Abstract We examine seasonal and monthly rainfall variability for India and its meteorological homogeneous regions based on the India Meteorological Department (IMD) gridded rainfall data for the satellite era (1979–2023). While analysing interannual variability during contrasting monsoon years, India’s rainfall as a whole showed less variability, however, significant regional variability is noticed in rainfall patterns. Analysis of contrasting monsoon years that experienced excess and deficit seasonal rainfall over the study period reveals that along large-ascale with the July and September consistently emerge as the most impacted months for All India, as well as for the West Central India and Northwest Indian regions. Among the examined scenarios, Northwest India exhibits the most pronounced effects, whereas the North East Indian region displays an out-of-phase pattern compared to the other homogeneous regions. Monthly variations in rainfall patterns across homogeneous regions during contrasting years associated with large-scale climate drivers such as the El-Niño Southern Oscillation confirm that July and September stand out as evolving and critical months influencing overall rainfall patterns, with notable variations in precipitation intensity across different regions. Pre to post 20th century period (1979–2000 and 2001–2023), we observed an increase in rainfall of around 15% over Northwest India. Moreover, West Central India, and South Peninsular India noticed an increase in rainfall of around 4%, whereas 8–10% decrease in rainfall is observed over Central Northeast India and Northeast India. Understanding the response of homogeneous regional rainfall in the recent decades on seasonal and monthly scales has implications for better forecasting and planning effective water management and agricultural strategies amidst a changing climate. Research Highlights <UnorderedList Mark="Bullet"> <ItemContent> Our findings offer important new insights into regional responses to seasonal monsoon variability, particularly during excess and deficit years. July and September emerge as key months exerting strong influence on seasonal rainfall totals, with pronounced regional variations in both the timing and intensity of precipitation. </ItemContent> <ItemContent> The teleconnection between Indian summer monsoon rainfall and ENSO underscores the system’s complexity. Our results reveal a growing dominance of local and regional forcings in recent decades, while the classic La Niña-enhanced rainfall association persists in most regions. Distinct anomalous patterns in Northeast India (NEI) and Central Northeast India (CNEI) reflect unique regional responses to these evolving climatic interactions. </ItemContent> <ItemContent> Significant regional contrasts in Indian monsoon rainfall patterns have emerged between the periods 1979–2000 and 2001–2023. Rainfall increased by approximately 15% in Northwest India (NWI) and by about 4% in West Central India (WCI) and South Peninsular India (SPI), while it declined by 8–10% in Central Northeast India (CNEI) and Northeast India (NEI). </ItemContent> </UnorderedList>

Indian homogeneous regional rainfall variability in recent decades

期刊论文
发表日期：

2026年7月18日

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Akshay Kulkarni,
P V S Raju,
Archana Sagalgile,
Bhupendra Bahadur Singh

摘要

Abstract

We examine seasonal and monthly rainfall variability for India and its meteorological homogeneous regions based on the India Meteorological Department (IMD) gridded rainfall data for the satellite era (1979–2023). While analysing interannual variability during contrasting monsoon years, India’s rainfall as a whole showed less variability, however, significant regional variability is noticed in rainfall patterns. Analysis of contrasting monsoon years that experienced excess and deficit seasonal rainfall over the study period reveals that along large-ascale with the July and September consistently emerge as the most impacted months for All India, as well as for the West Central India and Northwest Indian regions. Among the examined scenarios, Northwest India exhibits the most pronounced effects, whereas the North East Indian region displays an out-of-phase pattern compared to the other homogeneous regions. Monthly variations in rainfall patterns across homogeneous regions during contrasting years associated with large-scale climate drivers such as the El-Niño Southern Oscillation confirm that July and September stand out as evolving and critical months influencing overall rainfall patterns, with notable variations in precipitation intensity across different regions. Pre to post 20th century period (1979–2000 and 2001–2023), we observed an increase in rainfall of around 15% over Northwest India. Moreover, West Central India, and South Peninsular India noticed an increase in rainfall of around 4%, whereas 8–10% decrease in rainfall is observed over Central Northeast India and Northeast India. Understanding the response of homogeneous regional rainfall in the recent decades on seasonal and monthly scales has implications for better forecasting and planning effective water management and agricultural strategies amidst a changing climate.

Research Highlights

Our findings offer important new insights into regional responses to seasonal monsoon variability, particularly during excess and deficit years. July and September emerge as key months exerting strong influence on seasonal rainfall totals, with pronounced regional variations in both the timing and intensity of precipitation.

The teleconnection between Indian summer monsoon rainfall and ENSO underscores the system’s complexity. Our results reveal a growing dominance of local and regional forcings in recent decades, while the classic La Niña-enhanced rainfall association persists in most regions. Distinct anomalous patterns in Northeast India (NEI) and Central Northeast India (CNEI) reflect unique regional responses to these evolving climatic interactions.

Significant regional contrasts in Indian monsoon rainfall patterns have emerged between the periods 1979–2000 and 2001–2023. Rainfall increased by approximately 15% in Northwest India (NWI) and by about 4% in West Central India (WCI) and South Peninsular India (SPI), while it declined by 8–10% in Central Northeast India (CNEI) and Northeast India (NEI).