夏季青藏高原西北侧水汽绕流对东亚旱涝格局的综合影响研究

Obstructed by the Tibetan Plateau, summer low-level westerly is split into two branches, which causes northern and western moisture flows around the plateau respectively, thus exerts a significant influence on East Asian climate. By Utilizing different reanalysis data and performing various statistical methods, this project firstly analyze spatial-temporal variabilities (including interannual and decadal scales) of two branches of moisture flow (hereafter, NBMF for northern branch of moisture flow and WBMF for western branch of moisture flow), so as to recognize their multi-scale characteristics fully; secondly investigate combined downstream effects of NBMF and WBMF multi-scale variabilities on anomalous summer rainfall patterns in East Asia; finally stress time-lagged evolution of land-atmosphere coupled system associated with NBMF and WBMF, such as thermal and snow cover condition of Tibetan Plateau. The successful development of this project will disclose some key physical processes about impact of Tibetan Plateau on regional climate, and build the conceptual model about the downstream effect linked with mid-latitude westerly, Tibetan Plateau and East Asian rainfall anomaly，which give a great push for a reliable prediction of East Asian summer climate.

夏季青藏高原对中纬西风带有明显的分支作用，形成西侧和北侧两支水汽绕流的通道，势必对东亚旱涝气候产生重要影响。鉴于相关研究的缺乏，本项目拟采用多套再分析资料并综合多种现代统计方法，剖析夏季青藏高原西北侧水汽绕流分支的空间结构及其近50年的演变规律，全面认识青藏高原西北侧水汽绕流变异的多尺度时空特征；重点探讨青藏高原西北侧水汽绕流多尺度变动的下游效应，即对东亚夏季旱涝格局的协同影响；考察高原西北侧水汽绕流变动与地气系统因子（如欧亚积雪和高原热力状况等）变化的时滞关联，从陆气耦合和波列传播的角度凝练青藏高原影响东亚夏季旱涝的某些关键物理过程。此项目的实施，不仅有助于认清青藏高原的区域气候效应，而且有望建立“西风带-青藏高原-东亚旱涝”下游效应的概念模型，为检验和改善东亚夏季气候的模拟与预报能力提供理论依据。

本项目旨在揭示夏季青藏高原西北侧水汽输送变异影响东亚旱涝的关键环流系统及其物理过程。首先，收集和整编多种再分析资料和常规观测资料，经计算处理与对比评估，形成一套有关青藏高原及其周边水汽输送与收支的数据集；其次，利用上述数据集剖析夏季青藏高原西北侧水汽输送分支的空间结构及其年际变化和年代际演变特征，指出青藏高原西侧水汽输送分支影响的局地性，关注大气水分收支和波列传播特征，重点探讨青藏高原北侧水汽输送的变动对东亚夏季旱涝的影响；最后，考察夏季青藏高原北侧水汽输送变异与地气系统因子（如高原热力状况等）的时滞关联，进而辨识青藏高原北侧水汽输送影响东亚夏季旱涝的某些关键物理过程。此外，本项目还超额探讨了以下内容：中国汛期暴雨的年代际跃变及其大尺度环流背景；西北干旱区夏季感热通量的热力参数化比较等。总体而言，本项目基本完成计划所规定的2014-2016年研究任务。相关研究成果已完成学术论文4篇：发表CSCD论文2篇，在审SCI论文2篇。