资源环境科技发展态势分析平台

In this study, we describe the recent changes in the tropospheric ozone (O-3) columns measured by the Infrared Atmospheric Sounding Interferometer (IASI), onboard the Metop satellite, during the first 9 years of operation (January 2008 to May 2017). Using appropriate multivariate regression methods, we differentiate significant linear trends from other sources of O-3 variations captured by IASI. The geographical patterns of the adjusted O-3 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 O-3 variations, we estimate that additional years of IASI measurements are generally required to detect the estimated O-3 trends with 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 vertical bar 5 vertical bar DU decade(-1). An exception is interestingly found during summer at midand high latitudes of the Northern Hemisphere (NH; similar to 40 to similar to 75 degrees N), where the large absolute fitted trend values (similar to vertical bar 0.5 vertical bar DU yr(-1) on average) combined with the small model residuals (similar to 10 %) allow for detection of a band-like pattern of significant negative trends. Despite no consensus in terms of tropospheric O-3 trends having been reached from the available independent datasets (UV or IR satellites, O-3 sondes, aircrafts, ground-based measurements, etc.) for the reasons that are discussed in the text, this finding is consistent with the reported decrease in O-3 precursor emissions in recent years, especially in Europe and USA. The influence of continental pollution on that latitudinal band is further investigated and supported by the analysis of the O-3-CO relationship (in terms of correlation coefficient, regression slope and covariance) that we found to be the strongest at northern midlatitudes in summer.