A possible mechanism of the impact of atmosphere-ocean interaction on the activity of tropical cyclones affecting China

Abstract

In this study, tropical cyclone data from China Meteorological Administration (CMA) and the ECMWF reanalysis data for the period 1958–2001 was used to propose a possible mechanism for the impacts of air-sea interaction on the activity of tropical cyclones (TCs) affecting China. The frequency of TCs affecting China over past 40 years has trended downward, while during the same period, the air-sea interaction in the two key areas of the Pacific region has significantly weakened. Our diagnoses and simulations suggest that air-sea interactions in the central North Pacific tropics and subtropics (Area 1) have an important role in adjusting typhoon activities in the Northwest Pacific in general, and especially in TC activity affecting China. On the contrary, impacts of the air-sea interaction in the eastern part of the South Pacific tropics (Area 2) were found to be rather limited. As both observational analysis and modeling studies show that, in the past four decades and beyond, the weakening trend of the latent heat released from Area 1 matched well with the decreasing Northwest Pacific TC frequency derived from CMA datasets. Results also showed that the weakening trend of latent heat flux in the area was most likely due to the decreasing TC frequency over the Northwest Pacific, including those affecting China. Although our preliminary analysis revealed a possible mechanism through which the air-sea interaction may adjust the genesis conditions for TCs, which eventually affect China, other relevant questions, such as how TC tracks and impacts are affected by these trends, remain unanswered. Further in-depth investigations are required.