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<p>Ocean-atmospheric interactions are known to be crucial for the prediction of genesis and intensification of tropical cyclones (TCs). The TCs are the most catastrophic natural disasters threatening livelihood and socioeconomy, which are abruptly altered by regional climate variability. The present study investigates the cascading impacts of an extreme positive Indian Ocean Dipole (PIOD) event of 2019 on the severity and frequency of TCs and marine heatwaves (MHWs) in the Arabian Sea. During the extreme PIOD phase, anomalous easterly winds enhanced SST zonal gradients in the tropical Indian Ocean, triggering a downwelling equatorial Kelvin wave, which was further intensified by the reflection of Rossby wave from the African coast, thereby contributing to increased MHWs and TC activity. This study highlights that the Arabian Sea in 2019 experienced an anomalously high SST, marking the first historical record by exceeding its dipole mode index value of 2.1&#xa0;°C; subsequently attributed to high MHW frequency (9 events) and five TC occurrences. A prolonged occurrence of surface and subsurface MHWs is observed prior to the TCs. The vertical coupling between surface and subsurface MHWs regulates the thermal structure of the upper ocean and, in turn, modulates TC activity in the Arabian Sea. Furthermore, a bimodal pattern of subsurface MHWs with pronounced warm anomalies was observed during the pre-monsoon (March-May) and post-monsoon (October-December) periods, indicating two distinct phases of subsurface heat accumulation and persistence in the Arabian Sea. The decreased vertical wind shear and low-level jet are favorable for the prolonged sustenance of MHWs and TC activity during the onset of monsoon. The findings provide insights into the synergistic interplay of extreme PIOD event associated MHW, TCs, and their implications for regional climate variability during 2019.</p>

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Back-to-back triggering of tropical cyclones during extreme positive IOD event in the Arabian Sea

  • 期刊论文

  • 发表日期：

    2026年1月6日

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  • Amit Kumar Jena,
  • Manasa Ranjan Behera,
  • Sachiko Mohanty,
  • V. K. Srineash

摘要

Ocean-atmospheric interactions are known to be crucial for the prediction of genesis and intensification of tropical cyclones (TCs). The TCs are the most catastrophic natural disasters threatening livelihood and socioeconomy, which are abruptly altered by regional climate variability. The present study investigates the cascading impacts of an extreme positive Indian Ocean Dipole (PIOD) event of 2019 on the severity and frequency of TCs and marine heatwaves (MHWs) in the Arabian Sea. During the extreme PIOD phase, anomalous easterly winds enhanced SST zonal gradients in the tropical Indian Ocean, triggering a downwelling equatorial Kelvin wave, which was further intensified by the reflection of Rossby wave from the African coast, thereby contributing to increased MHWs and TC activity. This study highlights that the Arabian Sea in 2019 experienced an anomalously high SST, marking the first historical record by exceeding its dipole mode index value of 2.1 °C; subsequently attributed to high MHW frequency (9 events) and five TC occurrences. A prolonged occurrence of surface and subsurface MHWs is observed prior to the TCs. The vertical coupling between surface and subsurface MHWs regulates the thermal structure of the upper ocean and, in turn, modulates TC activity in the Arabian Sea. Furthermore, a bimodal pattern of subsurface MHWs with pronounced warm anomalies was observed during the pre-monsoon (March-May) and post-monsoon (October-December) periods, indicating two distinct phases of subsurface heat accumulation and persistence in the Arabian Sea. The decreased vertical wind shear and low-level jet are favorable for the prolonged sustenance of MHWs and TC activity during the onset of monsoon. The findings provide insights into the synergistic interplay of extreme PIOD event associated MHW, TCs, and their implications for regional climate variability during 2019.