Major discrepancies in the Major discrepancies in the analyzed representation of analyzed representation of prominent features of the prominent features of the

tropical atmospheretropical atmosphere

Oreste RealeOreste Reale

GEST/UMBCGEST/UMBC

andand

NASA Goddard Laboratory for AtmospheresNASA Goddard Laboratory for Atmospheres

OutlineOutline

AEJ representation in state-of-the-art AEJ representation in state-of-the-art reanalysesreanalyses AEJ representation on weather-time-scales in AEJ representation on weather-time-scales in operational operational

analysesanalyses during SOP-3 NAMMA during SOP-3 NAMMA (2006)(2006) Vertical soundings during SOP-3 NAMMA Vertical soundings during SOP-3 NAMMA (2006)(2006) Mis-representation of Tropical cyclones’ analyses away Mis-representation of Tropical cyclones’ analyses away

from HH flights (Atlantic) in from HH flights (Atlantic) in operational analyses operational analyses (2006)(2006) Absence of TC Nargis (Indian Ocean,Absence of TC Nargis (Indian Ocean, 2008 2008) from analyses) from analyses Mid-tropospheric flow over the entire tropical Pacific in Mid-tropospheric flow over the entire tropical Pacific in

August 2010August 2010 in in NCEP operational, ECMWF operational, NCEP operational, ECMWF operational, andand MERRA MERRA

ConclusionsConclusions

AEJ representation in AEJ representation in state-of-the-art reanalysesstate-of-the-art reanalyses

Previously published work (Wu et al., 2009) shows Previously published work (Wu et al., 2009) shows substantial differencessubstantial differences between reanalyses in the between reanalyses in the monthly meanmonthly mean representation of the representation of the African African Easterly Jet (AEJ)Easterly Jet (AEJ)

ERA-40, NCEP-R2, JRA-25 provide very different ERA-40, NCEP-R2, JRA-25 provide very different descriptions of the AEJ structure, and of the descriptions of the AEJ structure, and of the horizontal shearhorizontal shear in the in the cyclonically-sheared portion cyclonically-sheared portion of the AEJ of the AEJ

M.-L. C. Wu, Reale, O., S. Schubert, M. Suarez, M.-L. C. Wu, Reale, O., S. Schubert, M. Suarez, R. Koster, P. Pegion, 2009: R. Koster, P. Pegion, 2009:

African Easterly Jet: Structure and Maintenance. African Easterly Jet: Structure and Maintenance. J. Climate, J. Climate, 22,22, 4459-4480. 4459-4480.

From From Wu et al. (2009)Wu et al. (2009)

Fig 2Fig 2

July zonal windJuly zonal wind (m s−1, contours every 1 m s−1, 0 omitted, solid: positive, (m s−1, contours every 1 m s−1, 0 omitted, solid: positive, dashed: negative) climatology dashed: negative) climatology (1980–2001)(1980–2001) based on (top to bottom) based on (top to bottom) ERA-40, NCEP R2, ERA-40, NCEP R2, and JRA-25and JRA-25 data: (left) meridional horizontal shear of the zonal wind at 600 hPa data: (left) meridional horizontal shear of the zonal wind at 600 hPa and (right) meridional cross section at 0° longitude. (Wu et al., 2009, and (right) meridional cross section at 0° longitude. (Wu et al., 2009, J.Climate)J.Climate)

Large differencesLarge differences in inAEJ AEJ SHAPESHAPE,, INTENSITY INTENSITYVERTICAL STRUCTUREVERTICAL STRUCTUREand and distribution of thedistribution of thehorizontal shearhorizontal shearin a in a 22-year average22-year averageperformed on performed on ERA-40,ERA-40,NCEP-R2,NCEP-R2, and and JRA-25JRA-25. .

AEJ and its instability properties in AEJ and its instability properties in state-of-the-art reanalysesstate-of-the-art reanalyses

Work submitted in Work submitted in 20102010 (Wu et al., 2010) shows (Wu et al., 2010) shows differencesdifferences in the representation of the in the representation of the African Easterly Jet (AEJ)African Easterly Jet (AEJ) seasonalseasonal instability propertiesinstability properties between reanalyses across a between reanalyses across a 22-year average22-year average

Despite revealing some instability property of the AEJ that Despite revealing some instability property of the AEJ that appear data-independent, ERA-40, NCEP-R2, JRA-25 and appear data-independent, ERA-40, NCEP-R2, JRA-25 and MERRA provide very different descriptions of the AEJ MERRA provide very different descriptions of the AEJ horizontal structure, intensity, and of some properties that horizontal structure, intensity, and of some properties that control wave instability on a control wave instability on a seasonal scale (JAS)seasonal scale (JAS)..

M.-L. C. Wu, Reale, O., S. Schubert, M.-L. C. Wu, Reale, O., S. Schubert, M. Suarez, C. Thorncroft, 2010: M. Suarez, C. Thorncroft, 2010:

African Easterly Jet: barotropic instability, waves and African Easterly Jet: barotropic instability, waves and cyclogenesis.cyclogenesis.

Submitted to: J. Climate.Submitted to: J. Climate.

From From Wu et al. (2010)Wu et al. (2010)

Fig 2Fig 2

The analyses differ in terms ofThe analyses differ in terms ofstrengthstrength and and intensity intensity of the low-levelof the low-level

monsoonal flowmonsoonal flow, , slopeslope of the of the barotropically unstablebarotropically unstable part of the part of theAEJ, AEJ, horizontal shear distributionhorizontal shear distribution. .

All Figures show a All Figures show a 22-year JAS average22-year JAS average

Unexpected discrepancies between snapshots of Unexpected discrepancies between snapshots of analyzed representation of the African Monsoon-analyzed representation of the African Monsoon-

Eastern Tropical Atlantic regionsEastern Tropical Atlantic regions

TheThe African Easterly Jet African Easterly Jet at about 600hPa,at about 600hPa, thethe low- low-level monsoonal flow level monsoonal flow (predominantly southwesterly (predominantly southwesterly between 1000 and 800 hPa)between 1000 and 800 hPa) and theand the Tropical Easterly Tropical Easterly Jet Jet (between 200 and 100 hPa)(between 200 and 100 hPa) are theare the critical players critical players inin Atlantic tropical development. Atlantic tropical development.

Comparison between operational NCEP analyses and Comparison between operational NCEP analyses and GEOS-5-produced analyses reveal GEOS-5-produced analyses reveal serious serious discrepanciesdiscrepancies

Validation agains the only vertical sounding in the area Validation agains the only vertical sounding in the area at Cape Verde (15N, 23.5W) during the 2006 NAMMA at Cape Verde (15N, 23.5W) during the 2006 NAMMA campaign,campaign, show that both analyses have large errors show that both analyses have large errors

Huge discrepancies between Huge discrepancies between GEOS-5 and NCEP operational analysesGEOS-5 and NCEP operational analyses

Wind at 5-15N, Wind at 5-15N, 500-600 hPa, has500-600 hPa, hasopposite opposite direction!direction!

Only in the tropicsOnly in the tropicsthe two analysesthe two analysesdiffer substantiallydiffer substantially

Section at 23.5WSection at 23.5W

Largest differences between reanalyses are in the tropics, Largest differences between reanalyses are in the tropics, at about 15N (at about 15N (on the order of 12m/son the order of 12m/s))

larger even thanlarger even thandiscrepancies in the southern hemisphere jet streamdiscrepancies in the southern hemisphere jet stream

NCEPNCEP

GEOS-5GEOS-5

Huge differences in the entire tropical zonal flow Huge differences in the entire tropical zonal flow from 20S to 20N at all levels from 20S to 20N at all levels

Largest Largest mid-troposphericmid-tropospheric wind difference is in wind difference is in the tropics, at 0-10Nthe tropics, at 0-10N

GEOS-5 analysesGEOS-5 analysesproduce a produce a weakerweaker easterly floweasterly flowthan NCEPthan NCEP

GEOS-5GEOS-5

NCEPNCEP

Largest Largest low-tropospheric low-tropospheric wind difference is in wind difference is in the tropics, between 10S and Equatorthe tropics, between 10S and Equator

Opposite-sign Opposite-sign discrepancydiscrepancywith respect to with respect to previous slide: previous slide: GEOS-5 analysesGEOS-5 analysesproduce produce stronger stronger easterly flow than easterly flow than NCEP)NCEP)

NCEPNCEP

GEOS-5GEOS-5

Additional vertical soundings at Cape Verde during Additional vertical soundings at Cape Verde during SOP-3 provided the chance to validate operational SOP-3 provided the chance to validate operational

analyses in 2006analyses in 2006

One of the rare cases in which One of the rare cases in which NCEPNCEP and and GEOS-5GEOS-5 differ less than 5 m/s) differ less than 5 m/s)

Both NCEP and GEOS-5 miss theBoth NCEP and GEOS-5 miss theAEJ maximum at 600hPa. AEJ maximum at 600hPa. ErrorErrorlarger than 10 m/s at AJE level!!!larger than 10 m/s at AJE level!!!

NCEPNCEP vsvs

GEOS-5GEOS-5

obsobs

obsobs

Catastrophic Catastrophic non-systematicnon-systematic differences differences

NCEPNCEP provides a good representation of provides a good representation oflow-level and upper-level flows but misses low-level and upper-level flows but misses the AEJ. the AEJ. GEOS-5 GEOS-5 has huge errors at all levels has huge errors at all levels except at 600hPa.except at 600hPa.

NCEP NCEP and and GEOS-5 GEOS-5 both missboth missthe low-level flow, with the low-level flow, with NCEPNCEP having havinglarger errors.larger errors.

NCEPNCEP vsvs

GEOS-5GEOS-5

obsobs

obsobs

Catastrophic Catastrophic non-systematicnon-systematic differences differences

GEOS-5GEOS-5 has a stronger AEJ. has a stronger AEJ. NCEPNCEP has a stronger AEJ. has a stronger AEJ.

NCEPNCEP vsvs

GEOS-5GEOS-5

In addition to differences in the general circulation in In addition to differences in the general circulation in the Tropics, state-of-the-art operational systems can the Tropics, state-of-the-art operational systems can

completely miss completely miss existingexisting Tropical Cyclones. Tropical Cyclones.

Analyses are particularly deficient in the depiction of Analyses are particularly deficient in the depiction of developing, deepeningdeveloping, deepening and and transitioning transitioning tropical cyclonestropical cyclones

Analyses are deficient in representing cyclogenesis and Analyses are deficient in representing cyclogenesis and existing deepening cyclones in the existing deepening cyclones in the eastern Atlanticeastern Atlantic

Analyses are Analyses are particularly deficientparticularly deficient in representing even in representing even fully-developed fully-developed TCs over the Indian Ocean TCs over the Indian Ocean

TS Debby (2006) at 06z 24 Aug 2006TS Debby (2006) at 06z 24 Aug 2006Obs center slp 999 hPa; Max wind 22 m/sObs center slp 999 hPa; Max wind 22 m/s

NCEP analysesNCEP analysesdo do notnot produce produce

a a closed closed circulationcirculation

GEOS-5 An.GEOS-5 An.200km200km

displacement displacement error for centererror for center(obs. center X) (obs. center X)

Wind speed m/sWind speed m/s

Published study on the impact of AIRS, Published study on the impact of AIRS, focused on tropical cyclone Nargis (2008)focused on tropical cyclone Nargis (2008)emphasizes the difficulty of analysing TCs emphasizes the difficulty of analysing TCs

over the Indian Oceanover the Indian Ocean

Work published in 2009 shows some improvements in analysis over the Work published in 2009 shows some improvements in analysis over the tropicstropics in in the GEOS-5 DAS and forecasting model consequent to in in the GEOS-5 DAS and forecasting model consequent to assimilation of AIRS-derived information in assimilation of AIRS-derived information in CLOUDY CLOUDY areas. Case areas. Case chosen: chosen: catastrophic cyclone Nargis which hit Burma causing catastrophic cyclone Nargis which hit Burma causing devastating loss of lifedevastating loss of life

Tropical Cyclones in the Northern Indian Oceans are extremely difficult Tropical Cyclones in the Northern Indian Oceans are extremely difficult to analyze: operational global analyses often do not represent these to analyze: operational global analyses often do not represent these cyclones’ cyclones’ position position (or (or even the TCs’ very existenceeven the TCs’ very existence) accurately. ) accurately. Forecasts are penalized by these poor analysesForecasts are penalized by these poor analyses

Reale, O., W. K. Lau, J. Susskind, R. Rosenberg, E. Brin, E. Liu, L.P. Riishojgaard, M. Fuentes, Reale, O., W. K. Lau, J. Susskind, R. Rosenberg, E. Brin, E. Liu, L.P. Riishojgaard, M. Fuentes, R. Rosenberg, 2009: AIRS impact on the analysis and forecast track of tropical cyclone Nargis in R. Rosenberg, 2009: AIRS impact on the analysis and forecast track of tropical cyclone Nargis in A global data assimilation and forecasting system. A global data assimilation and forecasting system. Geophys. Res. Lett., 36, L06812, doi: 10.1029/2008GL037122Geophys. Res. Lett., 36, L06812, doi: 10.1029/2008GL037122

Complete Complete miss of TC Nargismiss of TC Nargis (2008) in both (2008) in both operational NCEPoperational NCEP and and MERRAMERRA analyses at a analyses at a time when is declared having time when is declared having hurricane-level hurricane-level

windswinds by the JTPC and IMC by the JTPC and IMC

800x600km800x600kmContours Contours every 1hPaevery 1hPa

WINDS DOWINDS DONOT FORMNOT FORMA CLOSEDA CLOSEDCIRCULATIONCIRCULATION

800x600km800x600kmContours Contours every 1hPaevery 1hPa

X observed X observed cyclone’s center cyclone’s center

COMPLETELYCOMPLETELYFLAT PRESSUREFLAT PRESSURE

FIELDFIELD

WINDS DO NOT REACH 12m/sWINDS DO NOT REACH 12m/sWINDS DO NOT FORM A CLOSED CIRCULATIONWINDS DO NOT FORM A CLOSED CIRCULATION

Some improvement with AIRS Some improvement with AIRS cloudycloudy retrievals retrievals

Analysis obtained Analysis obtained assimilating AIRS assimilating AIRS cloudycloudy retrievals retrievalsWell-definedWell-definedCycloneCycloneGreen:Green:Observed Observed TrackTrack

108-hour108-hourforecast (slp)forecast (slp)initialized from initialized from improved improved analysesanalyses

Green:Green:Observed Observed TrackTrack

CNTRL Analysis (above)CNTRL Analysis (above)And forecast (below): And forecast (below): No CycloneNo Cyclone

Accurate landfall is produced in the forecasts initialized Accurate landfall is produced in the forecasts initialized with AIRS: (Reale et al., 2009, with AIRS: (Reale et al., 2009, Geophys. Res. LettGeophys. Res. Lett.).)

Huge differences between operational ECMWF, Huge differences between operational ECMWF, NCEP and MERRA over the entire tropical Pacific NCEP and MERRA over the entire tropical Pacific

during strong La Nina conditions (Aug 2010)during strong La Nina conditions (Aug 2010)

Weather prediction over the tropical Pacific is Weather prediction over the tropical Pacific is controlled by a good representation of the controlled by a good representation of the predominantly easterly flow and periodic westerly predominantly easterly flow and periodic westerly bursts along the Equatorbursts along the Equator

Large errors in the equatorial flowLarge errors in the equatorial flow propagate propagate away from the Equatoraway from the Equator affecting affecting TC genesisTC genesis prediction, and prediction, and TC track forecastTC track forecast as far as 30N/S as far as 30N/S

HugeHuge 600hPa zonal wind difference 600hPa zonal wind difference affects the affects the entireentire tropical Pacific in tropical Pacific in 20102010

Speeds are very Speeds are very comparable away comparable away from the tropics.from the tropics.

Difference ofDifference ofabout about 10m/s10m/sover Eq.Pacificover Eq.Pacific

HugeHuge 600hPa zonal wind difference 600hPa zonal wind difference affects the affects the entireentire tropical Pacific in tropical Pacific in 20102010

50% speed50% speedDifference Difference Over Eq.Over Eq.PacificPacific

Opposite sign Opposite sign wind over, wind over, and NE of, and NE of, HawaiiHawaii

HugeHuge 600hPa zonal wind difference 600hPa zonal wind difference affects the affects the entireentire tropical Pacific in tropical Pacific in 20102010

involving all 3 data setsinvolving all 3 data sets

The largest 600hPa wind difference at 165W occurs The largest 600hPa wind difference at 165W occurs in the tropics, between in the tropics, between 20S and 10N20S and 10N

MERRAMERRA

ECMWFECMWF

NCEPNCEP

ConclusionsConclusions State of the art reanalyses State of the art reanalyses (ERA-40, JRA-25, NCEP-R2 and MERRA)(ERA-40, JRA-25, NCEP-R2 and MERRA) show show

susbtantial differences in the susbtantial differences in the seasonally-averaged seasonally-averaged representation of the representation of the African Easterly JetAfrican Easterly Jet and more generally of the circulation in the African and more generally of the circulation in the African Monsoon and tropical Atlantic regionsMonsoon and tropical Atlantic regions

Operational analyses or reanalyses differ also at Operational analyses or reanalyses differ also at instantaneous timesinstantaneous times in the in the tropical region. On the contrary, away from the tropics, different analyses tropical region. On the contrary, away from the tropics, different analyses provide almost identical representations of the wind fieldprovide almost identical representations of the wind field

Some limited improvement in the analysis and forecast in the tropics has Some limited improvement in the analysis and forecast in the tropics has been been locallylocally noted as a consequence of particular methodologies, such as noted as a consequence of particular methodologies, such as cloudy AIRS retrieval ingestion, or implementation of interactive aerosols. cloudy AIRS retrieval ingestion, or implementation of interactive aerosols.

However, it appears evident that However, it appears evident that the global tropical wind fieldthe global tropical wind field is the most is the most deficient aspect of current tropospheric analysisdeficient aspect of current tropospheric analysis

Despite changes in models and assimilation systems, and increase in Despite changes in models and assimilation systems, and increase in resolution, resolution, the representation of wind in the tropicsthe representation of wind in the tropics does not show much does not show much improvementimprovement from from 2006 to 20102006 to 2010

Major deficiencies appear on Major deficiencies appear on all 3 basins:all 3 basins: Atlantic, Indian and Pacific OceansAtlantic, Indian and Pacific Oceans on scales spanning from on scales spanning from storm-scalestorm-scale to to planetaryplanetary, from , from weatherweather to to seasonalseasonal

To reduce the errors in the analyzed wind field on different scales in To reduce the errors in the analyzed wind field on different scales in the tropics is of paramount importance and should be the goal for the the tropics is of paramount importance and should be the goal for the next-generation observing systemsnext-generation observing systems