Numerical models frequently encounter challenges in forecasting typhoon precipitation, particularly in areas characterized by intricate topographical features. In this study we added turbulent orographic form drag (TOFD) to the GRIST (Global-to-Regional Integrated Forecast SysTem) model to improve the accuracy of numerical models in predicting typhoon precipitation. The revised model is verified by a case study on Typhoon "Hagupit," which made landfall in Zhejiang, China, in 2020. The addition of TOFD corrected, to some extent, deviations in typhoon landfall time, landfall location, movement speed, and intensity that occurred during the model integration process. This improved the model's prediction of the amount of typhoon rainfall. After the introduction of TOFD, compared to the CTL experiment, the typhoon has a stronger warm core structure, enhanced low-level radial inflow, and enhanced low-level upward motion, accompanied by more active and more extensive low-level convection, which contribute positively to the better simulations of Hagupit's precipitation.
Lin et al. (Wed,) studied this question.