Heatwaves, an extreme temperature events, have gained copious attention. This study conducts a comprehensive analysis of heatwaves (HWs) over four decades from 1980 to 2021. Empirical Orthogonal Function (EOF) analysis is used to identify the dominant spatial pattern in maximum temperature (Tmax) variability across the Indian region. The analysis identifies four significant regions: Central Northeast (CNE), South Central (SC), Northwest (NW) and Southeast (SE) with distinct temperature pattern. Subsequently, the spatial and temporal variations in HWs, indicate an increase in frequency, severity, and duration over the past four decades. Temporal trend shows an increase in HW frequency and duration across most of the regions over a 42-year period. To comprehend the underlying mechanism of HW events, study investigates various meteorological parameters observed during HW days. Maximum temperature anomalies increase by 4–5 °C, accompanied by positive surface solar radiation (SSR) of 10–20 W/m2 along with lower mean sea level pressure (mslp), and a reduction in relative humidity (RH) of − 6% to -15%. Geopotential height at different pressure level highlight anticyclonic circulation pattern associated with temperature extremes. Additionally, backward trajectory analysis is used to delineate distinct source regions and atmospheric processes linked with HW events in different parts of India. A detailed analysis of spatial and temporal variation of HWs and their associated meteorological factors contribute in development of effective mitigation and adaptation strategies. Graphical Abstract The graphical abstract depicts the spatial and temporal variability of heat waves (HWs) over India from 1980 to 2021. HW days were analysed using the India Meteorological Department (IMD) and MERRA-2 reanalysis datasets. Atmospheric drivers like increased surface solar radiation, rising surface temperature, and relative humidity primarily intensify the HW condition. Furthermore, the formation of a heat dome, associated with anticyclonic condition and high-pressure system, is a crucial mechanism promoting prolonged period of high temperature. Empirical Orthogonal Function (EOF) analysis identifies four dominant modes of HW variability over North West (NW), Central North East (CNE), South Central (SC), and Southeast (SE) India. These distinct patterns help to understand the regional and spatial variability of HW events. Further, the HW criteria based on daily maximum temperature (Tmax) exceeding the 90th percentile for at least six consecutive days identified the significant HW days. Lastly, backward trajectory analysis using the NOAA HYSPLIT model traces the origins of air masses for the intrusion of hot and dry air during HW events.

Heatwaves Over the Indian Subcontinent: Mechanisms, Variability and Sources

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发表日期：

2025年6月4日

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Priyanshu Gupta,
Aditya Kumar Dubey,
R. Bhatla,
Swagata Payra,
Sunita Verma

摘要

Heatwaves, an extreme temperature events, have gained copious attention. This study conducts a comprehensive analysis of heatwaves (HWs) over four decades from 1980 to 2021. Empirical Orthogonal Function (EOF) analysis is used to identify the dominant spatial pattern in maximum temperature (T_max) variability across the Indian region. The analysis identifies four significant regions: Central Northeast (CNE), South Central (SC), Northwest (NW) and Southeast (SE) with distinct temperature pattern. Subsequently, the spatial and temporal variations in HWs, indicate an increase in frequency, severity, and duration over the past four decades. Temporal trend shows an increase in HW frequency and duration across most of the regions over a 42-year period. To comprehend the underlying mechanism of HW events, study investigates various meteorological parameters observed during HW days. Maximum temperature anomalies increase by 4–5 °C, accompanied by positive surface solar radiation (SSR) of 10–20 W/m² along with lower mean sea level pressure (mslp), and a reduction in relative humidity (RH) of − 6% to -15%. Geopotential height at different pressure level highlight anticyclonic circulation pattern associated with temperature extremes. Additionally, backward trajectory analysis is used to delineate distinct source regions and atmospheric processes linked with HW events in different parts of India. A detailed analysis of spatial and temporal variation of HWs and their associated meteorological factors contribute in development of effective mitigation and adaptation strategies.

Graphical Abstract

The graphical abstract depicts the spatial and temporal variability of heat waves (HWs) over India from 1980 to 2021. HW days were analysed using the India Meteorological Department (IMD) and MERRA-2 reanalysis datasets. Atmospheric drivers like increased surface solar radiation, rising surface temperature, and relative humidity primarily intensify the HW condition. Furthermore, the formation of a heat dome, associated with anticyclonic condition and high-pressure system, is a crucial mechanism promoting prolonged period of high temperature. Empirical Orthogonal Function (EOF) analysis identifies four dominant modes of HW variability over North West (NW), Central North East (CNE), South Central (SC), and Southeast (SE) India. These distinct patterns help to understand the regional and spatial variability of HW events. Further, the HW criteria based on daily maximum temperature (T_max) exceeding the 90th percentile for at least six consecutive days identified the significant HW days. Lastly, backward trajectory analysis using the NOAA HYSPLIT model traces the origins of air masses for the intrusion of hot and dry air during HW events.