Kolkata: A new study by researchers from IIT Kharagpur has identified a strong “precipitation dipole” across the Himalayas: when the central and eastern Himalayas face extreme rain or snow, the western Himalayas tend to remain relatively dry — and vice versa.The finding, published in the Quarterly Journal of the Royal Meteorological Society, suggests early warning systems must be more location-specific, as a system effective for one Himalayan region may not work for another.“Extreme precipitation can trigger floods, landslides, glacial lake outburst floods and other cascading hazards. The new framework can help identify which weather regime is developing, where moisture is moving, and which part of the Himalayas may face extreme precipitation,” said Priya Bharati, lead author of the study.Researchers from IIT Kharagpur’s Centre for Ocean, River, Atmosphere and Land Sciences (CORAL) and the University of Reading analysed 6,102 extreme precipitation events across the Himalayas between 1979 and 2023, identifying six recurring large-scale weather patterns — or “regimes” — linked to extreme precipitation across different parts of the range.Four regimes are linked to the monsoon: Bay of Bengal low-pressure systems, Arabian Sea low-pressure systems, monsoon-break conditions, and Western Disturbances interacting with the monsoon.The Karakoram, western Himalayas, and northwestern central Himalayas are more affected by winter and spring Western Disturbances; the central and eastern Himalayas by summer monsoon systems.The study connects these regimes with larger climate signals — the North Atlantic Oscillation, subtropical jet, Madden-Julian Oscillation, and Western Pacific Subtropical High — which could help assess risks days to weeks in advance.“The next step is to link atmospheric regime to precipitation, river response, slope instability and ultimately potential impacts,” said Prof Pranab Deb, co-author.
