Correlation Between Tropical Cyclone Activity In The Northwest Pacific And Other SST Anomalies In The El Niño Decay Year

El Ni?o-Southern Oscillation(ENSO)is the most significant interannual variability signal in the climate system,and also an important source of predictability in seasonal and interannual prediction.ENSO signals can influence Tropical Cyclone(TC)activities over the Western North Pacific by influencing Sea surface temperatures(SST)anomalies in the Atlantic and Indian oceans.In this paper,based on the Tropical Cyclone Best-Track Archive from Joint Typhoon Warning Center and sea surface temperature data from Hadley center,fifth generation reanalysis data(ERA-5)from the European Centre for Medium-Range Forecasts,and marine mixed layer data from National Centers for Environmental Prediction Global Ocean Data Assimilation System,the ocean energy budget and wave flux are used.According to TC generation frequency(TCGF)in the Western North Pacific from July to October,El Ni?o attenuation events are divided into two situations.On this basis,the TC activities anomaly,environmental elements,circulation anomaly characteristics over the Western North Pacific and its association with the SST anomalies in the tropical North Atlantic and the tropical Indian Ocean are compared,and the possible causes of the SST anomalies in the tropical North Atlantic Ocean and the tropical Indian Ocean are discussed.The main conclusions are as follows:(1)In the case of less TCGF,significant negative TCGF anomalies mainly occurred in the eastern part of the Western North Pacific,which was corresponding to significant negative TC generation index(MWGPI)anomalies.The contribution of positive vertical wind shear anomalies was the largest,and TC activities was inhibited.In this case,Western North Pacific Anomalous Anticyclone(WNPAC)existed all year round.In the case of more TCGF,TCGF significant positive anomalies mainly occurred in the South China Sea and the vicinity of the Philippines,relative humidity contributed the most,and the frequency of landing in China increased,especially in Guangdong,Fujian and other coastal areas,TC activity was significantly enhanced.After August,WNPAC turned to anomalous cyclonic.(2)Under the two conditions,there are significant differences in the SST anomalies of each basin.In the case of less TCGF,the positive SST anomalies in the equatorial Eastern Pacific reaches its peak in winter,and the positive SST anomalies in the tropical North Atlantic and Indian Ocean reaches its peak during spring while El Ni?o decays and maintains until October.In the case of more TCGF,the SST anomalies in the equatorial Eastern Pacific are similar to the case of less TCGF,and the combination of SST anomalies in the tropical North Atlantic and Indian Ocean does not show warming phenomenon during spring while El Ni?o decays.(3)In the case of low TCGF,the SST anomaly associated with El Nino in the equatorial Eastern Pacific stimulates the Rossby wave train,propagates the energy to the subtropical North Atlantic.This leads to low geopotential height over the subtropical North Atlantic,and warms the tropical North Atlantic.The combined results show that the anomalous easterlies makes the upper warm water in the eastern Indian Ocean move westward,and weakens the westerly wind in the northern Indian Ocean,so that the SST anomalies in the Indian Ocean remains positive until October.In the case of more TCGF,the anomalous westerlies is abnormally weak in the tropical North Pacific and Central America,and the warn SST anomalies signal associated with El Nino in the equatorial Eastern Pacific fails to spread to the North Atlantic.The SST anomalies is mainly affected by the local ocean-atmosphere coupling effect,while the positive SST anomalies in the Indian Ocean is not obvious,which is related to the weak anomalous easterlies.