Different maximum precipitation altitudes and precipitation gradient characteristics of different basins in the Third Pole region

Abstract

Investigation of maximum precipitation altitude (MPA) and precipitation gradients supports the understanding of vertical precipitation distribution in the mountains and obtaining accurate areal precipitation datasets. This study provided the MPAs and precipitation gradients of 524 subbasins based on Integrated Multi-satellite Retrievals for Global Precipitation Measurement (IMERG) and discussed the dominant factors for the spatial pattern of MPAs and precipitation gradients. The results show that the MPAs across all subbasins in the Third Pole (TP) have noticeable seasonal variation, with the highest mean MPAs in winter (3803.2 m) and lowest mean MPAs in summer (3646.8 m). At the spatial scale, the MPAs are located at lower altitudes in the Himalayas, western Kunlun and Hengduan Mountains (<1500 m); in the Tienshan Mountains and Pamir, the MPAs mainly lie at middle altitudes (2000–3500 m); and in the interior of the TP, Tanggula Mountains and Karakoram Mountains, the MPAs exist at higher altitudes (>4500 m). Additionally, the precipitation gradients had different characteristics above and below the MPAs. Below the MPAs, there is a positive annual mean precipitation gradient of 11.35 mm/100 m, and the larger positive precipitation gradients are mainly located in the Himalayas, Hengduan Mountains, and western Kunlun. Above the MPAs, there is a negative annual mean precipitation gradient of − 8.61 mm/100 m, and smaller negative precipitation gradients are mainly located in the Himalayas and western Tienshan Mountains. Further discussions indicated that MPAs and precipitation gradients have a positive correlation with wind speed but a negative correlation with water vapor flux, the angle between wind direction and the aspect of mountains (AWA). The maximum effect of wind and topography on precipitation occurs when the AWA is close to 0, and the precipitation gradients are the largest.