24th Pacific Science Congress (PSC-24)

In April 2024, a record-breaking rainfall event occurred in southern China, causing significant socioeconomic impacts. This study investigates the spatiotemporal features of this event and their underlying causes, based on ERA5 reanalysis data and station observations. The results show that this extreme precipitation event exhibited a "strong-weak-strong"  pattern, with heavy rainfall occurring during April 3–7 (P1) and April 16–30 (P3), separated by a dry spell during April 8–15 (P2). Moisture budget diagnostics reveal that anomalous vertical motion and strengthened water vapor convergence predominantly contributed to the increases in rainfall during P1 and P3. Backward trajectory analysis shows that air masses from the northwestern Pacific accounted for 47.2% and 63.7% during P1 and P3, respectively, facilitating the transport of moist air from the ocean to southern China. In contrast, during P2, mid-latitude Rossby waves induced high-pressure anomalies over southern China, with continental air masses from mid-to-high latitudes dominating the trajectories and suppressing precipitation. These results enhance our understanding of the rainfall variability in southern China during early spring, providing important implications for the extended-range forecasts of extreme rainfall events.
In April 2024, a record-breaking rainfall event occurred in southern China, causing significant socioeconomic impacts. This study investigates the spatiotemporal features of this event and their underlying causes, based on ERA5 reanalysis data and station observations. The results show that this extreme precipitation event exhibited a "strong-weak-strong"  pattern, with heavy rainfall occurring during April 3–7 (P1) and April 16–30 (P3), separated by a dry spell during April 8–15 (P2). Moisture budget diagnostics reveal that anomalous vertical motion and strengthened water vapor convergence predominantly contributed to the increases in rainfall during P1 and P3. Backward trajectory analysis shows that air masses from the northwestern Pacific accounted for 47.2% and 63.7% during P1 and P3, respectively, facilitating the transport of moist air from the ocean to southern China. In contrast, during P2, mid-latitude Rossby waves induced high-pressure anomalies over southern China, with continental air masses from mid-to-high latitudes dominating the trajectories and suppressing precipitation. These results enhance our understanding of the rainfall variability in southern China during early spring, providing important implications for the extended-range forecasts of extreme rainfall events.

Extreme rainfall,April 2024,Moisture budget,Backward trajectory,southern China