Abstract: By using the daily air temperature, precipitation, snowfall, and accumulated snow phenomena data from 98 meteorological stations on the Qinghai-Tibetan Plateau (QTP), this paper performs an "at-risk" evaluation on the snow cover formation, including snowfall and accumulated snow on the QTP under the current climatic condition and future climate warming situation. First of all, a critical climate condition is determined based on the daily air temperature and precipitation when there were rainfall, snowfall, or accumulated snow phenomena, that is, taking 0℃ air temperature as the critical condition of temperature between rainfall and snowfall, and 0℃ air temperature and 4.0 mm (autumn) or 3.0 mm (spring) snowfall as the critical conditions between accumulated snow and non-accumulated snow. Analyses based on the above critical conditions disclose that under the current climatic condition, stations with "at-risk" accumulated snow account for 33% and 36% of all stations and the proportions for "at-risk" snowfall reach 78% and 81% in autumn and spring, respectively. Spatially, most stations with "at-risk" accumulated snow locate at the edge of southern and eastern QTP, and stations with the "at-risk" snowfall also exist in the northern edge. If the air temperature increases 2.5℃ by 2050, the snowfall only in a few current "at-risk" snowfall stations will transform into rainfall, but most current "at-risk" accumulated snow stations will face the problem that snowfall is difficult to be accumulated and the stations will become "at-risk" accumulated snow stations, this means that both the snow depth and the snow cover duration over most areas of the QTP will decline, including the delay of the beginning date and the advance of the ending date.

Key words: Qinghai-Tibetan Plateau, snow cover, snowfall, vulnerability, climate change