青藏高原和热带印度洋加热对新疆夏季降水的协同影响

The thermal forcing over the Tibetan Plateau (TP) and the tropical India Ocean (IO) both have important impacts on climate, not only in the monsoon regions but also in the arid zones, in China. The previous studies, about the concurrent effects of the two abnormal thermal forcing on the regional climate change, which are still not very clear over the arid zones in northwestern China, have been more concentrated on the eastern Asia monsoon regions. Aiming at the concurrent effects of the thermal forcing over the TP and the tropical IO on summer rainfall in Xinjiang arid zone, China, used by the methods of diagnosis and simulation, the spatial differences of summer rainfall in Xinjiang arid zone and corresponding to the characteristics of large-scale atmospheric circulation and water vapor transportation in different thermal forcing pattern over the TP and tropical IO are investigated. From the point of individual effects of thermal forcing over the TP and tropical IO on summer rainfall in Xinjiang arid zone, the contribution differences of the thermal forcing over the TP and tropical IO in the formation of two-centers mode of the South Asia high and the north-to-south oscillation of the Iran high are analyzed, and the relative contribution of the forcing over the TP and tropical IO in transporting two-step process of water vapor is revealed. From the point of concurrent effects of thermal forcing over the TP and tropical IO on summer rainfall in Xinjiang arid zone, the influencing differences of previous sensible heat and latent heat over the TP and SST over the IO on large scale circulation adjustment related to summer rainfall in Xinjiang are distinguished, and the combining mechanisms of the forcing over the TP and tropical IO in transporting two-step process of water vapor are illustrated. From the perspective of different underlying thermal forcing, this project will enhance our understanding in the mechanism of the dry and wet climate change in the arid regions.

青藏高原和热带印度洋热力强迫均对我国天气气候有着重要影响，二者热力强迫对区域气候协同影响的研究更多集中在东亚季风区，如何影响西北干旱区尚不清楚。本项目围绕青藏高原和热带印度样热力强迫对新疆夏季降水的协同影响问题，采用诊断分析和数值模拟的方法，研究前期和同期青藏高原和热带印度洋加热不同空间型，新疆降水的空间差异和对应的大尺度环流和水汽输送特征。从青藏高原和热带印度洋加热单独影响的角度，揭示高原和热带印度洋加热对南亚高压双体型形成和伊朗高压“南北振荡”的贡献差异，弄清二者在不同路径水汽输送两步过程中的具体作用；从高原和热带印度洋加热协同影响的角度，区分高原前期感热和同期潜热与热带印度洋SST异常对大尺度环流调整的影响差异，阐明高原和热带印度洋热力异常在热带印度洋不同路径水汽向北输送过程中的配合机制，加深对干旱区气候干湿变化机理的理解。

青藏高原和热带印度洋热力强迫均对我国天气气候有着重要影响，二者热力强迫对区域气候协同影响的研究更多集中在东亚季风区，如何影响西北干旱区尚不清楚。本文基于诊断和数值模拟的方法，分析了青藏高原和热带印度洋热力强迫对新疆夏季降水的协同影响，揭示了可能的单独和共同影响机制。结果发现5月和夏季青藏高原及热带印度洋热力异常均与新疆夏季降水联系紧密，但是影响区域有所差异，青藏高原和热带印度洋加热均可单独影响新疆夏季降水。热带印度洋海温偏暖时，导致中亚副热带西风急流位置偏南，南亚高压呈双体型分布。同时减弱了南亚夏季风环流，印度半岛上空受异常反气旋控制，将阿拉伯海水汽输送至中纬度地区（30°N），是水汽两步输送的第一步。青藏高原北部夏季潜热加热偏强时，加强了高原夏季风。高原西北侧对流层高层出现异常反气旋环流，有利于高纬冷空气向南输送，导致中亚对流层中高层变冷。由热成风原理，中亚上空受异常气旋环流控制，对应中亚副热带西风急流南移，对流层中层的异常气旋接力将中纬度水汽继续向北输送至新疆上空，这是水汽两步输送的第二步。青藏高原和热带印度洋加热均偏强时，对新疆夏季降水的影响要大于单一加热。二者共同加热导致中亚副热带西风急流位置偏南，南亚高压双体型分布，中亚和印度半岛上空分别受异常气旋和反气旋控制，阿拉伯海水汽通过两步输送进入新疆上空。以上有利的大尺度环流和水汽条件共同贡献了新疆夏季降水的增多。