Interdecadal change in typhoon genesis condition over the western North Pacific.

The interdecadal changes in typhoon (categories 1-3) frequency and its genesis condition over the western North Pacific during the period of 1979-2011 are investigated with consideration for discrepancies among best track datasets. To tide over data uncertainty, a detection-produced dataset is utilized as a homogeneous dataset with five available best track datasets. Typhoon experienced interdecadal changes around the mid-1990s and the mid-2000s in their genesis conditions. Even under the oceanic warm state, typhoon frequency has decreased since the mid-1990s, showing a northwestward movement of its genesis location over the main formation region. The eastward gradient of vertical wind shear is the most significant factor for the change in typhoon genesis condition in recent decades. The vertical wind shear behavior is strongly linked with zonal asymmetry of local SST. We demonstrate that a westward gradient of local SST is the most important modulator of the recent typhoon behavior through the movement of favorable genesis location. The present results indicate that the horizontal distribution, not magnitude, of local SST can be a key factor for prediction of future typhoon activity, thus contributing to natural disaster mitigation and climate change adaptation strategies. [ABSTRACT FROM AUTHOR]