Characterizing precipitation in high altitudes of the western Tibetan plateau with a focus on major glacier areas

Abstract

AbstractSolid water resources such as glaciers and snow cover are widely distributed in the western Tibetan plateau (WTP), and precipitation is the key supply of them. However, the characteristics of precipitation over the WTP remain unclear due to sparse observations. Using observation‐based gridded data (APHRODITE, GPCC), satellite products (TRMM, GPM), reanalysis data (ERA5, ERA‐Interim, JRA‐55) and weather research and forecasting model (WRF)‐simulation data (HAR10, HAR30), this study investigated the precipitation characteristics in high mountain areas (altitude >2,500 m a.s.l.) of the WTP (26–44°N, 70–85°E) from 2001 to 2013. Results show that annual GPM precipitation (336 mm) is much lower than that of other data sets (570–800 mm) for the WTP and appears to be an outlier; meanwhile, the other data sets show increasing precipitation as grid resolution decreases (becomes coarser). In contrast, high spatial resolution WRF simulations (HAR10, HAR30) yielded considerably higher precipitation in four strongly glacierized alpine areas (Western Himalaya, Karakorum, Tajikistan, and west Kunlun) than the other data sets. When compared to precipitation estimated using the water balance in nine glacierized catchments of the Upper Indus River Basin, the HAR data sets more reasonably represent the amount of precipitation in high mountain areas than the other data sets. The surface albedo, snow cover extent, and snow cover duration observed by satellites further indicate that the HAR data sets yield reasonable spatial variability of precipitation. This implies that the commonly used data sets (such as observation data and satellite products) underestimate the precipitation in high mountain areas. According to the HAR10 data, the four major glacierized areas on the WTP have similar precipitation amounts in summer and autumn, and the winter–spring contribution to annual precipitation is at least 70% in three of these areas (Western Himalaya, Karakorum, and Tajikistan). This pattern indicates that precipitation over the high‐altitude areas in WTP is mainly controlled by the mid‐latitude westerlies. The annual precipitation in these areas is over 1,000 mm, which is comparable to that of the southeast TP but much larger than that on the central plateau. Therefore, the spatial precipitation pattern across the TP is ‘wet east and west, dry middle’.