Impacts of the Indian Summer Monsoon on the southern boundary water vapor transport and precipitation over the Tibetan Plateau

Abstract

Abstract Water vapor transport plays a significant role in maintaining the water cycle over the Tibetan Plateau (TP). This study investigates the characteristics of water vapor transport across TP southern boundaries and its impacts on TP precipitation during the Indian summer monsoon (ISM) season from 2000 to 2019. The southern boundary is subdivided into four sub-boundaries (boundaries 7, 8, 9, and 10) from the east to the west. Water vapor transports of boundaries 7, 8, and 9 are mainly affected by ISM, while mid-latitude westerlies dominate the water vapor transport of boundary 10. The results show that the PCR precipitation concentrated over the center TP in both ISM strong and weak months is smaller in the ISM weak months than the normal months for most of the day, while it is larger in the ISM strong months than the normal months. The PCR precipitation correlates positively with the water vapor transport across boundary 10 in both the ISM strong and weak months. Although there is water vapor transport across boundary 7 in both the ISM weak and strong months, the water vapor can hardly be brought to PCR. The correlation between the PCR precipitation and the water vapor from the BOB and the Arabian Sea is more intense in ISM strong months than in ISM weak months. Conversely, the water vapor transport efficiency is low in ISM strong months due to a cyclonic circulation over northern India, preventing water vapor transport from reaching the TP directly.