北极涛动对印度洋气候的影响及其机理研究

This proposal aims to study the interannual relationship between the Arctic Oscillation (AO) and the tropical Indian Ocean (TIO) precipitation in boreal winter, by employing observation and numerical simulation data. First, to examine their statistical relationship and the associated changes of the relevant variables, including the spatial features of the atmospheric circulation,three-dimensional structures of the circulation, activity of the quasi-steady Rossby waves,and the surface oceanic thermal anomalies of SST and thermocline. Particularly, to explore the physical consistency among these variables and the relevance to the Indian Ocean precipitation. Second, based on the observational analysis to present a physical explanation for the mechanism(s) connecting the Arctic Oscillation and Indian Ocean precipitation. Third, using climate model to simulate the Arctic Oscillation-Indian Ocean precipitation connections, and to test the robustness of their teleconection with considering the key variables and the involved physical processes.

结合观测和模拟，分析年际尺度北半球冬季北极涛动与热带印度洋降水、ITCZ的可能联系。诊断其联系过程中相关物理环节的特征和细节，包括大气环流变化的空间特征，三维环流的异常，定常Rossby波的活动，海洋表层热量状况(SST和温跃层)的异常，检查这些要素相关变化的物理一致性及其与降水的关联。根据观测诊断结果，明确北极涛动影响印度洋气候的可能机理及影响过程。在此基础上，利用气候模式对涉及北极涛动和印度洋气候联系的过程进行数值模拟，检验其联系机理的真实性。

印度洋海气系统是亚洲季风气候的重要部分，以往研究表明热带因子和过程是印度洋气候变率的重要来源。相对而言，热带外的因子研究较少。本研究结合观测和模拟，分析年际尺度北半球冬季北极涛动对热带印度洋降水、ITCZ、海温等的可能影响及其机理。发现冬季北极涛动强的正位相时，通过大气波列影响印度洋对流层低层风场异常，导致同季节南印度洋中部ITCZ降水增强。另一方面冬季风应力旋度异常激发的下沉海洋Rossby波，可导致北半球夏季西印度洋海表温度的显著异常偏高。同时，伴随Rossby波西传，次表层温度及上层海洋热含量的持续性异常，可进一步导致相邻的东非大陆短雨季降水增加以及阿拉伯海经向季风环流的异常。冬季北极涛动指数对夏季西印度洋海温异常的预测具有指示意义。

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