J. Flaud - Academia.edu (original) (raw)

Papers by J. Flaud

The POGEQA (Observation of Air Quality from a Geostationary Platform) project is a French and Ger... more The POGEQA (Observation of Air Quality from a Geostationary Platform) project is a French and German initiative currently funded by RTRA STAE (Midi-Pyrenees region). It links also with other international teams and initiatives sharing similar objectives, such as GEOCAPE. Using a sophisticated chemical data assimilation system, MOCAGE-PALM, POGEQA aims at defining optimal characteristics for a future instrument in geostationary orbit complementing orbiting instruments and surface observations for Air Quality monitoring and forecasting. POGEQA sits also in the context of the european initiative GMES (Global Monitoring for Environment and Security) and the project MACC, which aims at assembling operational atmospheric services ; MOCAGE-PALM is indeed one of the pre-operational systems upon which the production of regional Air Quality products is based. These experiments comprise both assimilation of currently existing sensors for tropospheric ozone and CO, such as IASI and MOPITT, and assimilation of synthetic data (OSSEs, Observing System Simulation Experiments) representative of possible geostationary instrumental concepts. These numerical experiments, though representing a very small fraction of the cost compared to the development of a real test instrument, will allow to justify quantitatively the requirements (geometry, sensitivity, errors,...). Differents aspects of operating such an instrument in real conditions (clouds, observations with representativeness errors, radiances...) can also be considered. We will show highlights from the first results obtained in the project. In particular, we will present the synthetic observations generating tool, which is based upon the KOPRA and KOPRAFIT models and 3D chemical scenes produced with chemical models CHIMERE and/or MOCAGE. We will discuss also findings from assimilation experiments and OSSEs.

For the measurement of atmospheric ozone concentrations, the mid-infrared and ultraviolet regions... more For the measurement of atmospheric ozone concentrations, the mid-infrared and ultraviolet regions are both used by ground-, air-, or satellite-borne instruments. In this study we report the first laboratory intercomparison of the ozone absorption coefficients using simultaneous measurements in these spectral regions. The intercomparison shows good agreement (around 98.5%) between the HITRAN 2000 recommendation for the mid-infrared and the most reference measurements in the ultraviolet regions, whereas systematic differences of about 5.5% are observed when using the recommendation of HITRAN2003 for the mid-infrared. Possible reasons for this discrepancy are discussed. Future measurements are clearly needed to resolve this issue. * Corresponding author. Telephone: 33 (1) 45 17 15 90. Fax: 33 (1) 45 17 15 64.

One of the major challenges facing atmospheric sciences is to assess, understand and quantify the... more One of the major challenges facing atmospheric sciences is to assess, understand and quantify the impact of natural and anthropogenic pollution on the quality of life on Earth on a local, regional and continental scale. To understand the effects of regional pollution on a continental scale there is the requirements to link diurnal with seasonal and annual timescales, as well

Atmospheric Chemistry and Physics, 2012

A detailed 3-D evaluation of an ensemble of five regional Chemistry Transport Models (RCTM) and o... more A detailed 3-D evaluation of an ensemble of five regional Chemistry Transport Models (RCTM) and one global CTM with focus on free tropospheric ozone over Europe is presented. It is performed over a summer period (June to August 2008) in the context of the GEMS-RAQ project. A data set of about 400 vertical ozone profiles from balloon soundings and commercial aircraft at 11 different locations is used for model evaluation, in addition to satellite measurements with the infrared nadir sounder (IASI) showing largest sensitivity to free tropospheric ozone. In the middle troposphere, the four regional models using the same top and boundary conditions from IFS-MOZART exhibit a systematic negative bias with respect to observed profiles of about −20 %. Root Mean Square Error (RMSE) values are constantly growing with altitude, from 22 % to 32 % to 53 %, respectively for 0-2 km, 2-8 km and 8-10 km height ranges. Lowest correlation is found in the middle troposphere, with minimum coefficients (R) between 0.2 to 0.45 near 8 km, as compared to 0.7 near the surface and similar values around 10 km. A sensitivity test made with the CHIMERE mode also shows that using hourly instead of monthly chemical boundary conditions generally improves the model skill (i.e. improve RMSE and correlation). Lower tropospheric 0-6 km partial ozone columns derived from IASI show a clear North-South gradient over Europe, which is qualitatively reproduced by the models. Also the temporal variability showing decreasing ozone concentrations in the lower troposphere (0-6 km columns) during summer is well reproduced by models even if systematic bias remains (the value of the bias being also controlled by the type of used boundary conditions). A multi-day case study of a trough with low tropopause was conducted and showed that both IASI and models were able to resolve strong horizontal gradients of middle and upper tropospheric ozone occurring in the vicinity of an upper tropospheric frontal zone.

The POGEQA (Observation of Air Quality from a Geostationary Platform) project is a French and Ger... more The POGEQA (Observation of Air Quality from a Geostationary Platform) project is a French and German initiative currently funded by RTRA STAE (Midi-Pyrenees region). It links also with other international teams and initiatives sharing similar objectives, such as GEOCAPE. Using a sophisticated chemical data assimilation system, MOCAGE-PALM, POGEQA aims at defining optimal characteristics for a future instrument in geostationary orbit complementing orbiting instruments and surface observations for Air Quality monitoring and forecasting. POGEQA sits also in the context of the european initiative GMES (Global Monitoring for Environment and Security) and the project MACC, which aims at assembling operational atmospheric services ; MOCAGE-PALM is indeed one of the pre-operational systems upon which the production of regional Air Quality products is based. These experiments comprise both assimilation of currently existing sensors for tropospheric ozone and CO, such as IASI and MOPITT, and assimilation of synthetic data (OSSEs, Observing System Simulation Experiments) representative of possible geostationary instrumental concepts. These numerical experiments, though representing a very small fraction of the cost compared to the development of a real test instrument, will allow to justify quantitatively the requirements (geometry, sensitivity, errors,...). Differents aspects of operating such an instrument in real conditions (clouds, observations with representativeness errors, radiances...) can also be considered. We will show highlights from the first results obtained in the project. In particular, we will present the synthetic observations generating tool, which is based upon the KOPRA and KOPRAFIT models and 3D chemical scenes produced with chemical models CHIMERE and/or MOCAGE. We will discuss also findings from assimilation experiments and OSSEs.

Advances in Space Research, 2004

Paris 7-Paris 12, CNRS UMR7583, 61 av. du G en eral de Gaulle,

Comptes Rendus Physique, 2005

This paper presents the Geostationary Fourier Imaging Spectrometer (GeoFIS), a new satellite inst... more This paper presents the Geostationary Fourier Imaging Spectrometer (GeoFIS), a new satellite instrument that has been proposed to monitor tropospheric key pollutants (O 3 , CO) in order to improve the predictive capability of tropospheric chemistry models. The horizontal resolution of GeoFIS is about 15 × 15 km 2 and the temporal resolution is about 60 minutes. It is shown that the current instrument concept (based on available or under development optical, detector and platform technologies) is sufficient to provide tropospheric concentrations of O 3 and CO as well as columns of species like PAN with the required accuracies. To cite this article: J. Orphal et al., C. R. Physique 6 (2005).  2005 Académie des sciences. Published by Elsevier SAS. All rights reserved. Résumé Surveillance de la pollution troposphérique par spectroscopie infrarouge à partir d'une orbite géostationnaire. Dans cet article nous présentons le « Geostationary Fourier Imaging Spectrometer » (GeoFIS), un nouvel instrument satellite qui a été proposé pour surveiller les polluants troposphériques les plus importants (O 3 , CO) afin d'améliorer la précision des prédictions fournies par les modèles de la chimie troposphérique. La résolution horizontale de GeoFIS est de 15 × 15 km 2 environ et la résolution temporelle est de 60 minutes. Nous montrons que le concept actuel de cet instrument (basé sur des technologies optiques, détecteur et plateforme disponibles ou en développement) est bien adapté pour fournir des concentrations troposphériques d'O 3 et de CO, ainsi que des colonnes d'espèces comme le PAN, avec les précisions requises. Pour citer cet article : J. Orphal et al., C. R. Physique 6 (2005).

The POGEQA (Observation of Air Quality from a Geostationary Platform) project is a French and Ger... more The POGEQA (Observation of Air Quality from a Geostationary Platform) project is a French and German initiative currently funded by RTRA STAE (Midi-Pyrenees region). It links also with other international teams and initiatives sharing similar objectives, such as GEOCAPE. Using a sophisticated chemical data assimilation system, MOCAGE-PALM, POGEQA aims at defining optimal characteristics for a future instrument in geostationary orbit complementing orbiting instruments and surface observations for Air Quality monitoring and forecasting. POGEQA sits also in the context of the european initiative GMES (Global Monitoring for Environment and Security) and the project MACC, which aims at assembling operational atmospheric services ; MOCAGE-PALM is indeed one of the pre-operational systems upon which the production of regional Air Quality products is based. These experiments comprise both assimilation of currently existing sensors for tropospheric ozone and CO, such as IASI and MOPITT, and assimilation of synthetic data (OSSEs, Observing System Simulation Experiments) representative of possible geostationary instrumental concepts. These numerical experiments, though representing a very small fraction of the cost compared to the development of a real test instrument, will allow to justify quantitatively the requirements (geometry, sensitivity, errors,...). Differents aspects of operating such an instrument in real conditions (clouds, observations with representativeness errors, radiances...) can also be considered. We will show highlights from the first results obtained in the project. In particular, we will present the synthetic observations generating tool, which is based upon the KOPRA and KOPRAFIT models and 3D chemical scenes produced with chemical models CHIMERE and/or MOCAGE. We will discuss also findings from assimilation experiments and OSSEs.

For the measurement of atmospheric ozone concentrations, the mid-infrared and ultraviolet regions... more For the measurement of atmospheric ozone concentrations, the mid-infrared and ultraviolet regions are both used by ground-, air-, or satellite-borne instruments. In this study we report the first laboratory intercomparison of the ozone absorption coefficients using simultaneous measurements in these spectral regions. The intercomparison shows good agreement (around 98.5%) between the HITRAN 2000 recommendation for the mid-infrared and the most reference measurements in the ultraviolet regions, whereas systematic differences of about 5.5% are observed when using the recommendation of HITRAN2003 for the mid-infrared. Possible reasons for this discrepancy are discussed. Future measurements are clearly needed to resolve this issue. * Corresponding author. Telephone: 33 (1) 45 17 15 90. Fax: 33 (1) 45 17 15 64.

One of the major challenges facing atmospheric sciences is to assess, understand and quantify the... more One of the major challenges facing atmospheric sciences is to assess, understand and quantify the impact of natural and anthropogenic pollution on the quality of life on Earth on a local, regional and continental scale. To understand the effects of regional pollution on a continental scale there is the requirements to link diurnal with seasonal and annual timescales, as well

Atmospheric Chemistry and Physics, 2012

A detailed 3-D evaluation of an ensemble of five regional Chemistry Transport Models (RCTM) and o... more A detailed 3-D evaluation of an ensemble of five regional Chemistry Transport Models (RCTM) and one global CTM with focus on free tropospheric ozone over Europe is presented. It is performed over a summer period (June to August 2008) in the context of the GEMS-RAQ project. A data set of about 400 vertical ozone profiles from balloon soundings and commercial aircraft at 11 different locations is used for model evaluation, in addition to satellite measurements with the infrared nadir sounder (IASI) showing largest sensitivity to free tropospheric ozone. In the middle troposphere, the four regional models using the same top and boundary conditions from IFS-MOZART exhibit a systematic negative bias with respect to observed profiles of about −20 %. Root Mean Square Error (RMSE) values are constantly growing with altitude, from 22 % to 32 % to 53 %, respectively for 0-2 km, 2-8 km and 8-10 km height ranges. Lowest correlation is found in the middle troposphere, with minimum coefficients (R) between 0.2 to 0.45 near 8 km, as compared to 0.7 near the surface and similar values around 10 km. A sensitivity test made with the CHIMERE mode also shows that using hourly instead of monthly chemical boundary conditions generally improves the model skill (i.e. improve RMSE and correlation). Lower tropospheric 0-6 km partial ozone columns derived from IASI show a clear North-South gradient over Europe, which is qualitatively reproduced by the models. Also the temporal variability showing decreasing ozone concentrations in the lower troposphere (0-6 km columns) during summer is well reproduced by models even if systematic bias remains (the value of the bias being also controlled by the type of used boundary conditions). A multi-day case study of a trough with low tropopause was conducted and showed that both IASI and models were able to resolve strong horizontal gradients of middle and upper tropospheric ozone occurring in the vicinity of an upper tropospheric frontal zone.

The POGEQA (Observation of Air Quality from a Geostationary Platform) project is a French and Ger... more The POGEQA (Observation of Air Quality from a Geostationary Platform) project is a French and German initiative currently funded by RTRA STAE (Midi-Pyrenees region). It links also with other international teams and initiatives sharing similar objectives, such as GEOCAPE. Using a sophisticated chemical data assimilation system, MOCAGE-PALM, POGEQA aims at defining optimal characteristics for a future instrument in geostationary orbit complementing orbiting instruments and surface observations for Air Quality monitoring and forecasting. POGEQA sits also in the context of the european initiative GMES (Global Monitoring for Environment and Security) and the project MACC, which aims at assembling operational atmospheric services ; MOCAGE-PALM is indeed one of the pre-operational systems upon which the production of regional Air Quality products is based. These experiments comprise both assimilation of currently existing sensors for tropospheric ozone and CO, such as IASI and MOPITT, and assimilation of synthetic data (OSSEs, Observing System Simulation Experiments) representative of possible geostationary instrumental concepts. These numerical experiments, though representing a very small fraction of the cost compared to the development of a real test instrument, will allow to justify quantitatively the requirements (geometry, sensitivity, errors,...). Differents aspects of operating such an instrument in real conditions (clouds, observations with representativeness errors, radiances...) can also be considered. We will show highlights from the first results obtained in the project. In particular, we will present the synthetic observations generating tool, which is based upon the KOPRA and KOPRAFIT models and 3D chemical scenes produced with chemical models CHIMERE and/or MOCAGE. We will discuss also findings from assimilation experiments and OSSEs.

Advances in Space Research, 2004

Paris 7-Paris 12, CNRS UMR7583, 61 av. du G en eral de Gaulle,

Comptes Rendus Physique, 2005

This paper presents the Geostationary Fourier Imaging Spectrometer (GeoFIS), a new satellite inst... more This paper presents the Geostationary Fourier Imaging Spectrometer (GeoFIS), a new satellite instrument that has been proposed to monitor tropospheric key pollutants (O 3 , CO) in order to improve the predictive capability of tropospheric chemistry models. The horizontal resolution of GeoFIS is about 15 × 15 km 2 and the temporal resolution is about 60 minutes. It is shown that the current instrument concept (based on available or under development optical, detector and platform technologies) is sufficient to provide tropospheric concentrations of O 3 and CO as well as columns of species like PAN with the required accuracies. To cite this article: J. Orphal et al., C. R. Physique 6 (2005).  2005 Académie des sciences. Published by Elsevier SAS. All rights reserved. Résumé Surveillance de la pollution troposphérique par spectroscopie infrarouge à partir d'une orbite géostationnaire. Dans cet article nous présentons le « Geostationary Fourier Imaging Spectrometer » (GeoFIS), un nouvel instrument satellite qui a été proposé pour surveiller les polluants troposphériques les plus importants (O 3 , CO) afin d'améliorer la précision des prédictions fournies par les modèles de la chimie troposphérique. La résolution horizontale de GeoFIS est de 15 × 15 km 2 environ et la résolution temporelle est de 60 minutes. Nous montrons que le concept actuel de cet instrument (basé sur des technologies optiques, détecteur et plateforme disponibles ou en développement) est bien adapté pour fournir des concentrations troposphériques d'O 3 et de CO, ainsi que des colonnes d'espèces comme le PAN, avec les précisions requises. Pour citer cet article : J. Orphal et al., C. R. Physique 6 (2005).