Role of deep convection and dynamics on the tracer distribution in the upper troposphere and lower stratosphere region during active and break phases of the Asian summer monsoon

The Asian Summer Monsoon (ASM) exhibit different modes of variability in which the active and break phases is one of the most prominent intraseasonal scale variability of the ASM. The shift in convective centres to more polluted regions coupled with the associated circulation features during these phases results in a redistribution of trace species in the upper troposphere and lower stratosphere (UTLS) region. Apropos to this, this study presents a quantitative assessment of the variability in the spatial distribution of ozone, carbon monoxide (CO) and water vapour (H 2 O) in the UTLS during the active and break phase of ASM with respect to the seasonal mean background using fifteen years (2005–2019) of Aura-MLS observations in conjunction with reanalysis data sets, cloud-top brightness temperatures and trajectory analysis. These 15-years of data is used to make composite maps of tracer anomalies to investigate the varying influence of monsoon convection, transport and ASMA dynamics in the UTLS region during the active/break phase. This study shows that, while the distribution of trace species during both phases is determined by the combined role of convection and transport in the upper troposphere, changes in ASMA modes, transport and tropopause dynamics during the active/break phases controls the spatial pattern of both tropospheric and stratospheric species near the tropopause level.