Distinct Interdecadal Change Contrasts Between Summer And Autumn In Latitude-Longitude Covariability Of Northwest Pacific Typhoon Genesis Locations

This study investigates seasonality of interdecadal changes in latitude-longitude covariability of the Northwest Pacific (WNP)-mean tropical cyclogenesis location (TCGL). It is found that the latitude-longitude covariability in WNP-mean TCGL of typhoons has experienced seasonally distinct interdecadal shifts since 1998, weakening in summer and strengthening in autumn. Since significant westward shift of WNP-mean TCGL exists in both summer and autumn, but robust poleward shift is only detected in autumn. The linchpin of such seasonal difference is the subtropical WNP sea-surface temperature (SST) warming in the key region of 125 degrees-140 degrees E, 15 degrees-30 degrees N, where numbers of typhoons increase in autumn but not in summer. Two main factors are responsible for the SST warming in the key region: the interdecadal trend of local SST and the Central Pacific La Nina-teleconnected warming. However, neither condition occurs in summer, highlighting the importance of seasonal difference in climatological background when interpreting climatic changes in typhoons.