• 作者： 黃清勇; 林玉郎
• 作者服務機構： 國立中央大學大氣科學系; 美國北卡羅萊納州立大學海洋﹑地球暨大氣科學系
• 中文摘要： 本文利用中尺度數值模式，探討入侵對稱地形的中尺度渦旋其環流演化過程。此數值模式包含高階邊界層參數化、雲物理過程及颱風模擬之初始化方法。為配合長時間的颱風模擬，模式平流項計算使用高精確的高階半拉格朗日法以減少數值衰減。本文理想化個案模擬結果指出，對於由東入侵地形中心的渦旋如較小型颱風，無論其快或慢，強或弱，其中心路徑於登陸中尺度對稱地形時有向南偏移現象，於過山後逐漸拉回至約原中心線。動量收支分析指出，此南偏現象最有可能為南向的非地轉氣壓梯度力分量所致。當渦旋中心登陸期間，亦受東向的非地轉氣壓梯度力分量所阻，此時在地形下游產生一副低壓中心。此副中心伴隨強烈的下坡風，此有利於渦度之生成。其隨後為移速明顯加快的原中心所取代，形成一新的渦旋中心，然後以直線繼續西移。
• 英文摘要： This study employed a mesoscale numerical model to investigate the evolution of a mesoscale vorteximpinging on symmetric topography. The numerical model consists of higher-order planetary boundarylayer parameterization, cloud microphysics and an initialization method for typhoon simulations. For longtyphoon simulation time, the numerical model employs highly accurate high-order semi-Lagrangianschemes to reduce the numerical damping. Numerical results from idealized case simulations tend to showthat a westbound vortex as in a smaller typhoon, slow or fast and weak or intense, will be deflected southwardrather than northward as it approaches the center of a symmetric topography and will then rebound slightlynorthward to its original latitude after passing the mountain. Momentum budget analyses indicate that the mechanism most probably responsible for the southwarddeflection is the southward component of the ageostrophic pressure gradient. As the vortex centerapproaches the island, it is also retarded by the eastward component of the ageostrophic pressure gradient.In the mean time, a secondary low is induced at the lee side of the mountain associated with a strongdownslope wind favorable for vorticity generation. The lee secondary low is replaced by the originalvortex center which considerably accelerates after turning around the mountain peak. The reformed lowcenter then moves straight westward at later times.
• 中文關鍵字： typhoon; deflection; westbound vortex; secondary low; downslope wind
• 英文關鍵字： --