Guwahati: Northeast India is experiencing both heavier single-day rainfall and longer dry spells, according to a new study that examined weather patterns across the region from 1971 to 2022. The study covers Assam, Meghalaya, Nagaland, Manipur, Mizoram, Tripura, Arunachal Pradesh and Sikkim.
Titled ‘Evolution of Climate Extremes Over the Indian Subcontinent Using a Revised CEI’, the study was published in the peer-reviewed International Journal of Climatology. It was conducted by scientists from the India Meteorological Department (IMD) and the National Centre for Medium Range Weather Forecasting (NCMRWF).
The researchers combined seven weather hazards, including daytime heat, humid heat, heatwave severity and drought, into a single India Climate Extremes Index. The index was developed using 52 years of IMD observations, with trends tested using the Mann-Kendall method.
The study found that the northeast is the only region in India showing a clear and statistically significant rise in extreme one-day rainfall.
The authors linked the increase to a warming Bay of Bengal, higher atmospheric moisture and the region’s complex terrain.
At the same time, the study found that dry spells and drought are becoming more frequent in the northeast.
The authors said the combination indicates increasing instability in the monsoon over the region rather than a simple shift towards wetter or drier conditions.
“The northeast is the one region swinging between extremes, heavier single-day downpours on one side and longer dry spells on the other. That combination points to a more unstable monsoon, and it calls for both flood preparedness and drought planning,” said M. Rajeevan, co-author of the study at Atria University, Bengaluru.
Thota Mohan, lead author of the study at the National Centre for Medium Range Weather Forecasting, said the northeast is the only part of the country showing a clear rise in short, intense one-day rainfall while dry spells are also lengthening.
The study recommends strengthening flood preparedness and rainfall-variability management in the northeast.
It calls for a cross-sectoral response covering agriculture, water management, health and infrastructure.
The researchers also recommended finer-scale monitoring, noting that regional averages can mask localised extremes that contribute to flood and drought risks.
The authors proposed the India Climate Extremes Index as an operational tool that agencies can use each year to track areas where climate-related stress is building.