Discriminating types of precipitation in Qilian Mountains, Tibetan Plateau

Study regionHulugou River Basin (HRB) of Qilian Mountains, eastern edge of Tibetan Plateau.Study focusTraditional manual observations only record point-scale precipitation rather than regional-scale precipitation. Automatic weather stations just record precipitation amount without discriminating by type of precipitation. This study observed precipitation types all over the HRB and analyzed air temperature and humidity conditions at daily and half-hour resolution.New hydrological insights for the regionCombined observations of air temperature and precipitation type indicate that, at daily resolution the threshold air temperature between rain and snow is 0 °C and the air temperature at rain/snow boundary is from 0 °C to 7.6 °C, which means the rain and mixed precipitation threshold air temperature can shift more than 7.0 °C in the HRB. At half-hour resolution, air temperature is above 0 °C during rainfall, under 0 °C for snowfall, and above 0 °C at the rain/snow precipitation boundary, and could either be above 0 °C or fluctuate around 0 °C for mixed precipitation. Corresponding relative humidity observations indicate that rainfall and mixed precipitation events correspond with high humidity conditions in warm season of the HRB. Snowfall events correspond with low humidity conditions in the HRB.