Distinct Interdecadal Change Contrasts Between Summer and Autumn in Latitude‐Longitude Covariability of Northwest Pacific Typhoon Genesis Locations

다국어 초록 (Multilingual Abstract)

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°–140°E, 15°–30°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 Niña‐teleconnected warming. However, neither condition occurs in summer, highlighting the importance of seasonal difference in climatological background when interpreting climatic changes in typhoons.
The abrupt increase in quasi‐annual‐mean covariability between latitude and longitude of the Northwest Pacific (WNP)‐mean tropical cyclogenesis location (TCGL) since 1998 has been reported previously. However, the seasonality of interdecadal changes in such a relationship and the associated physical mechanisms remain unclear. Here, we found that the latitude‐longitude covariability in WNP‐mean TCGL of typhoons has experienced seasonally distinct interdecadal shifts since 1998, which weakened in summer and strengthened in autumn, respectively. Two reasons are proposed for this phenomenon. First, significant westward shifts of WNP‐mean TCGL exists in both seasons, due mainly to the enhanced zonal sea surface temperature (SST) gradient across the tropical western‐central Pacific induced by the interdecadal La Niña‐like tendency since 1998. Second, a robust poleward shift of WNP‐mean TCGL occurs only in autumn, attributed largely to the increase in SST over 125°–140°E, 15°–30°N. Two main factors are responsible for this SST warming: the interdecadal trend of local SST and the Central Pacific La Niña‐like teleconnection during autumn.



Distinct seasonal interdecadal changes in latitude‐longitude covariability of Northwest Pacific (WNP)‐mean tropical cyclogenesis location (TCGL) are detected

Northward and westward shifts of WNP‐mean TCGL since 1998 only co‐occurred in autumn, with the subtropical WNP sea‐surface temperature (SST) warming as the linchpin

Both the Central Pacific La Niña and local interdecadal SST trend contributed to the subtropical WNP sea‐surface warming


Distinct seasonal interdecadal changes in latitude‐longitude covariability of Northwest Pacific (WNP)‐mean tropical cyclogenesis location (TCGL) are detected
Northward and westward shifts of WNP‐mean TCGL since 1998 only co‐occurred in autumn, with the subtropical WNP sea‐surface temperature (SST) warming as the linchpin
Both the Central Pacific La Niña and local interdecadal SST trend contributed to the subtropical WNP sea‐surface warming