This study reveals a significant positive connection between autumn non-tropical-cyclone heavy rainfall on Hainan Island and the intensity of Eastern Pacific(EP)El Ni?o events.That is,the amount of rainfall in super E...This study reveals a significant positive connection between autumn non-tropical-cyclone heavy rainfall on Hainan Island and the intensity of Eastern Pacific(EP)El Ni?o events.That is,the amount of rainfall in super EP El Ni?o years is more than that in normal EP El Ni?o years.Comparing EP El Ni?o years of different intensities,the cooler sea surface temperature in the northwestern Pacific during super EP El Ni?o years stimulates a negative surface latent heat flux(LHF)anomaly and abnormal anticyclonic circulation at 850 hPa.Under these conditions,an abnormal zonal vertical circulation develops in the northern South China Sea once a positive LHF anomaly and abnormal cyclonic circulation(ACC)at 850hPa occur in the Beibu Gulf.The abnormal zonal vertical circulation further strengthens the ascending motion over Hainan Island,as the critical factor that leads to excessive rainfall.Further analysis shows that the positive LHF anomaly,which can be attributed to the increased latent heat transfer which resulted from the increased surface wind speed,is an important trigger for the ACC.However,the ACC is also the supplier of favorable moisture conditions because it intensifies vapor convergence over Hainan Island and meridionally transports moisture from the South China Sea to northeastern Hainan Island,thereby generating heavy rainfall.This paper emphasizes that the impact of El Ni?o events,especially super El Ni?o events,on rainfall over Hainan Island cannot be ignored,even if the traditional view is that frequent rainfall occurs mainly in La Ni?a years.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.41975008)Key Laboratory of South China Sea Meteorological Disaster Prevention and Mitigation of Hainan Province(Grant No.SCSF201906)。
文摘This study reveals a significant positive connection between autumn non-tropical-cyclone heavy rainfall on Hainan Island and the intensity of Eastern Pacific(EP)El Ni?o events.That is,the amount of rainfall in super EP El Ni?o years is more than that in normal EP El Ni?o years.Comparing EP El Ni?o years of different intensities,the cooler sea surface temperature in the northwestern Pacific during super EP El Ni?o years stimulates a negative surface latent heat flux(LHF)anomaly and abnormal anticyclonic circulation at 850 hPa.Under these conditions,an abnormal zonal vertical circulation develops in the northern South China Sea once a positive LHF anomaly and abnormal cyclonic circulation(ACC)at 850hPa occur in the Beibu Gulf.The abnormal zonal vertical circulation further strengthens the ascending motion over Hainan Island,as the critical factor that leads to excessive rainfall.Further analysis shows that the positive LHF anomaly,which can be attributed to the increased latent heat transfer which resulted from the increased surface wind speed,is an important trigger for the ACC.However,the ACC is also the supplier of favorable moisture conditions because it intensifies vapor convergence over Hainan Island and meridionally transports moisture from the South China Sea to northeastern Hainan Island,thereby generating heavy rainfall.This paper emphasizes that the impact of El Ni?o events,especially super El Ni?o events,on rainfall over Hainan Island cannot be ignored,even if the traditional view is that frequent rainfall occurs mainly in La Ni?a years.
