Tropospheric Ozone Assessment Report: Present-day distribution and trends of tropospheric ozone relevant to climate and global atmospheric chemistry model evaluation

The Tropospheric Ozone Assessment Report (TOAR) is an activity of the International Global Atmospheric Chemistry Project. This paper is a component of the report, focusing on the present-day distribution and trends of tropospheric ozone relevant to climate and global atmospheric chemistry model evaluation. Utilizing the TOAR surface ozone database, several figures present the global distribution and trends of daytime average ozone at 2702 non-urban monitoring sites, highlighting the regions and seasons of the world with the greatest ozone levels. Similarly, ozonesonde and commercial aircraft observations reveal ozone’s distribution throughout the depth of the free troposphere. Long-term surface observations are limited in their global spatial coverage, but data from remote locations indicate that ozone in the 21st century is greater than during the 1970s and 1980s. While some remote sites and many sites in the heavily polluted regions of East Asia show ozone increases since 2000, many others show decreases and there is no clear global pattern for surface ozone changes since 2000. Two new satellite products provide detailed views of ozone in the lower troposphere across East Asia and Europe, revealing the full spatial extent of the spring and summer ozone enhancements across eastern China that cannot be assessed from limited surface observations. Sufficient data are now available (ozonesondes, satellite, aircraft) across the tropics from South America eastwards to the western Pacific Ocean, to indicate a likely tropospheric column ozone increase since the 1990s. The 2014–2016 mean tropospheric ozone burden (TOB) between 60˚N–60˚S from five satellite products is 300 Tg ± 4%. While this agreement is excellent, the products differ in their quantification of TOB trends and further work is required to reconcile the differences. Satellites can now estimate ozone’s global long-wave radiative effect, but evaluation is difficult due to limited in situ observations where the radiative effect is greatest

Exploitation des observations satellitaires IASI couplées à un modèle régional pour l'amélioration de la prévision des épisodes de pollution en ozone

Satellite observations now contribute to the monitoring of the tropospheric composition and the air quality forecasting by providing quantitative information on ozone and its precursors. The objective of this thesis was to exploit the coupling between IASI satellite observations, which was launched on board the MetOp platform in October 2006, and the model CHIMERE in order to document the improvement of the air quality forecasting. This thesis is based primarily on the retrieval of ozone concentrations from infrared spectra measured by the IASI instrument in order to retrieve total ozone columns and ozone partial columns especially in the troposphere. These measurements have been validated by independent observations: the total columns are compared to ultra-violet measurements provided by the satellite instrument GOME 2 (also on board the MetOp satellite) and the ground-based instruments of the Brewer-Dobson network but also infrared measurements (AIRS and TES). The partial columns are compared to ozonesonde measurements. Another component of my thesis was to prepare IASI data assimilation into the model CHIMERE, using a Kalman Filter Ensemble. This method allows the establishment of modelling error covariances from a set of different configurations of the model. In this context, work on the construction of an ensemble that best reflects the reality has been undertaken. The quality of the ensemble was evaluated in the vertical dimension and at the surface from different tools, which are all based on comparisons with observations.Les observations satellitaires contribuent désormais à la surveillance de la composition troposphérique et à la prévision de la qualité de l'air, en fournissant une information quantitative sur l'ozone et ses précurseurs. L'objectif de ces travaux de thèse a été d'exploiter le couplage entre les observations satellitaires IASI, qui a été lancé à bord du satellite MetOp en octobre 2006, et le modèle CHIMERE, afin de documenter l'amélioration de la prévision de la qualité de l'air. Ces travaux s'appuient d'abord sur l'inversion des concentrations d'ozone à partir des spectres infrarouges mesurés par l'instrument IASI pour restituer des colonnes totales d'ozone et des colonnes partielles d'ozone notamment dans la troposphère. Ces mesures ont été validées par des observations indépendantes : les colonnes totales sont comparées à des mesures ultra-violettes fournies par l'instrument satellitaire GOME-2 (également à bord du satellite MetOp) et les instruments au sol du réseau Brewer-Dobson mais également des mesures infrarouges (TES et AIRS). Les colonnes partielles sont, elles, comparées à des mesures de ballons sonde. Un autre volet de mes travaux de thèse consiste à préparer l'assimilation des données IASI dans le modèle CHIMERE, en utilisant un Filtre de Kalman d'Ensemble. Cette méthode permet d'établir les covariances des erreurs du modèle à partir d'un ensemble de différentes configurations du modèle. Dans ce contexte, un travail sur la construction d'un ensemble reflétant au mieux la réalité a été entrepris. La qualité de l'ensemble a été évaluée, dans la dimension verticale et en surface, à partir de différents outils, qui reposent tous sur des comparaisons aux observations

Exploitation des observations satellitaires IASI couplées à un modèle régional pour l'amélioration de la prévision des épisodes de pollution en ozone

Les observations satellitaires contribuent désormais à la surveillance de la composition troposphérique et à la prévision de la qualité de l'air, en fournissant une information quantitative sur l'ozone et ses précurseurs. L'objectif de ces travaux de thèse a été d'exploiter le couplage entre les observations satellitaires IASI, qui a été lancé à bord du satellite MetOp en octobre 2006, et le modèle CHIMERE, afin de documenter l'amélioration de la prévision de la qualité de l'air. Ces travaux s'appuient d'abord sur l'inversion des concentrations d'ozone à partir des spectres infrarouges mesurés par l instrument IASI pour restituer des colonnes totales d ozone et des colonnes partielles d'ozone notamment dans la troposphère. Ces mesures ont été validées par des observations indépendantes : les colonnes totales sont comparées à des mesures ultra-violettes fournies par l instrument satellitaire GOME 2 (également à bord du satellite MetOp) et les instruments au sol du réseau Brewer-Dobson mais également des mesures infrarouges (TES et AIRS). Les colonnes partielles sont, elles, comparées à des mesures de ballons sondes. Un autre volet de mes travaux de thèse consiste à préparer l assimilation des données IASI dans le modèle CHIMERE, en utilisant un Filtre de Kalman d Ensemble. Cette méthode permet d établir les covariances des erreurs du modèle à partir d un ensemble de différentes configurations du modèle. Dans ce contexte, un travail sur la construction d'un ensemble reflétant au mieux la réalité a été entrepris. La qualité de l'ensemble a été évaluée, dans la dimension verticale et en surface, à partir de différents outils, qui reposent tous sur des comparaisons aux observations.PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Global and local ozone measurements from the thermal infrared IASI/METOP sounder

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What IASI can tell us in the aftermath of the Hunga Tonga exceptional eruption

International audienc

Global and Local Ozone Measurements from the Thermal IASI Sounder for the Monitoring of Atmospheric Composition

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Global and local ozone measurements from the thermal infrared IASI sounder for the monitoring of atmospheric composition

http://smsc.cnes.fr/IASI/PDF/conf2/session8/Scannell.pdfInternational audienc

O₃ variability in the troposphere as observed by IASI over 2008-2016: Contribution of atmospheric chemistry and dynamics

International audienceWe analyze the ozone (O3) variability in the troposphere (from ground to 300 hPa) using eight years (January 2008 – March 2016) of O3 profile measurements provided by the Infrared Atmospheric Sounding Interferometer (IASI) onboard the MetOp satellite. The capability of IASI to monitor the year-to-year variability in that layer is examined first in terms of vertical sensitivity, a priori contribution and correlations in the deseasonalized anomalies with the upper layers. We present global patterns of the main geophysical drivers (e.g. solar flux - SF, Quasi-Biennial Oscillations - QBO, North Atlantic Oscillation - NAO, El Niño/Southern Oscillation - ENSO) of IASI O3 variations, obtained by applying appropriate annual and seasonal multivariate regression models on time series of spatially gridded averaged O3. The results show that the models are able to explain most of the O3 variability captured by IASI. Large O3 changes in the North Arctic/Euro-Atlantic sector and over the equatorial band are attributed to the NAO and the QBO effects, respectively. ENSO is modeled as the main contributor to the O3 variations in the tropical band where direct effects of warm and cool ENSO phases are highlighted with a clear tropical-extratropical gradient. A strong West-East gradient in the tropics is also found and likely reflects an indirect effect related to ENSO dry conditions. Finally, we also show that the ENSO perturbs the O3 variability far from the tropics into mid- and high latitudes where a significant 4-month time-lag in the response of O3 to ENSO is identified for the first time

O₃ variability in the troposphere from IASI observations in 2008-2015

International audienceWe present geographical patterns of ozone (O3) variability in the troposphere derived from 8 years of IASI observations (2008-2015). The instrument provides a unique dataset of global vertically-resolved O3 profiles with a twice daily global coverage and a fairly good vertical resolution in the troposphere allowing us to monitor the year-to-year variability in that layer. The retrievals are performed using the FORLI software, a fast radiative trans- fer model based on the optimal estimation method, set up for near real time and large scale processing of IASI data.Multivariate regressions which include important geophysical drivers of O3 variation (e.g. solar flux - SF, quasi biennial oscillations - QBO, El Niño/Southern Oscillation - ENSO, North Atlantic Oscillation-NAO) and a linear trend term have been performed on time series of spatially averaged O3 on spatial grids. The performances of the regression models (annual vs seasonal) and the effect of the spatial resolution are first investigated. The resulting covariates and trend spatial structures are then analyzed. Direct effects of NAO and of positive (or negatives) ENSO indexes measured during moderate to intense El Niño (or La Niña) episodes in 2009 and 2015 (or 2010) observed in the ozone columns in the tropics will be discussed. We will also focus on O3 trends over and downwind anthropogenic polluted areas characterized either by increased (e.g. over Asia) or decreased (e.g. over Europe and the US) O3 precursor emissions