Large-Scale monitoring of dry snow in High Mountain Asia (2015–2024) from Sentinel-1 SAR observations

Résumé fourni par la source

Dry-snow zones, the highest and coldest parts of a glacier where summer melt is absent, remain poorly constrained in High Mountain Asia (HMA) due to limited high-altitude observations. Here we present the first decadal, region-wide assessment of dry-snow distribution across HMA from 2015 to 2024 based on Sentinel-1 SAR observations. A physically guided approach combining SAR backscatter thresholds with an elevation constraint is used to delineate dry-snow zones. Dry snow is mainly confined to high-altitude western and southern regions, while largely absent elsewhere across HMA. Its extent shows strong interannual sensitivity to summer air temperature, weak correlation to precipitation, and positive associations with glacier mass balance across subregions. The consistency between SAR-derived dry-snow patterns and independent climatic and mass-balance signals indicates that this simple, physically based approach provides reliable large-scale estimates of accumulation-state conditions in data-sparse, high-elevation environments. Dry-snow extent therefore emerges as a sensitive and previously underexplored indicator of glacier–climate interactions, providing new observational constraints for future glacier-change projections.

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