| Summary: | International audience In this study, we present geographical patterns of ozone (O 3 ) variability in the troposphere and the stratosphere derived from 9 years of IASI observations (2008-2017). The instrument provides a unique dataset of global vertically-resolved O 3 profiles with a twice daily global coverage and a fairly good vertical resolution in both the troposphere and the stratosphere, allowing to monitor the year-to-year variability in these layers. The retrievals are performed using the FORLI software, a fast radiative transfer 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 O 3 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 gridded averaged O 3 . The performance of the regression models for the different altitude layers is evaluated in terms of the representativeness of the fitted model and explanatory variables. The spatial structures of the resulting covariates and trends are then analyzed. In particular, we will also focus on O 3 trends observed in the upper stratosphere, which possibly point out a recovery of upper stratospheric ozone, and in the troposphere over and downwind anthropogenic polluted areas characterized either by increased (e.g. over Asia) or decreased (e.g. over Europe and the US) O 3 precursor emissions. FORLI O 3 -CO correlations patterns in the troposphere will also be discussed to evaluate the continental influence on tropospheric O 3 trends.
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