Analysis of snow cover variability and spatial difference in the High Mountain Asia

The High Mountain Asia (HMA) is a prominent global mountain system characterized by an average altitude exceeding 4,000 m, intricate topography, and significant spatial variability in climatic conditions. Despite its importance, there has been a relative paucity of research focusing on the spatiotemporal variations of snow cover, key controlling factors, and variability within HMA sub-basins. This study aims to address this gap by extracting snow cover percentage (SCP) and snow cover days (SCD) data from MOD10A2 snow products, integrating these with precipitation (P) and temperature (T) data from ERA5. Our objective is to analyze the spatiotemporal distribution characteristics of snow cover and to use path analysis to elucidate the key climatic factors and spatial differences influencing snow cover changes. The findings indicate that, on a temporal scale, the overall SCP in HMA exhibited a declining trend from 2001 to 2021. Interannual variations in SCP across HMA sub-basins revealed a decreasing trend in the Pamir (PAM), Western Tibetan Plateau (WTS), Eastern Tibetan Plateau (ETS), Western Kunlun (WKL), Qilian Shan (QLS), and Himalaya (HDS) regions, while an increasing trend was observed in other areas. Spatially, 22.97% of the HMA regions experienced an increase in SCD, primarily in the Western Himalaya (WHL), Central Himalaya (CHL), and Southeastern Tibet (SET) regions. Conversely, 28.08% of the HMA regions showed a decrease in SCD, predominantly in the Eastern Himalaya (EHL), HDS, and WTS regions. Temperature (T) emerged as the primary influencing factor of SCD change in most HMA sub-basins. However, in the Eastern Kunlun (EKL) and WHL sub-basins, precipitation (P) was identified as the main driver of SCD change, affecting all elevation zones in these regions. Additionally, other climatic conditions can also impact snow cover beyond the primary controlling factor.