An observational perspective on extreme precipitation indices over the mountainous regions of Northwest Himalaya

Abstract

The Northwest Himalaya region is highly susceptible to extreme rainfall events due to its steep topography and complex climatic variability, which can trigger significant hydro-meteorological hazards, including heavy snowfall, hailstorms, floods, and droughts. The erratic precipitation patterns, both in the short and long term, exacerbate these hazards. Furthermore, climate change is amplifying the frequency and intensity of extreme weather events, thereby increasing the vulnerability of the region and posing substantial challenges for infrastructure resilience, agricultural sustainability, and effective disaster management. This study utilizes the High Asia Refined Analysis version 2 dataset (HARv2), a high-resolution (10 km) WRF model output, spanning 1981–2020, to analyze precipitation trends across three sub-regions — Jammu & Kashmir (JK), Himachal Pradesh (HP), and Uttarakhand (UK) — validated against IMD and IMDAA datasets. All extreme precipitation indices as defined by the Expert Team on Climate Change Detection and Indices (ETCCDI) have been used for the study. ERA5 and HARv2 derived VIMT analysis is done for large-scale moisture influx understanding, and the role of ENSO in driving moisture transport is examined. JK exhibits the most pronounced drying signal, with statistically significant declines across multiple precipitation indices, while increasing CDD over both JK and HP indicates growing drought risk. UK shows no significant trends, reflecting the dominant role of orographic processes in its precipitation regime. A distinct spatial gradient in precipitation-generating mechanisms is identified — from synoptic-dynamic control over JK to orographic dominance over UK, with HP representing a transitional regime. With multiple diagnostic variables evaluated, it is concluded that moisture alone does not explain precipitation extremes in the NWH, and that orographic uplift and synoptic-scale disturbances are equally important drivers. The findings highlight the need for targeted climate change mitigation strategies and region-specific resource allocation to protect the vulnerable Himalayan region.