Analysis of Precipitation Phase Transition Characteristics and Prediction Indices in Qinghai Plateau

Using the observation data from 50 ground-based meteorological stations in Qinghai Plateau during 2006-2020 and ERA-Interim reanalysis data, the linear tendency estimation and probability density analysis are used to reveal the spatial-temporal distribution characteristics of precipitation phase transition and prediction indices in Qinghai Plateau. Meanwhile, the observation data in 2021 are also verified. The results show that: (1) The spatial-temporal distribution of precipitation phase transition is closely related to altitude. It mainly occurs in late spring, early summer and autumn, concentrated in the Qilian Mountains and Southern Qinghai; (2) Precipitation phase is closely related to the low-level temperature. The height of the characteristic temperature layer (0 ℃ layer, -5 ℃ layer, etc.), which is relative to the ground, T_2m and the temperature of the characteristic pressure layer (500 hPa, 600 hPa, 700 hPa) can be used as the phase prediction indices; (3) The prediction indices of rain-to-snow and snow-to-rain are significantly different, and the temperature lapse rate from ground to 0 ℃ layer of snow-to-rain process is greater than that of rain-to-snow process; (4) The verification results show that the temperature indicators at the lower level and T2m exhibit satisfactory applicability, while there is a certain deviation at the middle and higher levels.