Declining snowfall fraction in the alpine regions, Central Asia

In a warming climate, precipitation (P) is less likely to occur as snowfall (S). Change in the snowfall fraction (S/P) is currently assumed not only influences the accumulation and ablation of glaciers, but also influences the streamflow and water resources significantly in mountainous regions. However, until now, most studies have focused on precipitation magnitude and its frequency changes, while seasonal shifts in precipitation types have been mostly neglected. This paper employs the threshold temperature method in combination with multi-source dataset (APHRODITE, CPC and meteorological stations) analysis to determine snowfall proportions in precipitation in the Tienshan Mountains, Central Asia, during 1960-2017. The results indicated that temperature-induced precipitation shifting from snow to rain. The S/P experienced an overall declining trend, increasing at a rate of 0.6%/decade prior to the mid-1990s, followed by a downward trend at a rate of -0.5%/decade. The S/P decreased mainly at low and middle altitudes (between 1500 and 3500 m). At higher altitudes (over 3500 m), the magnitudes of the decreased S/P ratios were small or even increased due to the temperature always being below freezing. Decreases in S/P are always associated with decreases in annual streamflow in the glacier/snow melt recharged rivers.