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題名 | 長生命期鋒面雨帶之研究(1): 軌跡分析與熱動力結構 |
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作者 | 楊淑蓉; 陳臺琦; 林沛練; | 書刊名 | 大氣科學 |
卷期 | 23:3/4 民84.09-12 |
頁次 | 頁407-447 |
分類號 | 328.63 |
關鍵詞 | 臺灣中尺度實驗; 梅雨鋒面; 鋒面雨帶; 軌跡分析; Frontal rainband; Mei-yu front; Trajectory analysis; TAMEX IOP#13; |
語文 | 中文(Chinese) |
中文摘要 | 在梅雨期間常有長達十數小時之降水系統發生在鋒面附近,而維持雨帶長生命期之機制迄今尚未完全明瞭,對IOP #13而言,此個案在其長達二十幾小時的生命史中,分別於臺灣的中、南部地區形成了三個累積雨量高達200 mm/day以上的大降雨區。此緩慢移動的雨帶系統期長生命期的特徵與生命史的演化,皆與快速移動之颮線、雷雨系統等不盡相同,而且該個案之天氣條件與一般認知之梅雨鋒面大不相同,是梅雨期中較特殊之案例。 由持續近兩小時之回波結構演化和合成風場分析證明,此系統隨時間變化很小,動力結構十分穩定。除了在最底層有微弱之鋒面輻合外,此系統之西北緣和一般颮線之對流區結構相同,而此系統之東南側和颮線之層狀區類似。即低層之西風入流及西南入流相遇輻合所形成之風切線位於主要降水區之西北緣,中高層之低壓及低壓之高壓所產生之氣壓梯度力可持續引領主要來自西側及西南角之暖濕空氣,維持上沖流之強度及位置,而中高層之垂直風切可保持此傾斜之上沖流和下沈氣流及強回波區在三維空間上錯開,而有利於系統之持續發展。 以上之結構由氣塊軌跡以及熱動力反求結果可以得到印證,所以IOP #13的雨帶內部運動結構雖與一般常見之鋒面雨帶上沖流位置配置十分不同,但在環境與內部熱動力條件配合良好下,仍可維持極長之生命期。至於此雨帶系統氣壓配置之動力機制及移動方式將於第二部份中討論。 |
英文摘要 | In past Mei-Yu Seasons there are many long-lived systems evolving near the front, however the mechanisms to maintain these systems are not very clear yet. For TAMEX IOP # 13 case, a long-lived rainband had precipitated near 200 mm/day in three areas within Taiwan vicinity in its almost one day long life. The characteristics of its structure and life cycle of this slow moving system is very different with the fast moving squall line in the same season. From two hours continuous analysis of the kinematic, thermodymic and the reflectivity fields, the results show that the dynamic structure of this system was very steady. The trajectories calculation provided a vivid illustration of the dynamic structure, the northwest edge was very similar to the leading edge of the convective region of a squall line. The low level west and southwest inflows form this northeast-southwest orientated shear zone on the northwest edge. The west inflow encountering the shear zone were lifted above the southwest inflow and form the major updraft. This updraft associated with shear zone was tilting toward east. Only near the narrow southwest tip the southwest inflow may contribute to the updraft. A low was formed in the middle levels, the pressure gradient force is helpful to bring in more moist and warm low level inflows and maintain the three dimensional unique structure and sustain this long lived system. |
本系統之摘要資訊系依該期刊論文摘要之資訊為主。