The impact of tropical SST gradient on the recent change of tropical cyclone tracks and Landfall regions over the western North Pacific

Tropical storms (TS) have strong impact on the weather and climate over the East Asia region. The change of TS frequency and intensity in response to global warming have received considerable attention, while the change in TS tracks and landfall regions have less been documented. The purpose of this study is to investigate the variation of tropical cyclone tracks and landfall regions over the western North Pacific (WNP) in recent decades. Based on the climatological TS tracks and landfall regions, TS tracks are classified into three typical tracks: westward tracks, northwestward tracks, and northeastward recurved tracks in this study. A downscaling method developed by Emanuel (2006) is adopted and modified to further investigate the relative contribution of intraseasonal oscillations (ISO) and seasonal mean flow on the TS translation speed. The results show that both the northwestward and recurved tracks have significant interannual variability. However, the frequency of recurved tracks exhibits interdecadal variability, while the frequency of northwestward tracks shows an increasing trend in autumn. This implies that the number of landfall TS over Taiwan and South China increase in autumn. The variation of tropical SST gradient plays an important role on the increasing trend of northwestward tracks through modification of TS large-scale steering flow and genesis position.