| 摘要: | 本子計畫是依據 106年度科技部自然司，防災科技學門專題研究計畫課題重點說明(氣象領域) 中的第1-3項 ，即”梅雨季豪大雨定量降水預報技術的建立與改進”課題所提出，工作內容為該課題之下的第1條:依不同時間尺度之需求，配合不同特性數值模式與/或資料同化等預報技術，發展梅雨季即時(0~3 小時)、極短至短期(3~24 小時)、逐日(1~3 日)、以至一週(3~7 日)之定量降水預報技術，並延長應變前置時間; 與第3項: 進行梅雨季區域性強降水系統受地形和西南氣流影響、觀測系統模擬實驗、以及可預報度等之相關研究。申請人近年來發展了一個新的多都卜勒雷達風場合成系統(Liou and Chang 2009, Liou et al. 2012, Liou et al. 2014)，命名為WISSDOM (WInd Synthesis System using DOppler Measurements)，此方法納入流體連續方程與渦度方程做為變分約束條件，可以同時使用來自任何數目雷達的資料，合成出涵蓋雷達baseline以及沿著複雜地形上的三維風場，這是目前國際雷達氣象學界唯一具有前述所有優點的方法，特別適合用在台灣多山的環境，並能最佳化的充份利用環台雷達網的觀測資料。本研究將配合WISSDOM所合成的風場，重新研發一個可以在地形上直接反演熱力場的運算方法，再將由風場直接觀測與反演的在地形上的氣象變數場，初始化一個高解析度的數值模式，以期改進模式在山區預報降雨的表現。此為一個三年期的計畫，分年的工作項目如下，本申請書的計畫為第三年：第一年(2016/8-2017/7)：配合由WISSDOM所合成出來的沿地形三維風場，重新研發一個可以在地形上直接反演溫度與壓力等熱力場的運算方法。第二年(2017/8-2018/7)：使用觀測系統模擬實驗(OSSE)的架構，將雷達觀測與反演得到的三維風場、溫度場、壓力場、雨水與雪水混合比，初始化一高解析度的數值模式，並驗證在此一理想的情況下，模式對於發生在山區複雜地形上豪大雨定量預報的改善程度，並根據結果對計算方法進行調整。第三年(2018/8-2019/7)：根據前二年的研究結果，將此方法用在真實個案的分析上，進行模式降雨預報表現的評估，初步規劃的目標為2008年西南氣流實驗中的個案，或是發生在大都會地區的豪大雨個案。 ;The applicant of this proposal has recently developed a new multiple-Doppler radar wind synthesis algorithm named WISSDOM (WInd Synthesis System using DOppler Measurements, see Liou and Chang 2009; Liou et al. 2012, Liou et al. 2015). This method uses continuity condition and vertical vorticity equation as two major constraints, and is capable of using data simultaneously from any number of radars to recover the three-dimensional wind fields along/near the radar baseline as well as immediately above terrain. This is so far the only algorithm in the radar meteorology community that possesses all advantages mentioned above. It is particularly suitable to recover the wind field in an environment such as Taiwan with complex topography, and can optimally uses the data collected by Taiwan’s island-wide radar network.This research will apply the WISSDOM-synthesized wind field, the retrieved three-dimensional thermodynamic (i.e., pressure and temperature) field to initialize a high resolution numerical model, and study the performance of the model in forecasting the rainfall in a mountainous region. This proposal is the third part of a three-year project, and the goal of each year is listed in the following:1st year(2016/8-2017/7): To better use the wind field following the terrain obtained from WISSDOM, we will design a new thermodynamic retrieval scheme to recover the pressure and temperature fields above the complex topography.2nd year(2017/8-2018/7): Using the Observation System Simulation Experiment (OSSE) framework, we will apply the radar observed and retrieved three-dimensional wind, temperature, pressure, rain water, snow water, all are in a domain with complex terrain, to initialize a high resolution numerical prediction model. The purpose is to examine that under this idealized scenario, the improvement of the model’s capability in terms of predicting heavy rainfall in a mountainous region. Modification of the entire algorithm will be performed if necessary, based on the results from the OSSE tests. 3rd year(2018/8-2019/7): Based on the results from the previous two years, this method will be applied to real case studies. Currently, the selected targets can be the heavy rainfall cases from 2008 SOWMEX/TiMREX, or the intensive rainfall cases occurring in a metropolitan area such as the Taipei city. |
