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The accumulation and ablation processes of seasonal snow significantly affect the land surface phenology in a mountainous ecosystem. However, the ability of snow to regulate the alpine land surface phenology in the arid regions is not well described in the context of climate change. The impact of snowpack changes on land surface phenology and its driving factors were investigated in the Tianshan Mountains using the land surface phenology metrics derived from satellited products and a snow dataset from downscaled regional climate model simulations covering the period from 1983 to 2015. The results demonstrated that the annual mean start of growing season (SOS) and length of growing season (LOS) experienced a significant (p < 0.05) decrease and increase with a rate of −2.45 days/decade and 2.98 days/decade, respectively. The significantly advanced SOS and increased LOS were mainly seen in the Western Tianshan Mountains and Ili Valley regions with elevations from 2500 to 3500 m a.s.l and below 3000 m a.s.l, respectively. During the early spring, the significant decline in snow cover fraction (SCF) could advance the SOS. In contrast, snowmelt amount and annual maximum snow water equivalent (SWE) have an almost equally substantial positive correlation with annual maximum vegetation greenness. In particular, the SOS of grassland was the most sensitive to variations of snow cover fraction during early spring than that of other vegetation types, and their strong relationship was mainly located at elevations from 1500 to 2500 m a.s.l. Its greenness was significantly controlled by the annual maximum snow water equivalent in all elevation bands. Both decreased SCF and increased temperature in the early spring caused a significant advance of the SOS, consequently prolonging the LOS. Meanwhile, more SWE and snowmelt amount could significantly promote vegetation greenness by regulating the soil moisture. The results can improve the understanding of the snow ecosystem services in the alpine regions under climate change. [ABSTRACT FROM AUTHOR]

Snowfall is a critical component of the hydrological cycle and water resources supply in mountainous areas. The snowfall regime varies according to time and space, and its uncertainties exist under climate change conditions. It is a necessary process to monitor the moisture characteristics of snowfall so as to investigate the information on snowfall, but a separate study on the snow moisture characteristics did not sufficiently describe over the Tianshan Mountains (TS). This study investigated the spatiotemporal variability of snowfall in the TS during the cold season from 1982 to 2018 based on the Weather Research and Forecasting (WRF) model simulations and analyzed moisture characteristics of snowfall using the regional moisture budget analysis. The results demonstrated that the snowfall amounted to 84.53 mm in the TS during the cold season and experienced a slight increase (P > 0.05). A significant increase in snowfall was noticed in the Eastern TS and the high-altitude regions. Western Eurasia and the Arabian Sea were primary moisture sources of snowfall, and the abundant moisture was transported by the mid-latitude westerly and the southwesterly to the interior. The anomalous cyclone over Europe transported more moisture flux to Central Asia. Meanwhile, the anomalous cyclone of Mongolia and the anticyclone in southwestern Central Asia caused a declining moisture divergence in the TS and an increase of the net moisture budget, which resulted in a snowfall and snow mass augmentation. The obtained study outcomes might improve understanding of snowfall information and provide a scientific reference for water resource management under a warming climate. • Snowfall amounted to 84.53 mm in the Tianshan Mountains during the cold season and experienced a slight increase. • Western Eurasia and the Arabian Sea were primary moisture sources of snowfall, and the abundant moisture was transported by the mid-latitude westerly and the southwesterly to the interior. • A declining moisture divergence in the Tianshan and an increase of the net moisture budget resulted in a snowfall and snow mass augmentation. [ABSTRACT FROM AUTHOR]