A Recent Reversal in the Poleward Shift of Western North Pacific Tropical Cyclones

Recent studies have revealed a global, poleward migration trend of tropical cyclones (TCs) in terms of annual-averaged latitude where TCs reach their lifetime maximum intensity under the global warming, to which the TCs in the western North Pacific (WNP) make the largest contribution. One existing hypothesis is that there is a linkage between poleward migration of TCs and tropical expansion associated with anthropogenic forcing. Here, we introduce a new measurement, the lifetime-averaged latitude weighted by TC destructive potential, to detect the meridional migration of the TCs over the WNP, which is more reliable and meaningful as it considers not only past data uncertainty but also public concerns. Our results show that the trend of WNP TC migration reversed during the recent warming slowing-down period (after ~1999). It is the change of regional pattern of sea surface temperature (SST) characterized by the relatively warm or cold SST pool (20°-40°N, 140°-160°E) in the WNP, which contributes greatly to the meridional migration of TCs. This mechanism is different from the existing hypothesis. The effect of regional SST on TC migration arises from its impacts on the potential intensity and the large-scale circulation in the TC-prevailing region over the WNP.