Analysis of Temporal and Spatial Variations in Extreme Precipitation over Kerala

Kerala, an ecologically sensitive state in southwestern India, is increasingly vulnerable to rainfall-induced disasters such as floods and landslides. This study analysed 124 years (1901–2024) of high-resolution daily rainfall data from the India Meteorological Department (IMD) to examine spatial and temporal trends across Kerala. The analysis assessed changes in rainy days and the frequency of heavy (HRF), very heavy (VHRF), and extremely heavy rainfall (EHRF) events, along with shifts in the onset of the southwest monsoon (SWM) and northeast monsoon (NEM) and rainfall irregularity using the Precipitation Concentration Index (PCI). Results revealed strong spatial heterogeneity: northern Kerala receives higher SWM rainfall (~3000 mm), while southern regions experience more intense rainfall during the NEM and winter seasons. Breakpoint analysis indicated a recent change in NEM rainfall around 2020, with a steep increase in slope from -0.527 to 23.048. High PCI values (11–21) in northern and central-western regions reflect strong rainfall concentration and elevated flood risks. Rainy days and EHRF events increased during the SWM and summer, while declines during the NEM and winter could affect water availability and winter cropping. Long-term projections suggest the SWM may advance toward May and the NEM extend into late October. These changing rainfall dynamics hold significant implications for agriculture, water management, and climate adaptation planning, emphasizing the need for location-specific strategies.