Activities of tropical cyclones (TCs) over the Bay of Bengal (BoB) often exert appreciable influences on precipitation in China, but how and to what extent these influences operate remain unclear. This study utilizes the International Best Track Archive for Climate Stewardship (IBTrACS) dataset and infrared satellite images from Japan during 1996–2021 to analyze the cloud system structure patterns associated with BoB TCs (excluding tropical depressions) and their impact on China rainfall. A fuzzy c–means clustering method was employed to classify TC cloud clusters into three morphological types: Type “6” (T6) and Type “9” (T9), with cloud distributions predominantly located north (south) of the TC center; and type “symmetry” (TSM), with relatively balanced cloud distributions on both sides. The results indicate that T6 (41.3%) occurs most frequently in autumn, T9 (31.2%) peaks in early summer, and TSM (27.5%) also shows a slight preference for autumn. Distinct circulation features are associated with each type. At 500 hPa over the Qinghai–Xizang Plateau (QXP), T6 is associated with the southern branch trough, T9 with straight westerlies, and TSM with a ridge. At 200 hPa, both centers of T6 and TSM are located at the periphery of the South Asian high (SAH), with enhanced upper-level divergence outflows, resulting in northward extension of cloud clusters under the influence of the westerly jet. In contrast, T9 TCs are embedded within the SAH, where weaker divergence outflows restrict northward cloud development. All three types are characterized by a column-integrated water vapor channel extending from the BoB to southern China, with T9 exhibiting the strongest moisture transport to China. Precipitation analyses reveal that all three types contribute to rainfall in Yunnan Province and the Guangxi Zhuangzu Zizhiqu. Moreover, T6 produces heavier rainfall in southern Xizang Zizhiqu (abbreviated as Xizang hereafter), T9 in Yunnan Province, and TSM in Sichuan Province and Xizang. Remote precipitation induced by TC long-distance moisture transport also exhibits distinct patterns: under T6, high-rainfall areas are widely distributed across southwestern China and parts of southern China; under T9, heavy rainfall is concentrated in southern China; and under TSM, heavy rainfall is mainly confined to Guangdong and Jiangxi provinces. These results provide useful insights for precipitation forecasting in China based on the cloud cluster patterns of the BoB TCs.

Tropical cyclones over the Bay of Bengal (BoBTC) affect the precipitation over China, with distinct seasonal and daily variabilities. This study quantitatively examines the daily standardized precipitation anomalies (SPAs) over China on the days with BoBTC activities (storm-days) and related circulations, based on rainfall measurements at surface meteorological stations and ECMWF reanalysis data on a 0.25° × 0.25° resolution during 1979–2019. Significant positive SPA is found over the stations in the two adjacent regions around BoB (Southwest China in May/November and southern Tibetan Plateau in October) and three distant regions (Southeast China and the northeastern boundary of the Qinghai–Tibet Plateau in May, and central North China in October). The SPA distributions are remarkably consistent with the integrated water vapor transport (IVT) anomalies. Enhanced IVT is found associated with the interaction between southwesterly (southerly) of the BoBTC circulation and low-level monsoonal flow in May (midlevel westerly in winter months). The probabilities of extreme precipitation (EP) occurrences over the above regions all increase on storm-days. For adjacent regions, EP is significantly correlated with the northward IVT anomalies to the east of BoBTC circulation, which strengthen the water vapor input through the southern border. Such IVT anomalies are stronger in May, benefited by the deep monsoonal southwesterlies than those in November. For distant regions, EP is more closely related to the IVT anomaly extending back from BoB. Enhanced moisture from BoB concentrates along a local low-level convergence line over Southeast China, being further facilitated by coexistence of the BoBTC depression and midlevel westerly trough in midlatitudes. Our results highlight the interactions between BoBTCs and local weather systems that influence the general precipitation anomalies and occurrence of EP over China, especially over distant regions.