高解析度海氣耦合模式HWRF乃為目前美國NCEP的颱風預報區域作業模式，其加入海氣交互作用過程，可以大幅改善颱風的內核結構的演變，也因此改善了颱風強度乃至路徑預報。過去侵台颱風模擬研究，發現模式初始場、初始虛擬颱風渦旋、風暴途中附近的海洋渦流強度、地形作用以及雲物理與邊界層參數化均會對颱風強度發展及移動產生若干影響，這些因素都交織一起，構成了侵台颱風路徑與強度的可預報度(predictability)。本研究擬針對上述議題，第一年(2019年8月起)利用HWRF模擬2018侵台颱風瑪麗亞Maria及山竹Mangkhut，探討海氣交互作用及物理參數化方法(不同物理組合)對上述颱風路徑與強度的影響，透過系集預報實驗，了解颱風路徑與強度預報的發散程度(spread)。第二年則將準穩定平衡的渦旋植入HWRF模式初始場，進行系集預報實驗。第二年亦將針對2019-2020年侵台颱風，探討海氣交互作用(改變風暴路途中海洋渦流強度、深度)對颱風路徑與強度預報的影響，對颱風登陸前後或鄰近台灣時的路徑及環流變化進行位渦動力與動量診斷分析。第三年則利用前兩年的研究成果及整合技術，針對2020-2021侵台颱風，探討大尺度環境、地形及鄰近海溫分布變異，如何影響颱風路徑與風雨強度的預報敏感度及可預報度，並將與NCEP及CWB颱風作業預報進行比較。 ;High-resolution ocean-coupled model HWRF is the current typhoon operational forecast model at NCEP with air-sea interaction processes involved to better capture the evolution of the internal core structure of typhoon leading to improvement of typhoon intensity as well as track prediction. Studies in the past have shown model initial conditions, typhoon bogus vortex, ocean eddy intensity near the storm path, topographic effects, and cloud microphysics as well as PBL parameterization all contribute to more or less impact on typhoon intensification and movement, thus intricately constituting the predictability of track and intensity of typhoons impinging Taiwan. We will focus on the above issues with HWRF to simulate Typhoons Maria and Mangkhut in 2018 through ensemble forecast experiments with varying air-sea interaction and physical parameterization to understand spreading of typhoon track and intensity forecasts in the first year (from August 2019). In the second year, we will implant the quasi-balanced vortex into model in ensemble forecast experiments for typhoons in 2019-2020 with coupled air-sea interaction (changing ocean eddy intensity and depth) to explore such predictability, and will conduct PV dynamics and momentum diagnostics of the typhoon near landfall at and near Taiwan. In the third year, with the integrated earlier works, we will investigate how the predictability and sensitivity of track and intensity of typhoons in 2020-2021 are influenced by large-scale environment, topography and adjacent ocean surface temperature variations, and conduct the comparisons with NCEP and CWB operational typhoon forecasts.
