ISSN 1006-9895

CN 11-1768/O4

What drives the super strong precipitation over the Yangtze-Huaihe Valley in Meiyu periods of 2020?

Laboratory for Climate Studies, CMA-NJU Joint Laboratory for Climate Prediction Studies, National Climate Center, China Meteorological Administration

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    Record–breaking rainfalls occurred over Yangtze–Huaihe River Basin (YHRB) in China during Meiyu Period (June–July, JJ) of 2020, causing severe floods and disasters. These rainfall anomalies were closely linked to the extremely strong anomalous anticyclone over the western North Pacific (WNPAC), which favored convergence of water vapor over YHRB. This study argued what have drived the record–breaking rainfalls and WNPAC in Meiyu periods of 2020. A weak Central–Pacific El Ni?o rapidly decayed in spring and developed to a La Ni?a in late summer, while sea surface temperature (SST) in the tropical Indian Ocean (TIO) and tropical northern Atlantic (TNA) was considerably high from previous winter to summer. We revealed that the weak decaying El Ni?o alone was not sufficient to maintain the strong WNPAC in JJ of 2020, whereas the long-lasted warm SST anomalies in the TIO and TNA prominently contributed to the enhancement and westward shift of the WNPAC. The TIO warming intensifies the WNPAC through the eastward propagation of Kelvin waves and/or modulating the Hadley circulation. The TNA warming can force a westward–extending overturning circulation over the Pacific–Atlantic Oceans, with a sinking branch over the central tropical Pacific, which suppresses the convection activity over there and in turn gives rise to the WNPAC. The TIO and TNA warming contributed significantly to the extremely strong WNPAC in JJ of 2020.

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  • Received:January 24,2021
  • Revised:April 08,2021
  • Adopted:April 19,2021
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