Decrease in tropospheric O3 levels of the Northern Hemisphere observed by IASI

Abstract : In this study, we describe the recent changes in the tropospheric ozone (O3) columns (TOCs) measured by the Infrared Atmospheric Sounding Interferometer (IASI) onboard the Metop satellite during the first 9 years of the IASI operation (January 2008 to May 2017). Using appropriate multivariate regression methods, we discriminate significant linear trends from other sources of O3 variations captured by IASI. The geographical patterns of the adjusted O3 trends are provided and discussed on the global scale. Given the large contribution of the natural variability in comparison with that of the trend (25–85 % vs 15–50 %, respectively) to the total O3 variations, we estimate that additional years of IASI measurements are generally required to detect the estimated O3 trends with a high precision. Globally, additional 6 months to 6 years of measurements, depending on the regions and the seasons, are needed to detect a trend of  |5| DU/decade. An exception is interestingly found during summer in the mid-high latitudes of the North Hemisphere (N.H.; ~ 40° N–75° N) where the large absolute fitted trend values (~ |0.5| DU/yr on average) combined with the small model residuals (~ 10 %) allow the detection of a band-like pattern of significant negative trends. This finding supports the reported decrease in O3 precursor emissions in recent years, especially in Europe and US. The influence of continental pollution on that latitudinal band is further investigated and supported by the analysis of the O3–CO relationship (in terms of correlation coefficient, regression slope and covariance) that we found to be the strongest at the northern mid-latitudes in summer.
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Article dans une revue
Atmospheric Chemistry and Physics Discussions, European Geosciences Union, In press, pp.(Under Review)
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Contributeur : Catherine Cardon <>
Soumis le : jeudi 23 novembre 2017 - 17:30:48
Dernière modification le : mercredi 21 mars 2018 - 18:58:21

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  • HAL Id : insu-01646776, version 1

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Catherine Wespes, Daniel Hurtmans, Cathy Clerbaux, Anne Boynard, Pierre-François Coheur. Decrease in tropospheric O3 levels of the Northern Hemisphere observed by IASI. Atmospheric Chemistry and Physics Discussions, European Geosciences Union, In press, pp.(Under Review). 〈insu-01646776〉

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