Suppressive effect of tropical cyclones over the South China sea on extreme rainfall in southern China

This study reveals that tropical cyclones (TCs) over the South China Sea (SCS) significantly suppress the occurrence frequency of extreme rainfall over Southern China (SC). While TCs, when they traverse the SCS, reduce rainfall across all intensities, the most pronounced suppression is observed in extreme rainfall, with reductions exceeding 40%. It is found that the unique thermal background plays an important role in favoring the rainfall suppression effect of TCs. Climatologically, SC serves as a warm and moist center in summer, characterized by high equivalent potential temperature values that stretch eastward and northward and exhibit pronounced zonal and meridional gradients. When TCs enter the SCS, SC is dominated by strong easterly anomalies on the northern flank of TCs. These anomalies induce the advection of cold, dry air over SC and lead to significant subsidence. Consequently, the occurrence frequency of extreme rainfall is substantially diminished. Further analysis of rainfall and circulation evolutions confirms the crucial role of the unique thermal background in anchoring the suppressed rainfall to the northern flank of TCs. As TCs move into the SCS and make landfall, suppressed rainfall over inland areas can persist for approximately one week, while in coastal areas, rainfall initially decreases and then transitions to extreme rainfall. This study provides a new insight into the impact of TCs on extreme rainfall over SC. • TCs suppress extreme rainfall over SC by over 40% when traversing the SCS; • The unique thermal background anchors suppressed rainfall to TCs’ northern flank; • TC-induced suppressed rainfall over inland SC can last for approximately one week; • Coastal areas experience a transition from reduced to extreme rainfall.