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<p>The spatiotemporal patterns of moist heat wave days (MHWD) in South China (SC) during boreal summer from 1979 to 2021 were analyzed using multiple observational and reanalysis datasets. The occurrence of MHWD in SC was influenced by the tropical Indian Ocean sea surface temperature anomalies (SSTA). The study indicated significant interannual and interdecadal variability in MHWD, with a notable positive correlation between MHWD and concurrent warming in the tropical Indian Ocean. The Indian Ocean Basin Mode (IOBM) warming, which is associated with the decay phase of El Niño events, plays a crucial role in this relationship. The summer IOBM warming can reinforce and maintain the anomalous anticyclonic circulation in the mid-lower troposphere over the western Pacific through eastward-propagating Kelvin waves, intensifying the western Pacific subtropical high (WPSH) at 500&#xa0;hPa. Thus, this induces anomalous low-level divergence and upper-level convergence, controlled by anomalous descending motion, which extends from the northwestern Pacific to SC. This results in suppressed convection and further increased short wave radiation reaching the surface, thereby promoting high temperatures over SC. Meanwhile, the anomalous southwesterly water vapor and high moist static energy (MSE) related to anticyclonic circulation anomaly may transport from the western Pacific into SC, leading to sufficient moisture over SC. Our results reveal an interannual relationship between tropical Indian Ocean SSTA and MHWD in SC, which could be beneficial to improve predictions of extreme events in relevant regions.</p>

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Interannual relationship between moist heat waves in South China and tropical Indian ocean sea surface temperature anomalies and possible mechanisms during boreal summer

  • 期刊论文

  • 发表日期：

    2025年4月16日

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  • Shaoxu Wu,
  • Dachao Jin,
  • Xudong Wang,
  • Jing-Jia Luo

摘要

The spatiotemporal patterns of moist heat wave days (MHWD) in South China (SC) during boreal summer from 1979 to 2021 were analyzed using multiple observational and reanalysis datasets. The occurrence of MHWD in SC was influenced by the tropical Indian Ocean sea surface temperature anomalies (SSTA). The study indicated significant interannual and interdecadal variability in MHWD, with a notable positive correlation between MHWD and concurrent warming in the tropical Indian Ocean. The Indian Ocean Basin Mode (IOBM) warming, which is associated with the decay phase of El Niño events, plays a crucial role in this relationship. The summer IOBM warming can reinforce and maintain the anomalous anticyclonic circulation in the mid-lower troposphere over the western Pacific through eastward-propagating Kelvin waves, intensifying the western Pacific subtropical high (WPSH) at 500 hPa. Thus, this induces anomalous low-level divergence and upper-level convergence, controlled by anomalous descending motion, which extends from the northwestern Pacific to SC. This results in suppressed convection and further increased short wave radiation reaching the surface, thereby promoting high temperatures over SC. Meanwhile, the anomalous southwesterly water vapor and high moist static energy (MSE) related to anticyclonic circulation anomaly may transport from the western Pacific into SC, leading to sufficient moisture over SC. Our results reveal an interannual relationship between tropical Indian Ocean SSTA and MHWD in SC, which could be beneficial to improve predictions of extreme events in relevant regions.