- 期刊
台灣北部地區1980年11月19日異常降水個案研究
Case Study of Heavy Rainfall of 19 November 1980 over Northern Taiwan
摘要
台灣北部地區冬季東北季風影響期間，常有異常降水之發生；但根據陳與劉（1981）氣候分析研究指出於台灣地區在廣泛之東北風氣流控制下，在無可辨認之綜觀尺度天氣系統伴隨情況，約有40%異常降水發生。本文即針對1980年11月19日地面在盛行之東北季風影響下，台灣北部地區中尺度異常降水之氣象條件與可能激發機制之研究。結果顯示，有利於異常降水之綜觀條件包括（1）因海陸摩擦之差異產生之低層局部輻合。（2）500mb以下之深厚潛在不穩定大氣。（3）500mb與300mb之速度輻散。而引發異常降水之機制，似為850mb東風波槽與700mb東風波脊。因為波槽與波脊移至中央山脈之西，提供了台灣東北部地區動力強迫上升運動，激發地區中尺度之異常降水。比較陳等（1980）之個案研究，顯見兩者在700mb以下之低對流層均有動力強迫上升運動，以激發中尺度對流系統發展；但1980年個案在700mb西風短槽以東產生異常降水，而本個案在東風短波脊以東發生。
關鍵字
無資料並列摘要
The heavy rainfall event over northern Taiwan during the northeast monsoon season in winter is not an uncommon phenomenon. Climatological study by Chen and Liu (1981) indicated that about 40% of all the heavy rainfall events occurred in the absence of any detectable surface weather systems over Taiwan except a broad scale northeast monsoonal flow. The present paper is to study the meteorological conditions and possible triggering mechanism for a case of mesoscale heavy rainfall over northern Taiwan which occurred on 19 November 1980 during prevailing surface monsoonal flow.Results indicate that the following conditions are favorable for heavy rainfall to occur: 1) a local surface convergence generated by the land-sea differential frictional effect, 2) a deep layer of potentially unstable air from surface to 500 mb, 3) a speed divergence at 500 and 300 mb. The triggering mechanism for the heavy rainfall appears to b e an easterly wave trough at 850 mb and an easterly wave ridge at 700 mb. Both are located to the west of the Central Mountain Range, therefore provide a dynamical forcing for upward motion to the northeast of Taiwan which triggers the mesoscale heavy rainfall over that area. This is different from a previous case study by Chen et al (1980). In that case, a 700 mb westerly short wave trough was located to the west of Taiwan although dynamical forcing for upward motion in the lower troposphere were the same for both cases.
並列關鍵字
無資料延伸閱讀
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