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<p>South China (SC) experienced a record-breaking extreme rainfall event in April 2024, which caused severe disasters and high socioeconomic losses. In this study, the thermodynamic and dynamic processes and underlying causes of this extreme rainfall event were investigated using a recently developed moisture budget equation. The results showed that the contribution of the dynamic terms (87.6%) to the rainfall anomalies was more significant than that of the thermodynamic terms (–17.4%). Additionally, the dynamic term <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\delta MCDD\)</EquationSource> </InlineEquation> driven mainly by the anomalous meridional circulation (MC), contributed most (68.2%) to the anomalous rainfall, suggesting that the MC plays a significant role in the anomalous rainfall. The anomalous MC was characterized primarily by a “negative–positive–negative” tripolar pattern with rising motion over SC. Further analysis revealed that the anomalous MC was closely related to the sea surface temperature anomaly (SSTA) over the three oceans. The Indian Ocean basin-wide warming (IOBW) during the El Niño decay phase enhanced the western North Pacific anomalous anticyclone (WNPAC), favoring the rising motion of the MC. The significant warming over the tropical North Atlantic led to two anomalous Rossby wave trains, which further resulted in rising motion over SC.</p>

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Impact of meridional circulation on the record-breaking rainfall over South China in April 2024

  • 期刊论文

  • 发表日期：

    2026年4月10日

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  • Chen Cang,
  • Juneng Liew,
  • Jianbo Cheng,
  • Dongdong Zuo,
  • Yuheng Zhao,
  • Guolin Feng

摘要

South China (SC) experienced a record-breaking extreme rainfall event in April 2024, which caused severe disasters and high socioeconomic losses. In this study, the thermodynamic and dynamic processes and underlying causes of this extreme rainfall event were investigated using a recently developed moisture budget equation. The results showed that the contribution of the dynamic terms (87.6%) to the rainfall anomalies was more significant than that of the thermodynamic terms (–17.4%). Additionally, the dynamic term \(\delta MCDD\) driven mainly by the anomalous meridional circulation (MC), contributed most (68.2%) to the anomalous rainfall, suggesting that the MC plays a significant role in the anomalous rainfall. The anomalous MC was characterized primarily by a “negative–positive–negative” tripolar pattern with rising motion over SC. Further analysis revealed that the anomalous MC was closely related to the sea surface temperature anomaly (SSTA) over the three oceans. The Indian Ocean basin-wide warming (IOBW) during the El Niño decay phase enhanced the western North Pacific anomalous anticyclone (WNPAC), favoring the rising motion of the MC. The significant warming over the tropical North Atlantic led to two anomalous Rossby wave trains, which further resulted in rising motion over SC.