atelier adomoca 13-15 décembre 2005 projets autour de l’sssimilation multi- capteurs spatiaux au...
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Atelier ADOMOCA 13-15 décembre 2005
Projets autour de l’sssimilation multi-capteurs spatiaux au LA pour l’étude des processus physico-
chimiques dans l’UTLS
Brice Barret, Philippe Ricaud, Jean-Luc Attié, Eric LeflochmoënLaboratoire d’Aérologie, Observatoire Midi-Pyrénées, Toulouse, France
Collaborations: CNRM, CERFACS
Atelier ADOMOCA 13-15 décembre 2005
Problématique
Processus dynamiques et chimiques dans l’UTLS
Plan• Instruments spatiaux impliqués
• Validation croisée Odin/SMR vs. Aura/MLS
• SMR/CO dans la basse stratosphère Comparaison avec MOPITT
• Impact de la circulation atmosphérique sur la distribution des
gaz Stratosphère: Brewer-Dobson Troposphère : Hadley, Walker
• Echanges troposphère-stratosphère
• Conclusions et perspectives
Chimie de l’ozone stratosphériqueImpact radiatif (ozone, vapeur d’eau)Processus de déshydratation dans la TTLAugmentation de la vapeur d’eau stratosphérique
Peu d’information à l’échelle globale (satellites)
Atelier ADOMOCA 13-15 décembre 2005
Odin/SMR, Aura/MLS…Sondage de la stratosphère
couche d’ozone
Metop/IASI, Terra/MOPITT, Aqua/AIRS…Sondage de la troposphère
pollution, climat
MTG, GeoTROPE, TRAQ…?Sondage de la troposphère
pollutions locales et régionales
Les missions spatiales impliquées
Atelier ADOMOCA 13-15 décembre 2005
Cross-Validation Odin/SMR vs. Aura/MLS
• Good agreement from 100 to 1 hPa
• MLS > SMR ~ 20% from 30 to 1 hPa at high lat.
• MLS < SMR up to 40% above 20 hPa in the tropics and at mid. Lat.
• MLS > SMR below ~ 30 hPa at all latitudes
• R > 0.8 from 68.1 to 6.8 hPa
Consistent with MLS comparisons with SAGEII and ACE (Froidevaux et al., 2005)
O3
Atelier ADOMOCA 13-15 décembre 2005
• Excellent agreement from 68.1 to 1 hPa
• MLS > SMR in the LS bias up to 60% at 147 hPa at high north. lat.
• MLS < SMR above 68.1 hPa 10-15%
• SMR noisier than MLS
High bias from MLS (up to 60 ppbv) in the LS polar vortices (Froidevaux et al., 2005)
Cross-Validation Odin/SMR vs. Aura/MLSN2O
Atelier ADOMOCA 13-15 décembre 2005
• Good agreement from 14.6 to 0.1 hPa
• MLS > SMR above 0.1 hPa
• MLS profiles are strongly oscillating
• MLS has permanent negative values in the tropics and high north. lat.
• High correlations in the upper stratosphere (around 6.8 hPa)
Cross-Validation Odin/SMR vs. Aura/MLSCO
Atelier ADOMOCA 13-15 décembre 2005
CO in the Lower Stratosphere
January 2004 February2004
July 2004 September 2004
High CO concentrationsin the LS in the winter at high latitudes
SMR Zonal means
Artifact ?A priori effect ?
Atelier ADOMOCA 13-15 décembre 2005
SMR at 18 km
CO in the Lower Stratosphere
MOPITT at 150 hPa
Northern Hemisphere
Atelier ADOMOCA 13-15 décembre 2005
SMR at 18 km MOPITT at 150 hPa
CO in the Lower Stratosphere
Southern Hemisphere
Atelier ADOMOCA 13-15 décembre 2005
Stratospheric circulation
HALOE CH4
NH Winter
SH Winter
Brewer/Dobson diabatic circulation• Braking of Gravity/Planetary waves• Mesosphere: summer to winter pole• Stratosphere: tropics to winter poleTropical/vortex barriersSurf zone (isentropic mixing)
Atelier ADOMOCA 13-15 décembre 2005
Tropospheric meridional circulation
The Hadley Cells:• Energy imbalance between the tropics and the pole• Convective rising of warm moist tropical air in the tropics (ITCZ)• Return of the diverging upper-level cool dry air to the surface poleward of the Equator • Movement of air towards the convergence zone at the Equator (Trade Winds)
Seasonal variations:• Shift in the location of the maximum tropical heating • Single North/South Hadley cell in January/July• Dual North/South Hadley cells symmetric/Equator in April/October
Waliser et al., Climate Dynamics, 1999
Atelier ADOMOCA 13-15 décembre 2005
Tropospheric meridional circulation
MOPITT• Meridional/Vertical transport of CO• Seasonal variability: mixture between
• Sources: biomass burning • Hadley cells
MOCAGE-Climat/MOPITT• MOPITT low vertical resolution• MOCAGE-Climat sources ?
Further work:• Meteorological context • MOCAGE sources• Convolution of MOCAGE with MOPITT averaging kernels• Assimilated MOPITT CO within MOCAGE
Impact on the distribution of tropospheric trace gases ?
Atelier ADOMOCA 13-15 décembre 2005
Walker circulation / ENSONormal conditions:• Western Pacific 3 to 8° warmer than Eastern Pacific• Trade winds bring warm moist air towards Indonesia• Rises over warm seas (clouds, rain)• Travels Eastward and sinks over Eastern Pacific (clear, dry)
El Niño conditions:• Central or Eastern Pacific as warm or warmer than Western Pacific…
SOI
SOI strongly negative
SOI close to zero
Atelier ADOMOCA 13-15 décembre 2005
Walker circulation / ENSO
CO: • Longitudianal/Vertical transport• Evidence of 3 main cells from MOPITT data in non el Niño conditions• No data in el Niño conditions
Impact on the distribution of tropospheric trace gases ?
Africa Indonesia South America
O3: • ENSO : strong impact on STE• El Niño (October 1997): strong increase of O3 over western Pacific and decrease over the eastern Pacific (TOMS data)
Zeng and Pyle, GRL, 2005
Atelier ADOMOCA 13-15 décembre 2005
Stratosphere Troposphere Exchange
Stohl et al., BAMS, 2003
Overworld
Lowermost stratosphere
Free Troposphere
ABL
Tropical Transition Layer
•Slow ascent in the tropics and descent in polar regions
•Isentropic transport between the tropical free troposphere and the extratroical lowermost stratosphere
•Deep stratospheric intrusions
•Warm conveyor belts…
Atelier ADOMOCA 13-15 décembre 2005
Multi-sensor couplingSH Winter
UTLS ~12-18 km
Limb Stratospheric Sounder:Odin/SMR, Aura/MLS,
Envisat/MIPAS…• High vertical resolution (2-4 km)• Low horizontal sampling (> 100 km)• Low sensitivity in the UTLS
Nadir Tropospheric Sounder:Terra/MOPITT,
Aqua/AIRS, Metop/IASI…• Low vertical resolution (> 6 km)• High horizontal sampling and resolution• Low sensitivity in the UTLS
SMR
MOPITT
Coupling of data from a Stratospheric and a Tropospheric sounder in MOCAGE via the assimilation coupler PALM information in the UTLS
Atelier ADOMOCA 13-15 décembre 2005
Conclusions
MLS vs. SMR O3 and N2O: good agreement
CO: MLS V1.5 displays strong oscillations
SMR CO in the lower stratosphereIncrease of CO at high latitudes in winter ?
Atmospheric circulationStratosphere : general features seen by all the limb sounders with long-lived tracers
Troposphere: • Mean meridional circulation not directly evident from MOPITT• Walker circulation: evidence from MOPITT
Stratosphere-Troposphere exchanges Nadir viewing instruments: low vertical resolutionLimb sounders: low sensitivity in the UTLS/TTL Need to couple both type of observations via assimilation (PALM/MOCAGE)
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