Development of a coupled atmosphere–ocean typhoon regional assimilation and prediction system for operational typhoon forecasting by the Chinese Academy of Meteorological Sciences—part I: experiments of Western North Pacific typhoons in 2016

Abstract

Typhoons can interact intensely with oceans, and the atmosphere–ocean interaction has an enormous impact on the intensity and structure of typhoons. To consider the impact of typhoon–ocean interactions, a regional coupled atmosphere–ocean system for operational forecasting of Western North Pacific typhoons is established in this paper based on a public coupled atmosphere–ocean framework and in accordance with the operational typhoon forecasting conditions and system settings of the Chinese Academy of Meteorological Sciences. The new coupled system is fully validated and used for hindcasting experiments on all typhoons in 2016. The results show that the computational cost associated with the proposed coupled system is approximately 5.33 times that of the atmosphere-only system. A comparison of the hindcasts of the 2016 typhoons using the atmosphere-only system and the proposed coupled system reveals that the use of the coupled system can obviously reduce the forecasted intensity error by approximately 10–20% but not the typhoon track error. In addition, some of the intrinsic structural characteristics of typhoons influence the effectivity of the coupled system. Specifically, when typhoons have a high intensity and a low translational speed, move in an East-West or turning direction, and are at 20°N–25°N latitude, the forecasts can be relatively significantly improved by the coupled system; otherwise, the improvement is not obvious.