Westward shift of Indian summer monsoon precipitation and heat wave frequency patterns over South Asia

Abstract

The phenomenon of climate change has significantly impacted weather patterns across the globe, particularly in South Asia. This study indicates a notable westward shift in precipitation and heat wave frequency over India, Pakistan and their adjacent regions. This shift is characterized by altered monsoon patterns, increased frequency of extreme weather events, and changing temperature regimes, which collectively pose challenges to water resources, cryosphere, agriculture, and public health. To comprehensively understand the dynamic nature of heat wave frequency, here we choose average vertical pressure velocity (ω), geopotential height, meridional wind vector and average temperature anomalies and heat wave frequency number of days meeting the criteria of at least three consecutive days above the 90th percentile. Our findings reveal a pronounced westward shift in heat wave frequency, particularly between June 1990 to August 2000, and from March 2000 to 2010. Additionally, the northwestern regions of India and Pakistan and eastern region (Myanmar) have experienced notable positive precipitation anomalies from 2000 to 2024, closely linked to Middle East warming. In contrast, negative precipitation anomalies over Tibet and the Himalayas threaten glacier and permafrost health. This finding suggests the upper atmospheric anticyclone or atmospheric blocking are a major drivers of Heat waves. In light of these extreme weather changes, advancing climate-resilient infrastructure is essential to mitigate risks and to ensure long-term environmental and socioeconomic stability.