华南前/后汛期降水异常与印度洋海温异常的联系与机理

The anomalous precipitation in the first and second rainy season in Southern China has an important impact on the local people's living and the social and economic development. The previous studies mainly focus on the temporal and spatial variation of precipitation anomalies during the first rainy season and the causes of anomalous linkage with the sea surface temperature anomalies (SSTA) in the waters near Southern China. However, the relationship and mechanism between the anomalous first and second rainy season precipitation in Southern China and the SSTA over the Indian Ocean especially the South Indian Ocean is less. Additionally, comparing their similarities and differences is also rare. The project will study the relationship between the anomalous precipitation in first and second rainy season and the different SSTA patterns in the Indian Ocean especially the South Indian Ocean. We will reveal the relationship and causes of precipitation anomalies in first rainy season with the SSTA in the different region of Indian Ocean month by month. The relationship and physical mechanism between the Southern Indian Ocean dipole with the rainfall of Southern China during second rainy season will also research. The similarities and differences in the physical mechanism of the anomalous precipitation in Southern China in first/second rainy season related with the different SSTA patterns over Indian Ocean will be compared. The results will not only contribute to comprehend deeply essential of anomalous precipitation in the first/second rainy season in southern China, but provide useful information to the seasonal rainfall forecast in this region.

华南前/后汛期降水异常对当地人民生活及社会经济的发展有着重要影响。已有研究主要分析华南前汛期降水异常的时空变化规律及和华南临近海域海表温度异常联系的成因，对华南前/后汛期降水异常和印度洋尤其是南印度洋海温异常的联系和成因的研究工作较少，比较它们联系异同的工作亦不多见。本项目将针对华南前/后汛期降水异常和印度洋尤其是南印度洋海温异常的关系进行研究，揭示华南前汛期逐月降水异常和印度洋不同区域海温异常的关系及机理；弄清华南后汛期降水异常和南印度洋偶极子的联系及成因；比较印度洋异常海温不同分布型对华南前/后汛期降水异常影响途径的异同及海温异常型变化机理。研究结果有助于深刻理解华南前/后汛期降水异常的成因，并为华南前/后汛期降水预测提供线索。

华南地区濒临中国南海，处于东亚季风区的南部，是我国经济最为发达的地区之一，人口密集，农林牧副渔业发达。华南降水主要受4-6月的华南前汛期和7-9月的华南后汛期影响，华南前汛期和后汛期降水约占全年降水比重的80%。同时，华南地区亦是中国降水最多的地区。. 项目利用华南地区的站点观测资料、多源大气再分析资料、海表温度资料等数据，并结合大气环流模式，研究了华南地区汛期降水异常的成因。研究成果揭示了华南地区降水异常和印度洋及太平洋海温异常的关系及物理机制。两广地区存在前汛期降水正（负）异常、后汛期降水负（正）异常的反位相现象，这种反位相现象与热带西太平洋海温异常存在密切联系。前汛期期间，热带西太平洋海温时，可引起有利于华南降水异常偏多的大气环流条件。热带西太平洋海温异常可持续至后汛期，而大气异常的响应则不利于两广地区降水的产生。. 华南后汛期降水异常与热带印度洋中部（东和西部）呈显著正（负）相关关系，即华南后汛期降水异常和IOD Modoki事件存在联系。IOD Modoki正异常可通过影响低纬及中高纬途径调节华南地区水汽异常及大气环流异常等条件引起降水异常。. 华南前汛期降水异常还和热带北太平洋（tropical northern Pacific，TNP）海温呈负相关关系。热带北太平洋海温正异常，通过Mastuno-Gill响应引起西北太平洋气旋式环流异常，中国南海东风异常，减弱了南海夏季风，华南至中国南海地区对流层低层存在异常反气旋环流。水汽及环流条件也不利于华南地区降水的产生。项目研究成果可为华南地区的防灾减灾工作提供科学依据和线索。.