资源环境科技发展态势分析平台

Orographic clouds and precipitation are critical to the water cycle and ecology of arid and semiarid mountainous regions. This study intended to investigate the spatial and seasonal distribution of the cloud water path (CWP), precipitation amount, and precipitation efficiency (PE) on the Qilian Mountains (QM) of the northeastern Tibetan Plateau, as well as the related mechanisms linked with topographic distribution and water vapor transport. To solve the limitations of rain gauges and radar observations at high elevations of the QM, we used the latest multiple datasets, including the Global Precipitation Measurement (GPM), Advanced Very High Resolution Radiometer, and ECMWF Reanalysis v5 data from 2016 to 2019. The amount of precipitation retrieved from the two GPM products was evaluated using rain gauge data. The results show that the GPM data generally overestimate the precipitation amount on the QM and have a high correlation with rain gauge data in warm seasons and a low correlation in winter seasons, primarily due to the significant influences of snow and ice coverage. The terrain height and water vapor supply below 600 hPa are two critical factors that determine the spatial and seasonal distributions of clouds and precipitation in the QM. The precipitation generally increased with an increase in terrain elevation below 3000 m and decreased above 3000 m on the QM. CWP, precipitation amount, and PE in the mountainous areas are much higher than those in the surroundings and decrease from the southeast to the northwest because of the decrease in low-level water vapor supply. CWP, precipitation amount, and PE were the highest in summer because of the strong moisture transport from the southeast and the lowest in winter because of the weakest water vapor transport. Water vapor fluxes from the eastern, southern, and northern boundaries contributed to the wetness of the eastern and northeastern slopes of the QM. The lack of low-level water vapor in the westerly winds was the main reason for drought in the western QM.