Impact of ocean coupling on typhoon prediction in high-resolution nonhydrostatic global model

Accurate prediction of intensity and track of typhoon is crucial to mitigate typhoon disasters. To improve typhoon forecast, the “Global 7-km mesh nonhydrostatic model inter-comparison project for improving typhoon forecast (TYMIP-G7)” has been conducted under the JAMSTEC Earth Simulator Strategic Project with Special Support. In the project, ensemble of the 5-day typhoon forecast experiments in September and October 2013 were conducted by using three nonhydrostatic global atmospheric models. Preliminary results indicate that the nonhydrostatic models significantly improve the forecast skill in terms of typhoon intensity. However, the atmospheric models used in TYMIP-G7 are not fully coupled with ocean. This study aims to investigate the impact of ocean coupling on typhoon simulation by using a nonhydrostatic global ocean-atmosphere coupled general circulation model. It was found that the forecast error of typhoon intensity ranged from - 10 hPa to 10 hPa at the forecast time of 60 hours in the coupled model. We also found that there is no marked difference in the modeled typhoon intensity at the forecast lead time of 36 hours between the coupled model and standalone atmospheric model; however, the typhoon intensity was weakened after the forecast lead time of 36 hours in the coupled model compared to the standalone model. On the other hand, the forecast error of typhoon track was not changed by ocean coupling, indicating that large scale atmospheric circulations were not changed by ocean coupling in the 5-day simulation.