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Brice Barret, Eric Le Flochmoën Equipe O 3 et précurseurs, Laboratoire d’Aérologie

Assimilation des observations MLS Transport d’espèces chimiques de l’Asie vers l’Afrique dans l’UT Chaine de traitement des données IASI pour la restitution de profils de CO et d’O 3. Brice Barret, Eric Le Flochmoën Equipe O 3 et précurseurs, Laboratoire d’Aérologie

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Brice Barret, Eric Le Flochmoën Equipe O 3 et précurseurs, Laboratoire d’Aérologie

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  1. Assimilation des observations MLSTransport d’espèces chimiques de l’Asie vers l’Afrique dans l’UTChaine de traitement des données IASI pour la restitution de profils de CO et d’O3 Brice Barret, Eric Le Flochmoën Equipe O3 et précurseurs, Laboratoire d’Aérologie CNRS / Université Paul Sabatier Toulouse, France Collaborateurs ADOMOCA Toulouse

  2. Transport pathways of chemicals from Asia to Africa • General context • O3 = greenhouse gas + pollutant • Precursor emissions, transport, chemistry and radiations • CO = O3 precursor, pollution tracer (lifetime > 1 month) • Emissions and transport • West African and Asian Monsoons = uplift of polluted air masses into the UT • Scientific questions • Main transport pathways of CO/O3 to the African UT ? • Interconnections between the Asian and African UT ? • Photochemical production of O3 during transport ? • Reasons for the synoptic variability of CO/O3 over Africa ? • Method • Assimilation of sparse spaceborne observations into a global CTM to provide realistic 4D CO/O3 distributions with a synoptic time resolution.

  3. Transport pathways of chemicals from Asia to Africa Carbon monoxide Biomass Burning inventories over Africa Activity within AMMA : Western African Monsoon in 2006 African BB: AMMA-LA African BB: GFED MOCAGE MOPITT MOPITT MOCAGE MOCAGE*AK MOCAGE*AK African BB: NOx: 5.5 TgN/year CO: 119 TgC/year African BB: NOx: 1.6 TgN/year CO: 64 TgC/year • Higher BB emissions from AMMA-LA lead to a better agreement with MOPITT • CO transport from southern Africa to the Guinea Gulf is misrepresented • Impact on O3 has to be evaluated against satellite observations

  4. Transport pathways of chemicals from Asia to Africa Carbon monoxide CO@200 hPa (07/2006) • Main transport processes • South African BB CO uplifted within the WAM region to ~ 180 hPa. • Asian pollution uplifted during ASM south of TP / SW China to the LS ~ 100 hPa. • Asian pollution trapped within the AMA up to the LS. • UT transport from Asia to Northern Africa and the Mediterranean by AMA and TEJ. • Model versus Assimilation • UT Asian CO too low: low emissions / uplift processes / chemistry ? • African UT CO too high south of WAM: south African BB emissions too high ? Assimilated MLS TP AMA ASM TEJ WAM MOCAGE (BB Africa: AMMA-LA)

  5. Transport pathways of chemicals from Asia to Africa Carbon monoxide Assimilated MLS CO at 200 hPa (07/2006) • Synoptic transport processes • Assimilated fields versus satellite observations: 4D distributions (12h resolution). • Between 25-35°N the CO UT distribution is driven by the elongations and shedding of the AMA. • Around 21 July, an anomalous propagation of the TEJ transports an Asian CO plume to the African Atlantic coast and northward to the western Mediterannean.

  6. Transport pathways of chemicals from Asia to Africa Carbon monoxide Transport of CO by the TEJ MOCAGE-MLS CO 150 hPa / 15-25°N Simulation / assimilation / in-situ CO Averaged over 15-25°N MOZAIC Easterly winds 10 m/s MOCAGE MOCAGE-MLS Day of July 2006 anomalous CO transport from Asia to Africa by the TEJ MOZAIC (Namibia-Germany) flight longitude Model: problem with emissions or uplift ? Longitude Barret et al., ACP, 2008

  7. Transport pathways of chemicals from Asia to Africa Carbon monoxide Transport of CO by the AMA • AMA characterised by low PV (1.5 PVU taken as criterium at 150 hPa) • mean extension to 0°E at 150 hPa • dynamic instabilities: periodic sheddings into secondary anticyclones and elongations • CO maxima correlated to PV minima PV 150 hPa / 25-35°N MOCAGE-MLS CO 150 hPa / 25-35°N Weak vortex 1.5 PVU Shedding Elongation Day of July 2006 Shedding Westward propagation 25°E

  8. Transport pathways of chemicals from Asia to Africa Carbon monoxide Validation for the whole summer Assimilation with the linearised CO scheme R(MOZAIC-SIMUL)=0.3 R(MOZAIC-ASSIM)=0.7 (Racmobus) 20-30°N 15 May 30 September

  9. Transport pathways of chemicals from Asia to Africa Ozone O3@200 hPa (07/2006) • Model versus assimilation • The general O3 structure well represented by the model • Overestimation of UT O3 maxima within the AMA and over Africa • Scientific issues • Origin of the O3 UT maximum within AMA over Middle-east: stratosphere / Li-NOx / Asian emissions • Impact of this enhanced AMA O3 over Africa / Mediterranean • Reason of model overestimation: OH-chemistry, Convection/LiNOx, surface emissions Assimilated MLS (Linearised O3) MOCAGE (African BB: AMMA-LA)

  10. Transport pathways of chemicals from Asia to Africa Ozone Comparison MOCAGE-MOZAIC for the whole summer R(MOZAIC-SIMUL)=0.7 20-30°N

  11. Conclusions • Assimilation of MLS UTLS observations with MOCAGE-PALM provides CO and O3 distributions: • more realistic than the model in particular within the AMA • validated (CO) with the MOZAIC Air-Namibia observations over Africa • with a synoptic time resolution unachievable with the MLS observations • Identification of the main transport pathways of CO to the African UT during the monsoon season: • uplift within the Asian and African convective regions • synoptic variations modulated by the AMA elongations/sheddings (25-35°N band) • westward transport by the TEJ east of 15°E (15-25°N band) Perspectives • Quantitative determination of the air-masses origin • Setup of tagged-CO in MOCAGE: source region (Africa/Asia…) / type (BB / anthopogenic / NMVOC oxidation…) • Use of idealized tracers in the different source/convective regions • Impact of the different sources on UT O3 • sensitivity simulations: with-without convection/Li-NOx/surface NOx sources • assimilation of UTLS limb O3 observations on longer time periods and validation in the UT with MOZAIC • Identification of the causes of the model biases (e.g. too low (high) CO (O3) within the AMA)

  12. Chaîne de Traitement des données IASI au LA • Motivation • Produire des profils d’O3 et de CO sur des périodes longues et à l’échelle globale • Outils utilisés • Code de transfert radiatif rapide RTTOV de ECMWF • Module de restitution 1D-VAR de UKMO • Travaux effectués • Traitement des analyses ECMWF pour créer les fichiers d’entrée pour chaque pixel IASI • Pré-traitement des données L1C IASI • Mise en place d’un filtre nuageux basé sur la restitution de la température de surface • Premier test de restitution de profils d’O3 …

  13. Chaîne de Traitement des données IASI au LA Paramètres atmosphériques : Données ECMWF (grille 0.5°x0.5°) (P, T, Q, paramètres de surface, …) Spectres calibrés Ether -> L1C IASI Données a priori Pré-traitement  inputs par pixel RTTOV 1DVar Chaîne de traitement IASI au LA ( 1 ) ( 2 ) T surface No Ozone Nuage? Post-traitement  produits L2 Cartographie des paramètres inversés (Tsurf, O3, CO, …) Atelier ADOMOCA 13-14 novembre 2006

  14. Chaîne de Traitement des données IASI au LA Données a priori Ensemble de profils d’O3 IFS/ECMWF Variabilité globale/annuelle Matrice de Corrélation Profil a priori

  15. Chaîne de Traitement des données IASI au LA Filtre à nuage Nombre de pixels 18/07/2007 Europe T surf ECMWF Nuages opaques yes Nombre de pixels nuageux DT < -10° T surf IASI 831 no Nuages semi-transparents yes |DT| > 5° T surf IASI 957 Eremenko et al., GRL, 2008

  16. Chaîne de Traitement des données IASI au LA Restitution de profils d’ozone… 2007/07/18 Lindenberg: 54°N 11°E Tsurf=298°K DOFS=4 Profiles Spectres A priori IASI sonde Averaging Kernels 25 km 15 km 8 km 2 km

  17. Chaîne de Traitement des données IASI au LA • Travaux en perspective • Automatisation de la chaine de traitement (fichier utilisateur de lancement, enchainement des tâches) • Optimisation de la régularisation des restitutions (matrices de covariance a priori et instrumentale) • Optimisation du temps de calcul (coefficients RTTOV binaires…) • Assouplissement des limitations de RTTOV (nombre de niveau de pression…) • Outils de caractérisation (averaging kernels, matrices d’erreur…) • Définition et mise en place d’un format pour les sorties • Validation: mise en place d’une recherche automatique des coincidences IASI avec les profils MOZAIC CO+O3 (+WOUDC, SHADOZ pour O3) • Collaborations • Interne pour la validation avec MOZAIC • Avec le Met-Office (1D-Var) et ECMWF (RTTOV) pour les mises à jour et le support technique • Avec les autres équipes impliquées dans le projet IASI/TOSCA (SA, LISA…) pour l’intercomparaison des L2

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