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During the Asian summer monsoon, the circulation in the uppertroposphere/lower stratosphere (UTLS) is dominated by the Asian monsoonanticyclone (AMA). Pollutants convectively uplifted to the upper troposphereare trapped within this anticyclonic circulation that extends from thePacific Ocean to the Eastern Mediterranean basin. Among the upliftedpollutants are ozone (O3) and its precursors, such as carbon monoxide (CO)and nitrogen oxides (NOx). Many studies based on global modeling andsatellite data have documented the source regions and transport pathways ofprimary pollutants (CO, HCN) into the AMA. Here, we aim to quantify the O3budget by taking into consideration anthropogenic and natural sources. Wefirst use CO and O3 data from the MetOp-A/IASI sensor to document theirtropospheric distributions over Asia, taking advantage of the usefulinformation they provide on the vertical dimension. These satellite data areused together with MOZAIC tropospheric profiles recorded in India to validatethe distributions simulated by the global GEOS-Chem chemistry transportmodel. Over the Asian region, UTLS monthly CO and O3 distributions fromIASI and GEOS-Chem display the same large-scale features. UTLS CO columnsfrom GEOS-Chem are in agreement with IASI, with a low bias of11 ± 9 % and a correlation coefficient of 0.70. For O3, the modelunderestimates IASI UTLS columns over Asia by 14 ± 26 % but thecorrelation between both is high (0.94). GEOS-Chem is further used toquantify the CO and O3 budget through sensitivity simulations. For CO,these simulations confirm that South Asian anthropogenic emissions have amore important impact on enhanced concentrations within the AMA(∼  25 ppbv) than East Asian emissions (∼  10 ppbv). Thecorrelation between enhanced emissions over the Indo-Gangetic Plain andmonsoon deep convection is responsible for this larger impact. Consistently,South Asian anthropogenic NOx emissions also play a larger role inproducing O3 within the AMA (∼  8 ppbv) than East Asian emissions(∼  5 ppbv), but Asian lightning-produced NOx is responsible for thelargest O3 production (10–14 ppbv). Stratosphere-to-troposphereexchanges are also important in transporting O3 in the upper part ofthe AMA

Upper-tropospheric CO and O&lt;sub&gt;3&lt;/sub&gt; budget during the Asian summer monsoon

Upper-tropospheric CO and O<sub>3</sub> budget during the Asian summer monsoon