Spatiotemporal variations of snow cover days on the Tibetan Plateau

Snow cover, as the main existing form of cryosphere on the Tibetan Plateau, is the seasonally fastest changing surface feature. The Tibetan Plateau constitutes the largest high mountain snow and ice-covered area in the Northern Hemisphere and the main snow-covered area in High Mountain Asia. Considering that the variation of snow cover in the high mountain regions of the Tibetan Plateau is largely unknown and research on snow cover days (SCDs) on the Tibetan Plateau is inadequate, we analyzed the spatiotemporal variations of the number of SCDs on the Tibetan Plateau from 2004 to 2021 based on the daily NOAA IMS 4 km snow and ice products. The results indicate the following. (1) Over the past 17 years, the number of SCDs on the Tibetan Plateau has increased markedly at the rate of 11.5 d·(10a)-1. Spatially, the number of SCDs in the high-altitude areas mainly increased in the central and eastern parts but decreased in the south and northwest. (2) The number of SCDs on the Tibetan Plateau exhibits a considerable dependence on elevation; the higher the elevation, the longer the snow cover duration and the greater the number of SCDs. The mean number of SCDs is less than 5 days below 2000 m a.s.l., whereas it exceeds 157 d at 6000 m a.s.l. (3) The annual mean number of SCDs is 71.1 d, with the highest in winter (27.2 d), followed by spring (22.1 d), autumn (14.5 d), and summer (5.3 d). (4) In a general warming and wetting environment in the Tibetan Plateau, the increase in snow cover over the past decade due to more precipitation in high-altitude and high-latitude areas has effectively compensated for the decrease in snow cover due to temperature increase.