Contributions of Overshooting Convection Over the South Asian Monsoon Region to Stratospheric Water Vapor

Abstract

Stratospheric water vapor content impacts the Earth's radiative budget as well as atmospheric chemistry, affecting surface temperature. Deep convection over the Indian region during the summer monsoon can form cirrus clouds at the tropical tropopause layer that can affect the moisture content in the stratosphere. In order to improve understanding of processes controlling stratospheric water vapor, I use Cloud-Aerosol LIDAR and Infrared Pathfinder Satellite Observation (CALIPSO) data and surface reanalysis precipitation and subcloud moist static entropy (MSE) products to study and compare cloud formation above the Indian region during the active monsoon period as well as spatially, over the marine Bay of Bengal and Himalayan south slopes. It was hypothesized that higher convection would be found over the Himalayan South Slopes and that over 50\% of thin cirrus clouds in this region would have convective origins. The Tropical Tropopause Layer (TTL) cirrus observations are put in context with rainfall and atmospheric boundary layer moist entropy data, but attribution and source classification was impeded by the much coarser horizontal and temporal resolution of these supplementary data. However, case studies supporting base relationships such as convective cloud cores associated with intense precipitation and deep convection over the Himalayan South Slopes were found, confirming part of the hypothesis. Overall, the region remains undetermined in its contributions to TTL cirrus and stratospheric water vapor balance, but convective case studies and frequency of high-altitude clouds indicate that further research in the South Asian Monsoon region will yield further insights into both processes.