Effects of Microphysical Latent Heating on the Rapid Intensification of Typhoon Hato(2017)

A 72-h cloud-resolving numerical simulation of Typhoon Hato(2017)is performed by using the Weather Research and Forecasting(WRF)model with the Advanced Research WRF(ARW)core(V3.8.1)on a horizontal resolution of2 km.To enhance the background tropical cyclone structure and intensity,a vortex dynamic initialization scheme with a terrain-filtering algorithm is utilized.The model reproduces reasonably well the track,structure,and intensity change of Typhoon Hato.More specifically,the change trend of simulated maximum wind speed is consistent with that of best-track analysis,and the simulated maximum wind of 49 ms^-1 is close to that(52 ms^-1)of the best-track analysis,indicating that the model has successfully captured the rapid intensification(RI)of Typhoon Hato(2017).Analyses of the model outputs reveal that the total microphysical latent heating of the inner-core region associated with enhanced vertical upward motion reaches its maximum at 9-km height in the upper troposphere during the RI stage.The dominant microphysical processes with positive latent heat contributions(i.e.,heating effect)are water vapor condensation into cloud water(67.6%),depositional growth of ice(12.9%),and generation(nucleation)of ice from vapor(7.9%).Those with negative latent heat contributions(cooling effect)are evaporation of rain(47.6%),melting of snow(27.7%),and melting of graupel(9.8%).Sensitivity experiments further show that the intensification speed and peak intensity of this typhoon are highly correlated to the dominant heating effect.A significant increase in graupel over 5-10-km height and snow at 10-14-km height in the inner-core region of Typhoon Hato corresponds well with its RI stage,and the latent heating from nucleation and depositional growth is crucial to the RI of simulated Hato.