Change in Extreme Precipitation Over Indochina Under Climate Change From a Lagrangian Perspective of Water Vapor

Zelun Cheng,Jie Yan,Zuowei Xie,Cholaw Bueh,Wei Tang,Yuanfa Gong

doi:10.3389/feart.2021.758664

Abstract

The process of global warming has humidified the atmosphere and increased the occurrence of extreme-precipitation events over the Indochina Peninsula, which lies in the transition region from the South Asian monsoon to the East Asian monsoon. The annual occurrence number of days of extreme precipitation over the Indochina Peninsula exhibits a significant change in 2003, with an abnormally higher occurrence number during the period 2003–2015 than that during 1951–2002. The extreme precipitation and such decadal change are contributed by more moisture sources associated with an enhanced dipole circulation over the Indian Ocean, which could be linked to the Pacific Decadal Oscillation. The daily large-scale meteorological pattern directly associated with extreme precipitation is characterized by an enhanced dipole of the typical summer monsoon pattern, with a zonally elongated Mascarene high and a deepened monsoon trough from northern India to the South China Sea. Such an intensified dipole provides two major channels of water vapor: one along the low-level westerly jet over the Indian Ocean and the other along the gyre of monsoon trough over the South China Sea. Compared with that during the period 1951–2002, the dipole is enhanced from northern India to the Indian Ocean and weakened over the Indochina Peninsula during the period 2003–2015. Although the Lagrangian analysis shows that the trajectory of air masses is displaced southward to the Indian Ocean, the intensified low-level westerly jet increases the evaporation of water from the ocean and thus not only enhances the water channel over the Indian Ocean but also yields a parallel water channel over the Bay of Bengal. In contrast, in spite of the increased trajectory density of air masses over the South China Sea, the lingering of air mass suppresses the evaporation of water and thus provides a declined contribution to the extreme precipitation during 2003–2015.

Highlights

Global warming increases the frequency and intensity of extremeprecipitation events (Alexander et al, 2006; Zhang et al, 2020)
This study focuses on the change in extreme precipitation between the two subperiods of 1951–2002 and 2003–2015 in terms of changes of circulation pattern and water vapor transport from the Lagrangian perspective
The analysis with the Lagrangian tool shows that these two flows constitute two major water vapor channels: one along the low-level westerly jet over the Indian Ocean and the other from the South China Sea

Summary

Introduction

Global warming increases the frequency and intensity of extremeprecipitation events (Alexander et al, 2006; Zhang et al, 2020). The intensification of extreme precipitation is principally caused by enhancement of atmospheric moisture content, which plays an important role in the global water cycle and climate system (Bengtsson, 2010). Changes in the intensity and pathways of moisture transport lead to variabilities in rain belts and patterns (Zhou et al, 2001; Huang et al, 2011). The Indochina Peninsula is located in the Asian monsoon region, where there is abundant moisture content and a greater vulnerability to climate change (Ge et al, 2017). Investigating the moisture change for extreme precipitation over the Indochina Peninsula against the background of climate change is an important topic for the atmospheric water cycle and could provide guidance for regional water resources management and natural disaster prediction (Christensen and Christense, 2003)

Results

Discussion

Conclusion