本計畫為三年計畫 (2019 August-2022 July) 為整合計畫『台灣區域豪雨預報實驗』Taiwan-Area Heavy-rainfall Prediction Experiment (TAHPEX) 的子計畫，將使用區域模式 (HWRF)及全球模式 (MPAS) 模擬台灣地區伴隨梅雨與颱風的劇烈降雨，並與Taiwan-Area Heavy-rain Observation and Prediction Experiment (TAHOPE)在2020年5至9月實驗觀測資料比對。模式2公里高解析度將集中於台灣附近地區，可以將中央山脈伴隨梅雨與颱風的強對流有較好的解析。模擬比較含HWRF (18-6-2 km, 三層槽狀)以及MPAS (60-10-2 km, 三個焦段) 將於第一年（2019年8月起）進行。同時，也將利用GSI/hybrid 將福衛七號掩星資料同化於HWRF與MPAS，了解對2019年8月以後颱風預報的影響。在第二年（2020年8月起），著手進行HWRF與MPAS的相對預報表現之比較，並利用GSI/hybrid將TAHOPE大部分觀測資料同化。我們將進行梅雨與颱風系統的渦度及位渦收支的動力診斷以及動量與角動量平衡分析，了解颱風路徑與系統對流演變的重要特性。同時，我們將探討不對稱量位渦收支以闡明改變位渦趨勢的各種動力如何導引颱風移動以及路徑偏折。最後一年（2021年8月起），利用TAHOPE完成的再分析場用來了解實驗觀測資料、地形作用與海洋作用對HWRF劇烈降雨預報的影響。第二年起，我們亦將利用NCEP FV3全球模式，並與MPAS比較在台灣地區相似高解析度的2018-2022實際颱風個案預報。本計畫主要目標在彰顯目前高解度模式(HWRF, MPAS 與FV3)預測陡峭地形上劇烈降雨的能力，在定量上了解三者在不同降雨過程的相對優勢，俾以提供氣象局作業及模式發展的有用建議。 ;The three-year (2019 August-2022 July) project, which is a subproject of the integrated project, Taiwan-Area Heavy-rainfall Prediction Experiment (TAHPEX), will apply both regional model HWRF and global model MPAS to investigate the severe rainfall associated with Mei-yu systems and typhoons over Taiwan with the field observations collected from Taiwan-Area Heavy-rain Observation and Prediction Experiment (TAHOPE) in May-September 2020. A high-resolution area of 2-km will be targeted on the vicinity of Taiwan for better resolving intense convection accompanying the Mei-yu systems and typhoons over the steep Central Mountain Range. Inter-comparisons between HWRF (18-6-2 km, nested by three domains) and MPAS (60-10-2 km, different resolutions of three zones) will be conducted in the first year (from August 2019). The observation data will be assimilated by GSI/hybrid into HWRF and MPAS to understand the benefit of the data including FORMOSAT-7 RO data in the typhoon prediction from August 2019. In the second year (from August 2020), inter-comparisons among HWRF and MPAS will be conducted with GSI/hybrid to assimilate most of the available observation data in 2020. Dynamic diagnostics including vorticity and potential vorticity budget analyses as well as momentum and angular momentum dynamic balance will be conducted for exploring the essential features of the evolving convection associated with the typhoon systems. Asymmetry decomposition of PV budget will be analyzed for both model simulations to highlight the relative role of each dynamic forcing involved in PV tendency in steering the typhoon movement and track deflection. In the third (last) year (from August 2021), the reanalysis data from TAHOPE will be utilized to understand the impact of the experimental data, topographic effect and ocean effect on the HWRF regional model prediction. For reference, NCEP FV3 global model prediction will also be conducted from the second year to provide complemental comparisons with MPAS with similar high-resolution near Taiwan area for typhoon events in 2018-2022. The important goal of this project is to realize the state-of-art capability of high-resolution regional and global models (HWRF, MPAS and FV3) in predicting severe rainfall over the steep island mountain, and better quantify their relative advantages at simulating various rainfall processes, thus providing valuable suggestions to CWB operation and model development.
