軒嵐諾颱風(2022)路徑演變之動力探討

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Title:	軒嵐諾颱風(2022)路徑演變之動力探討
Authors:	陳品閎;Chen, Pin-Hong
Contributors:	大氣科學學系
Keywords:	藤原效應;位渦收支
Date:	2024-07-24
Issue Date:	2024-10-09 14:45:52 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究使用WRF模式模擬軒嵐諾颱風(2022)之路徑演變以及其動力過程。在初期階段，颱風路徑受到高壓西南側駛流影響因此向西穩定地移動，再由於與東南側之熱帶性低氣壓產生交互作用即藤原效應，因此軒嵐諾路徑轉變成朝西南方向移動。而當熱帶性低氣壓最終合併於軒嵐諾時，造成颱風移動停滯且強度增強，此時颱風環流也比合併前還要寬廣，並且在颱風南側及東側之風速逐漸變強許多，造成颱風內往北之分量明顯增多，以及在大環境駛流引導下，導致颱風朝北移動。本研究探討熱帶性低氣壓合併於軒嵐諾時的水平環流及垂直結構，由水平環流顯示當合併過程中熱帶性低氣壓逐漸合併於軒嵐諾北側，而因熱帶性低氣壓引進西南風，因此逐漸增強軒嵐諾南側，結合上述兩種因素導致軒嵐諾在合併後環流變得相當廣。由垂直結構顯示合併時是由中層開始逐漸影響於底層，並破壞颱風之徑向風結構，導致颱風靠近熱帶性低氣壓一側之風速變得較弱許多，而合併之後其迅速變得強許多，藉由求解Sawyer-Eliassen(SE)方程式，顯示非絕熱加熱項主宰徑向風及垂直速度，而底層則由動量項提供上升氣流及徑像入流。而由位渦收支分析，指出合併前後皆由水平平流主導颱風移動，然而在合併時非絕熱加熱項逐漸增大，與水平平流項互相抵消，導致軒嵐諾移動方向及速度受到改變。而渦流運動產生平均徑向渦流位渦之平流主導了眼牆及高層大氣之位渦趨勢，因此渦流運動對於位渦趨勢是較為重要。而從地形及水氣敏感度實驗中，移除台灣及菲律賓地形以及改變颱風南側水氣量皆對颱風之路徑北轉有不同程度的影響。理想化雙渦旋敏感度實驗則顯示在有無背景風下，雙渦旋不同距離之風場結構及路徑在藤原效應下皆有不同結果。 ;This study uses the WRF model to simulate the track evolution of Typhoon Hinnamnor (2022) and explore the dynamic processes associated with the track changes. At the earlier stage, the typhoon moves westward as influenced by the steering flow southwest of the subtropical high. Then, due to interactions with a tropical depression (TD) to the southeast of the typhoon, the Hinnamnor’s track is shifted southwestward as a result of Fujiwhara effect. The TD eventually merges with Hinnamnor, leading to the typhoon′s stagnation and intensification. The typhoon circulation is gradually enlarged with stronger flow at the south and east flanks of the typhoon vortex, resulting in a noticeable northward component that drives the typhoon northward. This study explores the horizontal circulation and vertical structure of the typhoon in interaction with the TD. Wavenumber-one Potential vorticity (PV) budget analysis indicates that contributions from diabatic heating largely increase to counteract the horizontal PV advection, as a primary factor for the typhoon to move southward, and the eddy radial advection of eddy PV dominates the PV tendency. Sensitivity experiments conducted with removal of nearby Taiwan and Philippines terrain and the upstream water vapor reduction to south of the typhoon exhibit their different impacts on the typhoon′s northward track deflection.
Appears in Collections:	[Department of Atmospheric Sciences and Graduate Institute of Atmospheric Physics ] Department of Earth Sciences

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