- 期刊
葛拉斯颱風（1994）及其受到台灣地形影響之研究 第一部分：觀測分析
The Effect of Taiwan Terrain on Typhoon Gladys (1994) Part I: Observational Study
摘要
本研究選取1994年侵襲台灣之葛拉絲颱風進行觀測分析及數值模擬。在第一部份中，主要是針對葛拉絲颱風之觀測資料進行分析討論，第二部份（見吳等1999）則使用GFDL颱風預報系統對葛拉絲颱風進行預報及模擬。由觀測資料結果顯示，葛拉絲颱風運動主要是沿著大尺度天氣系統外緣移動。當葛拉絲颱風移經台灣時是以西北西的方向運動，而非呈理想數值模擬所顯示之氣旋式運動軌跡，此顯示真實大氣中颱風之運動遠較理想數值模擬複雜。在葛拉絲颱風侵襲台灣期間，除對台灣北部、東北部及山區帶來較多之降水外，在台灣中南部平原及台灣東南部亦產生局部低壓之現象。由觀測分析結果顯示，在台灣中南部平原之局部低壓主要是因環境流場繞過台灣地形所導致，而葛拉絲颱風之接近會造成此局部低壓明顯加深。位於台灣東南部之局部低壓則是因葛拉絲颱風環流過山造成下沈氣流絕熱增溫所致（焚風），因此當葛拉絲移至台灣海峽時此局部低壓亦隨之消失。若由雷達回波資料及雷達反求風速之分析顯示，葛拉絲颱風為一半徑很小之颱風（其最大暴風半徑約只有15－20公里），且當葛拉絲颱風經過台灣時，除造成颱風雨帶在迎風面有因舉升加強對流之現象外，也使颱風眼及眼牆結構受到嚴重之破壞，以致當葛拉絲再度回到海面上時強度仍無法恢復。透過對葛拉絲颱風之觀測分析，除對此颱風的運動、強度及結構之演化與其受到台灣地形影響之中尺度特徵能有進一步之瞭解，並以此做為第二部份（吳等1999）的數值模擬之基礎。希望藉由觀測分析及數值模擬之探討能使我們更為瞭解地形對颱風之影響。
並列摘要
Due to the existence of the complicated terrain and the elevated Central Mountain Range (CMR) in Taiwan, significant variations of track and intensity of typhoon occur as typhoons approached the island. The interaction of a typhoon with CMR also produces significant mesoscale variations in terms of wind and precipitation over Taiwan. In this paper an observational study of Typhoon Gladys (1994) is carried out to understand the effect of Taiwan Terrain on Gladys. Numerical studies are also performed in the follow-up paper (Part II).Gladys made landfall near northeastern Taiwan (Sue-Au) at 0250 UTC on 1 September and left Taiwan near Hsin-Chu at 0600 UTC on the same day. A local low, induced by the interaction between the environmental mean flow and CMR, was analyzed to the west of CMR when Gladys crossed Taiwan. Another local low was found at southeastern Taiwan, which did not from until Gladys's main circulation reached the east coast of Taiwan. It appears that this local low was induced by the so-called föhn when the flow associated with Gladys crossed over the mountain near the eastern Taiwan and resulted in the subsidence warming of the air.The heavy precipitation associated with Gladys mainly occurred at the upwind mountain area in the northern and northeastern Taiwan. The radar echo and the retrieved wind showed that Gladys has a small eye, and the eyewall structure was changed due to the effect of Taiwan topography, thus Gladys's intensity was greatly reduced after landfall.