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)