Tropical Cyclone Rainfall Structure and Its Long-term Trend over the Western North Pacific

Abstract

Abstract The tropical cyclone (TC) rainfall structure over the western North Pacific is categorized into four typical types. Clusters I and IV are featured by the southward-shifted and northward-shifted rainfall centers, respectively. Meanwhile, Clusters II and III are characterized by the weak and strong maximum rainfall rates near the TC center, respectively. Apart from rainfall, Clusters I–IV show diverse features in locations, intensities, and lifetime stages. Both Clusters I and III appear over the low-latitude regions. However, TCs in Cluster III have the strongest intensity and are in the mature stage of their lifetime, while TCs in Cluster I are relatively weaker and in earlier stages. On the contrary, Cluster IV has the highest mean latitude positions and strong intensity, mainly in their later lifetime period. Cluster II shows the weakest TC intensity and mainly locates in the subtropics. Diverse TC locations lead to different effects of large-scale circulation on TC rainfall patterns in Clusters I–IV. For Clusters I and III, abundant moisture provided by the southwest monsoon causes heavy rainfall. In contrast, Cluster IV is mainly affected by mid-latitude westerly troughs, which is responsible for the northward-shifted rainfall center. Cluster II shows the weakest TC intensity, resulting in a small rainfall rate. Further analysis shows that the changes in the relative frequency contributed 36% of the decreasing trend of basin-mean inner-core rainfall during 1998–2019, where the shift of rainfall pattern from Cluster III to Cluster I due to the enhanced monsoon plays a central role.