Geospatial investigation of natural disaster through climatic parameters over the higher Himalayan region: a case study for Dharali Uttarkashi catastrophic event (2025)

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To evaluate the interdependent role in the regional climate system this study integrates ERA5-Land reanalysed hydrometeorological parameters (Precipitation, Moisture flux, Evapo-transpiration, Temperature, Surface-pressure, Wind, and Sea-level pressure) over the Indian Himalayan region. Long term (for year 1991–2025) Mean and Maximum Precipitation variability has been analysed to show the spatial and temporal aspects of precipitation variability. Spatial analysis showed that mean precipitation is higher in the south and south-central, and lower in north and northeast. Five year averaged seasonal precipitation for January–September months, examined to approach the extreme event and emphasize that precipitation variability is not uniform and is influenced by spatial gradients. The lead–lag regression of precipitation (PPT), moisture fluxes (MF) and evapotranspiration (EVAP) with the first principal component (PC1) techniques are applied. The lead–lag analysis suggested that the precipitation variability is associated with moisture transport and land-atmosphere exchanges, with a transition from weaker to stronger anomalies towards the peak phase (Lag = 0). Temperature anomalies show that the north is cooling (−0.2) and the south is warming (+0.15 to +0.2). The Lanczos band-pass filter has been applied to investigate the precipitation anomalies at specific timescales related to monsoon variability and wind convergence is strong at ±0.25 with a steady inflow of moisture to the southern slopes. Precipitation variability is strongly connected with temperature, pressure gradients, and moisture flow, according to lead–lag regression analysis. In order to identify unusual weather events, a spatial mapping of the monthly average precipitation and precipitation variance spectrum are analysed. Low-frequency (67–100 days) fluctuation predominates, according to frequency analysis, suggesting the impact of sub-seasonal characteristics and intra-seasonal oscillations. It has been demonstrated unequivocally that the topography and monsoon circulation pattern influence the regional variability of precipitation in the higher Himalayan region. Apart from this the study emphasises that the Dharali catastrophe is a cascade of hazards, resulting from the combination of flash floods and landslides triggered by heavy rainfall, due to high precipitation events.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.