Seasonal and interannual variations of water vapor in the upper troposphere and lower stratosphere over the Asian Summer Monsoon region- in perspective of the tropopause and ocean-atmosphere interactions

Abstract

In this study, we examine distributions of water vapor in the upper troposphere and lower stratosphere (UTLS) over the Asian Summer Monsoon (ASM) anticyclone during summer using thirteen years of Aura Microwave Limb Sounder observations. We also present the role of tropical tropopause and ocean-atmosphere interactions in controlling the UTLS water vapor over the ASM anticyclone region. Water vapor accumulated inside the central part of ASM anticyclone is primarily transported from the low-latitude oceanic region and very less amount of water vapor is pumped directly from the lower to the upper troposphere. It is concluded water vapor in the UTLS region inside the central part of ASM anticyclone is mostly controlled by horizontal advection and very less from the local process and tropopause temperature in both summer and winter. The tropopause altitude is highest, and the pressure is lowest inside the central part of ASM anticyclone as compared to the other tropical ASM regions during summer. In addition, there is an increase of 1–1.3 ppmb water vapor along with the warm tropopause in the UTLS region during El-Niño events over the entire ASM region, however, more water vapor is observed over the southern (tropical) part of ASM region. These observations help in understanding the controlling factor for the distribution of water vapor in the UTLS water vapor in different seasons.