环境场季节内振荡对中国东南部热带气旋降水的调制作用

利用1985—2015年6—8月登陆中国东南部(福建和浙江)的35个西北行热带气旋(TC)和站点观测的日降水量，根据区域TC过程降水量，分为强降水、适量降水和弱降水TC，分析影响各级TC降水的环境场异常特征及其季节内振荡(ISO)的调制作用。(1)对流层低层850 hPa表现为中心位于福建东部强的气旋异常，来自孟加拉湾和南海强水汽输送在中国东南部产生强的水汽辐合促使TC强降水的发生，其中10~20天和30~60天ISO的环流和水汽输送都有贡献，但东南部的水汽辐合主要受10~20天ISO的影响；与TC强降水相比，TC弱降水对应的异常气旋和水汽辐合明显减弱。(2)影响TC强降水的10~20天ISO环流异常在TC登陆过程，自菲律宾群岛附近向西北方向传播至中国东南部，30~60天ISO环流异常自南海向东北偏北方向传播至台湾西南部，且环流异常强度不断加强。(3)影响TC弱降水的10~20天ISO环流异常自菲律宾西部向北传播，30~60天ISO环流异常自南海南部向东北方向传播。 

MODULATION OF INTRASEASONAL OSCILLATIONS ON RAINFALL INDUCED BY TROPICAL CYCLONES OVER SOUTHEAST CHINA

Using 35 tropical cyclones (TCs) which moved northwestward and made landfall at the southeast of China and observational daily rainfall data at stations during June-August in 1985—2015, this study analyzes the rainfall induced by the 35 TCs, focusing on the modulation processes of intraseasonal oscillation (ISO) in environmental anomalies. The 35 TCs are separated into three types of strong, moderate, and weak rainfall. The results show that for the strong rainfall type, a cyclonic anomaly center appeared in eastern Fujian and strong moisture was supplied from the Bay of Bengal and the South China Sea (SCS), and strong moisture convergence resulted in heavy rainfall in the southeast coast of China. Both the 30~60 day and 10~20 day ISOs of the circulation and water vapor transport contributed to it, but moisture convergence in the southeast coast of China was mainly influenced by 10~20 day ISO. Compared to strong rainfall, cyclonic anomaly and moisture convergence for weak rainfall weakened significantly. For strong rainfall, both the 10~20 day and 30~60 day ISOs persistently enhanced cyclonic anomaly propagating northwestward from the Philippines to the southeast coast of China and northeastward /northward from the SCS to the southwest of Taiwan in the process of TC landfall. For weak rainfall, both 10~20 day and 30~60 day ISOs of cyclonic anomaly propagated northward from the western Philippines and northeastward from the SCS.