东亚季风区季节内振荡的年际变化及其对中国东部夏季降水异常的影响

The frequently anomalous summer monsoon rainfall, which occurred over subtropical East Asian Summer Monsoon (EASM) region, may bring about severe drought/flood for the eastern area of China. However the interannual variations of the summer rainfall in eastern China are often associated with the activities of intraseasonal oscillation (ISO).This proposal aims to study the interannual variations of ISO and its impact on the rainfall over eastern China in the summer time. The interannual variations of ISO, such as the spatial-temporal and vertical structures and evolution characteristics will be investigated in the EASM region. The causes of the interannual variations of ISO are going to be discussed. The large scale circulation factors, which affecting the interannual variations of ISO from the tropics and middle-high latitude, respectively, will be analyzed. Besides, the effect of ISO perturbation on summer mean precipitation over the eastern China will be further studied. The moisture budget and momentum equations are applied to compute and diagnose the contributions of ISO perturbation to the variations of summer rainfall in EASM region. The results are expected to make clear the structures and propagation features of ISO in EASM region; to enhance the understanding of physical relationship between the ISO activities in EASM and intraseasonal variability of large-scale circulations from tropics and middle-high latitude, the relationship between the ISO and tropical oceans; and also to help us to understand the possible physical process and mechanism of ISO perturbation on summer rainfall over eastern China.

东亚副热带季风区夏季降水的异常变化是导致我国东部地区夏季旱涝等灾害气候事件的直接原因，而我国东部地区的夏季降水常常受到大气季节内振荡（ISO）活动的影响。本项目拟围绕东亚季风区夏季ISO的年际变化及其成因，以及ISO扰动对我国东部夏季降水异常的影响展开研究。首先分析对我国东部地区夏季降水有重要影响的ISO三维时-空结构演变及其年际变化特征，讨论制约东亚季风区夏季ISO年际变化的影响因子，揭示热带和中高纬的大气环流对ISO的振荡强弱及其结构演变的调制作用，以及热带海洋海温的变化对东亚季风区ISO活动的影响；从动力学角度诊断东亚季风区ISO扰动影响我国东部地区夏季降水的物理过程和可能机制。研究结果将有助于提高对东亚季风区夏季ISO活动规律及其三维结构发展演变的认识，增强对ISO 的年际变化与热带和中高纬大气环流及与热带海洋的物理联系的理解。

我国东部地区夏季洪涝灾害事件的发生通常是由该地区的夏季降水异常偏多造成的，而夏季降水异常与东亚夏季风和大气季节内振荡活动有着直接密切的联系。本项目围绕东亚季风区夏季大气季节内振荡的年际变化及其成因，以及大气季节内振荡扰动对我国东部夏季降水异常的影响开展了研究。（1）诊断分析了影响我国东部地区夏季降水的大气季节内振荡的三维时-空结构演变特征；（2）揭示了来自中高纬的大尺度环流季节内变率以及来自热带环流共同制约东部夏季降水的季节内振荡特征；（3）深入探讨了大气季节内振荡扰动通过水汽平流和水汽辐合等物理过程的尺度相互作用对夏季风降水的反馈机制；（4）利用气候系统数值模式对大气季节内振荡进行了结构演变及其年际变化的模拟和分析，同时检验了该模式对热带大气季节内振荡的模拟能力。本项目取得的主要研究成果，可为次季节降水预测提供理论依据和有价值的参考，为相关业务预测提供诊断技术支撑，目前已被应用于国家气候中心梅雨监测与诊断业务中，并获得国家气候中心科技成果认定和中国气象局科技成果登记；基于数值模式模拟的大气季节内振荡时空频谱和传播特征，完成一项针对热带大气季节内振荡的波数、周期/频率、振幅及其传播方向和速度等信号的集成分析与识别技术，获得1项软件著作权。此项目资助下正式发表学术论文共7篇（其中SCI论文5篇），完成1项软件著作权，获得1项部级科技成果认定登记。