The Interdecadal Variation Of The Interannual Relationship Between Tropical Cyclogenesis Latitude And Longitude Over The Western North Pacific Ocean

During recent decades,there has been an increasing occurrence of CP(Central Pacific)ENSO(El Ni?o-Southern Oscillation)events and a transition from a warm PDO(Pacific Decadal Oscillation)phase to a cool PDO phase.The impacts of the Pacific climate regime shift and a shifting ENSO on the tropical cyclones(TCs)over the Western North Pacific Ocean(WNP)have been highlighted in several studies that have investigated its influence on decadal time scales on TC frequency,intensity,and track.However,the interannual relationship between TCG(Tropical Cyclogenesis)latitude and TCG longitude over the WNP basin associated with the climate regie shift has been less studied.This study examines interdecadal changes in the interannual relationship between the TCG latitude and longitude on the extended boreal summer(May–November)over the western North Pacific Ocean during 1979–2016.The main conclusions are as follows:(1)The recent increased covaribility of TCG latitude and TCG longitude is closely associated with the transion of PDO phase,the changes of ENSO state and the variation of the sea surface temperature(SST)of tropical Indian Ocean.(2)During 1979-1997,EP ENSO events had significant influence on TCG longitude,but no significant influence on TCG latitude;During 1998-2016,CP ENSO events had significant effects on both the TCG latitude and TCG longitude.The increasing occurrence of CP ENSO events in the latter period is the main reason for the enhancement of the interannual relationship between TCG latitude and TCG longitude.(3)There is a stable and strong correlation between the TCG latitude and the strength of Hadley circulation,as well as between the TCG longitude and the intensity of Walker circulation.During 1998-2016,the correlation between CP ENSO index and the intensity of Walker circulation and the correlation between CP ENSO index and the intensity of Hadley circulation increased.The change of ENSO state regulates the interannual variation of Walker and Hadley circulation and further leads to the enhancement of the interannual relationship between TCG latitude and TCG longitude over the WNP.(4)During 1979-1997,there was a significant correlation between the TCG latitude and the SST of northern tropical Indian Ocean,while during 1998-2016,there was a significant correlation between the TCG latitude and TCG longitude and the SST of the southern tropical Indian Ocean.The CP ENSO events has a strong remote correlation with the southern tropical Indian Ocean.Therefore,the influence of tropical Indian Ocean SST on the TCG location over the WNP was mainly reflected in the SST change of the southern tropical Indian Ocean.