青藏高原及其周边地区降水的水汽来源变化研究进展

Research progress on moisture source change of precipitation over the Tibetan Plateau and its surrounding areas

近几十年来,随着全球气候变暖,青藏高原降水整体呈现增加趋势,气候暖湿化趋势明显;与此同时,位于青藏高原东南缘的中国西南地区整体上呈现暖干化趋势,干旱事件频发。探讨青藏高原及其周边地区降水的水汽来源变化、揭示降水趋势性变化的原因已经成为当前研究热点。本文评述了近年来青藏高原降水的水汽来源研究,重点关注青藏高原变湿、西南地区变干的水汽来源变化原因以及青藏高原南北水汽来源差异,讨论了尚未解决的科学问题,展望了未来研究方向。现有研究表明,青藏高原以西的西风带控制区蒸散发贡献的水汽整体呈现减少趋势,青藏高原以南和以东的季风控制区蒸散发贡献的水汽整体呈现增加趋势,上述水汽源区贡献变化导致了青藏高原及其周边不同区域降水趋势性变化的差异。展望未来,水汽来源分析的模型和数据需要进一步验证及减少不确定性,青藏高原下垫面和蒸散发变化对周边地区降水的影响机制研究有待加强,全球变化与青藏高原降水水汽来源变化的关系尚需深入分析。

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.