由於熱帶氣旋在數值模式初始場中通常有結構偏大、強度較弱的問題，因此需要初始化方法修正初始場渦旋強度與結構。本研究採用Nguyen and Chen (2011)提出的動力驅動渦旋初始化方法(後續稱作NC)，此方法假設環境場氣象變數與熱帶氣旋三維本體有高度相關，透過模式短時間週期反覆積分調整氣象變數分布情形，進而產生強度與觀測相當接近之渦旋結構。我的動機為測試在具有不同特性之熱帶氣旋個案中NC渦旋初始化方法是否能有一致的模式初始場改善能力，因此選取2015年暴風半徑相當廣闊之蘇迪勒颱風進行個案分析。 我們使用版本3.3.1WRF區域模式，結果顯示相較於沒有使用初始化方法(CTRL)，NC確實能有效減少初始場中熱帶氣旋最低海平面氣壓與最大風速和觀測值之差異，且不論水平或是垂直結構亦有增強的情形。經過颱風24小時模擬結果顯示NC能夠模擬較佳的三維風場，且透過定點測站風速比較呈現NC具有改善觀測誤差的表現。另外，本研究也探討地形在渦旋初始化過程中對熱帶氣旋強度發展的影響，以及初始化方法在模式應用的限制與適用性。我們選取蘇迪勒颱風靠近台灣的時間，進行在初始時間將台灣與澎湖地形移除的測試(NCNT)。結果發現NCNT在初始化過程中才能真正增強颱風的強度，而NC因在模式積分過程中受地形影響甚至可能出現spin-down的問題，進而無法達到渦旋初始化的目的。因此我們認為當颱風靠近地形時，在執行初始化過程中須將可能影響颱風之地形因素移除，直到完成初始化後再於模擬過程中移回原始地形，數小時後透過模式動力過程能夠很快調節出颱風環流與地形之交互作用。最後，我們透過不同雲微物理參數化討論不同雲微物理過程對熱帶氣旋的影響，結果顯示暖雲方案模擬出較寬廣的風場特徵與回波範圍，此結果驗證Fovell et al. (2016)提出的熱帶氣旋雲物理過程，然而微物理參數測試結果以有考慮冰相過程之微物理參數化模擬之颱風結構較接近真實情況。;In our research, a vortex initialization scheme developed by Nguyen and Chen (2011, 2014), hereafter referred as NC scheme, to construct better tropical cyclone structure at the model initial conditions using WRF through a series of 1-h integrations is used. The basic assumptions are: 1) at the model initial time, the TC structure and intensity are related to environmental conditions; 2) the TC environment does not change drastically in the short period (~1 h). We choose the case of typhoon Soudelor (2015) due to the large radius of the maximum wind speed for examining the performance of the NC scheme. This study has focused in three separate parts including impacts of the NC scheme on the open ocean, the initialization process using the NC scheme under the influence of terrains, and the impacts of microphysical process on TC initialization. The results show that the initial intensity, horizontal and vertical structure of TC Soudelor in the model are improved after using the NC scheme. Furthermore, when the TC is close to terrain, removing terrains is more effective than including the terrains during the initial spin-up process(NCNT), and the result is better than the initial state with terrain. Finally, different microphysics schemes are employed during the initialization. It is showed that the wind field close to surface with warm cloud process are stronger than the wind field with ice process included, resulting in stronger outflow and bringing more precipitation particles to the outer core increasing the radial extent of TC. The result could be corresponded to the distribution of the maximum reflectivity, and verified by the explanation proposed by Fovell et al. (2016).
