Partitioning Solid and Liquid Precipitation over the Tibetan Plateau Based on Satellite Radar Observations

Abstract

Whether precipitation falls in the form of rain or snow is of great importance to glacier accumulation and ablation. Assessments of phase-aware precipitation have been lacking over the vast area of the Tibetan Plateau (TP) due to the scarcity of surface measurements and the low quality of satellite estimates in this region. In this study, we attempt a satellite radar-based method for this precipitation partition, in which the CloudSat radar is used for snowfall while the Global Precipitation Measurement Mission radar is used for rainfall estimation. Assuming that 11-yr snowfall and 5-yr rainfall estimates represent the mean states of precipitation at each phase, the phase partition characteristics, including its annual mean, spatial pattern, seasonal dependence, and variation with elevations, are then discussed. Averaged over the highland area (over 1 km above mean sea level) in TP, the annual total precipitation is estimated to be around 400 mm, of which about 40% falls as snow. The snowfall mass fraction is about 45% in the northern and 30% in the southern part of TP, and about 80% in the cold and 30% in the warm half of the year. Surface elevation is found to be a high-impact factor on total precipitation and its phase partition, generally with total precipitation decreasing but snowfall fraction increasing with the increase of elevation. While there are some shortcomings, the current approach in combining snowfall and rainfall estimates from two satellite radars presents a useful pathway to assessing phase-aware precipitation over the TP region.