Saskatoon, Canada+ Remote Sensing Laboratories, University of Zurich, Zurich, Switzerland5th German SCIAMACHY Validation Team Meeting
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Outline
Stratospheric applicationsPolar stratospheric cloudsMinor constituent profiles
Mesospheric applicationsMesospheric ozone profilesOH* (3-1) rotational temperature retrievalsNoctilucent clouds
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SCIAMACHY Limb GeometryTangent height range: 0 to 100 km
Tangent height step size: 3.3 km
Vertical FOV: 2.6 km
Observation optimised for limb-nadir matching
Duration of Limb sequence: 60 s
Observed is limb scattered solar radiation and terrestrial airglow emissions
On the Earths night side limb emissions are observed in a dedicated mesosphere / thermosphere observation mode with tangent height between 75 and 150 km.
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Polar Stratospheric Clouds
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Step I: Determine colour index profiles
Step II: Determine vertical gradient of CI(TH):
with TH = 3.3 km
Theoretical maximum (TH) values for 15-30 km altitude range:
a) 1.05 for pure Rayleigh atmosphere b) 1.1 for stratospheric background aerosol c) 1.16 for moderate volcanic aerosol d) 1.55 for extreme volcanic aerosol
Detection threshold chosen: (TH) = 1.3
detection is somewhat biased towards optically thicker PSCsPSC detection with limb measurements
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Maps of detected PSCs (open circles: detected PSCs) superimposed to UKMO temperature field at 550 K potential temperature (about 22 km) for August 7-12, 2003. PSC maps
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Temporal variation of PSC altitudesPSC descent rates for 2003:
Santacesaria et al. [2001] : 2.5 km / monthat 66 S / 140 E based on a 9-year Lidar climatologyFromm et al. [1997] :2.0 km / month derived from POAM II
50 S - 60 S 2.5 km / month60 S - 70 S 2.0 km / month70 S - 80 S 1.2 km / month
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Histograms of temperature at PSC altitude
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Stratospheric Minor Constituents
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The scia-arc website The scia-arc website provides value-added scientific data products
Presently available limb data products: stratospheric profiles of O3, NO2 and BrO
In preparation: - mesospheric O3 profiles - maps of NLCs and PSCs - OH rotational temperatures at the mesopausehttp://www.iup.physik.uni-bremen.de/scia-arc
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One week before the major stratospheric warming: September 12, 2002Savigny et al. [2004]
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The ozone hole split: September 27, 2002
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At mid-latitudes typical BrO mixing ratios are about 10 pptv, corresponding to about 50 % of the available inorganic bromine (20 pptv). The rest is almost exclusively BrONO2 .[e.g., Sinnhuber et al., 2002] Within the vortex BrO mixing ratios are most likely enhanced due to the reduced NO2, therefore reduced formation of BrONO2.
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OH rotational temperature retrievals
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OH* produced and vibrationally-rotationally excited at mesopause altitudes by: H + O3 OH* (v 9) + O2 + 3.3 eVAirglow emission centered around 87 km with about 8 km FWHM
Relative population of rotational levels governed by Boltzmanns distributionMeasurements of relative intensities of rotational emission lines makes retrieval of OH rotational temperature possible
OH*(v = 3) is in local thermodynamical equilibrium (LTE) for lower rotational quantum numbers because:- collisional frequency at 86 km is 3 104 s-1- lifetime of OH at v = 3 is about 0.014 s rotational temperatures are equal to kinetic temperature of ambient air
Retrieval of OH* (3-1) rotational temperatures
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EJ J(J+1)J=0J=2J=3J=4J=5Selection rule: J = 0,+1,-1=3=1J=1J=0J=2J=3J=4J=5J=1Q-branchP-branch
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Impact of different Einstein coefficients used:Kovacs [1969], Mies [1974], Goldman et al. [1998]TKovacs TMies = 1.1 K and TKovacs TGoldman = 3.2 KSample OH spectral fitIterative retrieval approach:
linear fit with 2nd order polynomial
(2) non-linear fit (Levenberg-Marquard) driving OH model, including -shift
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CalibrationmeasurementsCalibrationmeasurementsLimbmeasurementsLimbmeasurementsCalibrationmeasurementsCoverage of Limb eclipse measurements
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Replacement of nighttime Nadir observations by limb observations
Implemented on September 6, 2004SCIAMACHY Operations Change Request 19
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GRound-based Infrared P-branch Spectrometer (GRIPS) I at Hohenpeissenberg (47 N / 11 E)
GRIPS-I data provided by Michael Bittner and Kathrin Hppner (DLR)First validation results Mesospheric Temperature Mapper (MTM) at Hawaii (21 N / 204 E)
MTM data provided by Mike Taylor and Yucheng Zhao (Utah State University)
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OH-Temperatures 2003 Temperatures: for latitudes from 20 to 70 deg from July 2002 up to now.
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Mesospheric Ozone
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Weighting functionsAveraging kernels
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Ozone depletion during the Oct. / Nov. 2003 SPEsHOx production by ionization:
O2+ + O2 + M O2+O2 + MO2+O2 + H2O O2+H2O + O2 O2+H2O + H2O H3O+OH + O2H3O+OH + H2O H3O+ H2O + OHH3O+ H2O + e- 2 H2O + HO2+ + H2O + e- O2 + H + OH(Courtesy M.-B. Kallenrode and M. Sinnhuber )NOx is formed as well
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Ozone depletion during the Oct. / Nov. 2003 SPEsOzone loss at 55 km and north of magnetic 60 N relative to October 20 24 reference period 40 MeV protons penetrate the atmosphere Down to about 45 km altitude
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Observations vs. ModelSCIAMACHYmeasurementsModel simulations(M. Sinnhuber)Percent ozone loss north of 60 N magnetic latitudeReference period:October 20 24, 2003
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Noctilucent Clouds
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UV limb radiance profileswith NLCs and without NLCs
Detection of Noctilucent Clouds (NLCs)
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I. In single scattering approximation the PMC backscatter is given by:q(,): Differential scattering cross sectionS(): Solar irradiance spectrumII. The sun-normalized PMC backscatter spectrum:with spectral exponent NLC particle size determination I
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Ambiguity: spectral exponent does not monotonically increase with increasing radius
Use several and significantly different wavelengths to determine r and [von Cossart et al, 1999].Assumptions:
Mie theory, i.e., homogeneous dielectric spheres
Refractive index of ice [Warren, 1984]
Log-normal distribution The spectral exponent is related to the PMC particle sizes by Mie-calculationsSimulated spectral exponents for log-normal distribution with = 1.4 NLC particle size determination II
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NLC particle size determination January 2003
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ConclusionsSCIAMACHY limb observations with their broad spectral coverage and extended altitude range both on the day and nightside allows a wide range of stratospheric and mesospheric to be studied:
Optically thin aerosols like NLCs and PSCs
Minor constituent profiles (O3, NO2, BrO; soon H2O, CH4)
Mesopause temperature (soon Rayeigh temperatures)