Aircraft‐Based Observations of Ozone‐Depleting Substances in the Upper Troposphere and Lower Stratosphere in and Above the Asian Summer Monsoon

Recent studies show that the Asian summer monsoon anticyclone (ASMA) transports emissions from rapidly industrializing nations in Asia into tropical upper troposphere. Here, we present a unique set of measurements on over 100 air samples collected multiple flights M55 Geophysica high altitude research aircraft Mediterranean, Nepal, and Northern India during summers 2016 2017 as part European Union project StratoClim. These were measured for 27 ozone-depleting substances (ODSs), many which enhanced above expected levels, including chlorinated very short-lived substances, dichloromethane (CH2Cl2), 1,2-dichloroethane (CH2ClCH2Cl), chloroform (CHCl3). CH2Cl2 mixing ratios tropopause region 65–136 parts per trillion (ppt) comparison to previous estimates layer 30–44 ppt 2013–2014. Backward trajectories, calculated with trajectory module chemistry-transport model CLaMS driven by ERA5 reanalysis, indicate possible source regions South Asia. We derived total equivalent chlorine (ECl), effective stratospheric (EESC) found these quantities substantially higher than literature. EESC at mean age-of-air 3 years based was 1,861–1,872 previously estimated 1,646 ppt. Our findings ASMA larger long-lived ODSs troposphere lower stratosphere, likely leading an impact ozone layer.