A 44‐year mean distribution of tropical cyclone heat potential (TCHP), a measure of the oceanic heat content from the surface to the 26°C‐isotherm depth, shows that TCHP is locally high in the western North Pacific (WNP). TCHP varies on interannual time scales and has a relationship with tropical cyclone (TC) activity. The third mode of an empirical orthogonal function analysis of TCHP shows that an increase in the total number of TCs is accompanied with a warm central Pacific and cool WNP. Negative TCHP anomalies in the WNP suggest that an increase in total number of TCs results in cooling due to their passages. On the other hand, the first mode shows that the number of super typhoons increases in mature El Niño years. An increase in accumulated TCHP is related to the increase in the number of super typhoons due to long duration.

Understanding oceanic responses to typhoons and the impacts those responses have on the typhoons themselves is important so that typhoon predictions performed using numerical models and typhoon forecasts can be improved. However, in situ oceanic observations underneath typhoons are still limited. To gain a deep understanding of the oceanic response and estimate the magnitude of its impact, three profiling floats were deployed in the western North Pacific during the 2011 and 2012 typhoon seasons. The daily observations showed that the sea surface cooled by more than 2°C in typhoons Ma-on and Muifa in 2011, and typhoons Bolaven and Parapiroon in 2012. The response was different at different float locations relative to the typhoon center, that is, the response within 100 km of the typhoon center was different to the response more than 100 km from the center on the right- or left-hand sides of the typhoon track, even though the response was affected by pre-existing oceanic conditions, precipitation, and the typhoon intensity. The salinity and temperature profiles were also considerably different before, during, and after the passage of a typhoon. To determine the impacts of typhoon-induced sea surface cooling on typhoon predictions, the impacts of the four typhoons were numerically evaluated using an atmosphere-wave-ocean coupled model. The coupled model simulated sea surface cooling and the resultant increases in the central pressures caused by the passages of the typhoons reasonably well. When axisymmetrically simulated, the mean sea surface cooling beneath a typhoon decreased the latent heat fluxes by 24% to 47%. A larger cooling effect gave a larger decrease in the latent heat flux only during the intensification phase. The decrease in the latent heat flux affected the inner core structure, particularly in the inflow boundary layer and around the eyewall. The cooling effect significantly affected the track simulation only for Typhoon Muifa, which had the weakest zonal steering flow of the four typhoons. These results suggest that making more frequent typhoon observations using profiling floats, further developing oceanic analysis techniques, and improving our understanding of typhoon-ocean interactions are required to produce more accurate typhoon predictions.

Recent advances in high-performance computers facilitate operational numerical weather prediction by global hydrostatic atmospheric models with horizontal resolutions of ∼ 10 km. Given further advances in such computers and the fact that the hydrostatic balance approximation becomes invalid for spatial scales < 10 km, the development of global nonhydrostatic models with high accuracy is urgently required. The Global 7 km mesh nonhydrostatic Model Intercomparison Project for improving TYphoon forecast (TYMIP-G7) is designed to understand and statistically quantify the advantages of high-resolution nonhydrostatic global atmospheric models to improve tropical cyclone (TC) prediction. A total of 137 sets of 5-day simulations using three next-generation nonhydrostatic global models with horizontal resolutions of 7 km and a conventional hydrostatic global model with a horizontal resolution of 20 km were run on the Earth Simulator. The three 7 km mesh nonhydrostatic models are the nonhydrostatic global spectral atmospheric Double Fourier Series Model (DFSM), the Multi-Scale Simulator for the Geoenvironment (MSSG) and the Nonhydrostatic ICosahedral Atmospheric Model (NICAM). The 20 km mesh hydrostatic model is the operational Global Spectral Model (GSM) of the Japan Meteorological Agency. Compared with the 20 km mesh GSM, the 7 km mesh models reduce systematic errors in the TC track, intensity and wind radii predictions. The benefits of the multi-model ensemble method were confirmed for the 7 km mesh nonhydrostatic global models. While the three 7 km mesh models reproduce the typical axisymmetric mean inner-core structure, including the primary and secondary circulations, the simulated TC structures and their intensities in each case are very different for each model. In addition, the simulated track is not consistently better than that of the 20 km mesh GSM. These results suggest that the development of more sophisticated initialization techniques and model physics is needed to further improve the TC prediction.