Impacts of An Overshooting Deep Convection Process over Subtropical Asian Monsoon Region on the Variation of the Lower Stratospheric Atmospheric Composition

The rapid transport associated with overshooting deep convection is essential for the summertime water vapor maxima in the lower stratosphere over the Asian monsoon region. However, the impacts of overshooting deep convection over the subtropical Asian monsoon region on the distribution of the lower stratospheric atmospheric composition have not been fully addressed. In this study, the authors use CloudSat and Aura Microwave Limb Sounder satellite data to investigate the characteristics of overshooting deep convections in Wuhan rainstorm during 2016. The concentrations of water vapor (H₂O), ice water content (IWC), and ozone (O₃) in the upper troposphere/lower stratosphere during overshooting deep convections are analyzed. Overshooting deep convection case, which occurred at 0500 UTC on 4 July 2016, considerably reduced the ozone mixing ratio near the tropopause. Specifically, it led to a 32.53% decrease in the climatological mean ozone mixing ratio. The overshooting convection is also found to enhance the moisture content in the lower subtropical stratosphere, and this hydrating effect has two mechanisms: that induced by ice particle evaporation and that by the convective moisture flux itself. Overshooting convection results in a greater change in the moisture (about 98.15% increase of the climatology) than in the ozone. Our study results indicate that the local overshooting convections over the subtropical Asian monsoon region in boreal summer are important factors in the transport of water vapor from the troposphere into the low stratosphere.