Snow cover expansion with contrasting depth thinning in the recent 40 years: Evidence from the Yalong River Basin, South-eastern Tibetan Plateau

Yalong River Basin, Southeastern Tibetan Plateau, China. The spatio-temporal variability of snow characteristics are important indicators of climate change. Based on statistical analyses of remote sensing data from 1979 to 2018, this study explored changes of snow characteristics and climate parameters in the basin. This region has, despite rapidly changing ambient conditions, not previously been investigated at the current level of detail, including multiple snow-related variables. We show that the average snow depth (SD) decreased over the considered 40-year period, while the snow covered days showed an opposite, increasing trend. This pattern was attributed to a combined effect of a gradually earlier arrival of the first snow and a gradually later arrival of the last snow, with overall more frequent occurrence of instantaneous snow cover. Such short-duration snow events are likely linked to regionally increasing precipitation amounts and intensities that on an event basis can outweigh melting effects of increased temperatures. The results furthermore underscored a high degree of spatio-temporal heterogeneity within the basin, not least in SD, which decreases in 27 % and increases in 73 % of the basin. These findings have crucial implications for energy budgets and frozen season length of the basin, raising questions about the prevalence of similar dynamics across the Tibetan plateau.