Remote Precipitation Events Over South China Related to the Bay of Bengal Tropical Cyclones During the Pre-Summer Rainy Season

Tropical cyclones (TCs) originating in the Bay of Bengal (BOB) can induce heavy rainfall in remote South China, primarily due to the abundant tropical moisture transporting from the vicinity of BOB TCs. This study analyzes 28 TC remote precipitation (TRP) events occurring over South China during the pre-summer rainy season (April to June) from 1979 to 2021, from a synoptic climatology perspective. On average, TRP events persisted for about 3 days, with primary precipitation centers identified in northeastern Guangxi Province, central and coastal areas of Guangdong Province, and the region from western Fujian to central Jiangxi, resulting in above-normal rainfall intensity in northern South China. Employing the objective classification method of the self-organizing map, we identified three key configurations conducive to TRP occurrence, including synoptic patterns dominated by BOB TCs in conjunction with the southern branch trough (P1), the western Pacific subtropical high (WPSH, P2), or the prevailing southwest monsoon (P3). P1 and P2 exhibited three precipitation centers similar to those in the overall TRP events, while P3 corresponded to weaker precipitation due to less pronounced frontogenesis, with its center located in the southern warm-sector region of South China. Additionally, the stronger and more northerly WPSH in P2 caused a northward shift in the water vapor flux reaching South China compared to P1, enhancing the precipitation in northern South China. This study extends the perspective of TRP events in subtropical regions, holding significant implications for weather forecasts in downstream regions affected by BOB TCs.