Research progress on moisture source change of precipitation over the Tibetan Plateau and its surrounding areas
This paper provides a comprehensive review of recent studies on the moisture sources of precipitation over the Tibetan Plateau and its surrounding areas, focusing on the characteristics of moisture sources (regions of evaporation) for precipitation, the spatiotemporal changes in contribution of moisture sources to precipitation, and the causes of changes in moisture source associated with wetting trend over the Tibetan Plateau and drying trend in Southwest China (located in the southeastern margin of the Tibetan Plateau). The existing studies show that the moisture transports from the west of the Tibetan Plateau by mid-latitude westerlies in the Northern Hemispheric and from the southwest by the Indian summer monsoon contribute the most to precipitation over the Tibetan Plateau. The moisture transports from the west show an overall decreasing trend while those from the south and the east show an overall increasing trend in the past three decades.The enhanced water vapor transport from the monsoon regions and the intensified local hydrological recycling are the primary reasons behind the recent wetting trend over the Tibetan Plateau, while the reduced water vapor transport from the regions dominated by the westerlies is the main factor that causes the drying trend in the southeastern margin of the Tibetan Plateau.This paper discusses the challenges and future directions for understanding the variation of moisture source of precipitation over the extended Tibetan Plateau area. Firstly, the observational evidence of moisture source variation is still lacking. There is a need to reduce uncertainty of the moisture source estimates through integration of model and observations.Secondly, the changes in glacier, lake and vegetation over the Tibetan Plateau and the associated changes in evapotranspiration would affect the water vapor transport and recycling.There is a need to quantify the interactions between land surface change and precipitation over the Tibetan Plateau and its surrounding areas from the perspective of water vapor sources. Thirdly, the enhanced moisture supply from the monsoons and reduced moisture supply from the westerlies could be linked to climate change as the projection of future precipitation changes under a warming world shows the same pattern as the past three decades, i.e.a wetting trend over the Tibetan Plateau and a drying trend in the southeastern margin.However, further researches are needed to understand the linkages between global change and moisture source variation over the Tibetan Plateau and its surrounding areas.
