Long-term trends of typhoon-induced rainfall over Taiwan: In situ evidence of poleward shift of typhoons in western North Pacific in recent decades

A significant poleward shift of tropical cyclones (TCs or typhoons) and TC-induced storm surge in the western North Pacific has occurred in recent decades. Here we use 64 year rainfall observations around Taiwan to provide an independent evidence of the shift. We show that, due to the island’s unique location relative to typhoon tracks, TC-induced rainfall trends are significantly rising west and north of the island but are insignificant east and southeast, caused by a preference in recent decades for TCs to veer more poleward. Analyses of large-scale fields indicate that the TCs’ poleward shift is caused by the weakening of the steering flowand western North Pacific subtropical high, which in turn is due to tropic-subtropical Indo-Pacific warming and a weakened monsoon, consistent with the expansion of the tropics due to climate change.