How Well do Global Snow Products Characterize Snow Storage in High Mountain Asia?

Accurate characterization of peak snow water storage in High Mountain Asia (HMA) is essential for assessing the water supply to over 1 billion downstream residents. Currently, such characterization still relies on modeling due to measurement scarcity. Here, eight global snow products were examined over HMA using a newly developed High Mountain Asia Snow Reanalysis (HMASR) data set as a reference. The focus of intercomparison was on peak annual snow storage, the first‐order determinant of warm‐season water availability in snow‐dominated basins. Across eight products the climatological peak storage over HMA was found to be 161 ± 102 km3 with an average 33% underestimation relative to HMASR. The inter‐product variability in cumulative snowfall (335 ± 148 km3) explains the majority (>80%) of peak snow storage uncertainty, while significant accumulation‐season snowfall loss to ablation (51% ± 9%) also reveals the critical role of ablation processes on peak snow storage. Plain Language Summary Peak snow storage is important for summer and fall water availability in snow‐dominated regions. Here, we evaluated the estimates of peak snow storage over High Mountain Asia (HMA) from eight global snow products with respect to the newly developed High Mountain Asia Snow Reanalysis (HMASR). The results suggest a large uncertainty and general underestimation (33%) in HMA‐wide peak snow storage estimates across the global snow products, when compared to the reference HMASR. Inter‐product snowfall variability among global snow products explains most of their peak snow storage uncertainty (over 80%). Significant snow ablation loss during the accumulation season (∼50% of snowfall inputs) is also critical in contributing to the peak snow storage variations. Key Points Existing snow products generally underestimate peak snow storage in High Mountain Asia compared with a novel snow reanalysis data set Large inter‐product variability in accumulation‐season snowfall explains most of the uncertainty in peak snow storage Accumulation‐season ablation plays a significant role in peak snow storage uncertainty and deserves more attention in future studies