華南地區中尺度對流系統環境之分析研究

The Analysis of Environmental Conditions Associated with Mesoscale Convective Systems in SE China

朱昌敏(Chang-Min Chu) ； 陳景森(Ching-Sen Chen)

《大氣科學》 16卷4期 (1988/12) Pp. 349-371

摘要

每年的五、六月梅雨期，常有組織性中尺度對流系統（Mesoscale Convective System；MCSs）在華南地區生成且伴隨鋒面帶向東移行發展，進而在華南、臺灣等地區造成大量降水，甚至有豪雨災變天氣的發生。因此，本文依據中央氣象局所提供之IR衛星雲圖與綜觀測站之觀測等七個案例的資料，藉由Barnes（1964, 1973）的客觀分析方法，依熱力與動力因素選取定性的相當位溫（θe）、定量的相當位溫梯度（|∇н θe|）及鋒生函數之輻散與變形項和、溫度平流與水汽輻合、地面至700 mb垂直平均風切、穩定指數與可降水量等七項分析因子，對華南地區環境之演變情形進行分析比較，結果顯示這些分析因子之交集區域與豪雨發生地區有很高的相關性，這或許能提供豪雨預報的參考。本文僅從這七個案例中，選取較具有代表性的兩個案例作分析比較，最後再將這兩個案例與其他五個案例之總結部分一併討論，以印證這些分析因子之可行性。

關鍵字

梅雨 ； 中尺度對流系統環境

並列摘要

Several mesoscale convective systems (MCSs) took place in SE China during Mei-Yu season. If the systems would last long enough, it might dump a lot of rain in Taiwan area. Therefore the forecast of the occurrence of MCSs is an important work. We will analyze the environmental conditions associated with MCSs in seven cases. One group of these seven cases has significant organized cloud over (diameter ＞ 400 Km) and MCS system. Another group have to significant organized cloud system (diameter ＜ 400 Km). They were (1) May 27-28, 1981 case (extensive MCS cloud cover in SE china and a lot of rainfall in Taiwan area); (2) June 17-18, 1983 case (extensive MCS cloud cover in SE China, and thunderstorms in Taiwan area); (3) May 31-June 1, 1984s (extensive MCS cloud cover in SE China, and a lot of rainfall in the evening on June 2 in Taiwan area); (4) May 15-16, 1987 extensive MCS cloud cover heavy precipitation in Taiwan area on May 17); (5) May 20-21, 1986s (no significant cloud cover in SE China, but rainfall occurred in northern Taiwan); (6) June 4-5, 1986 case (several MCSs cloud cover occur in SE China, and a lot of rainfall in Taiwan area); (7) June 14-15, 1984 case (extensive MCS cloud cover in SE China but small amount of rainfall in Taiwan area).Through the objective analysis of the every 3-hr surface data and every 12-hr upper air soundings we found some good relationship between the formation of organized MCS cloud system and the following factors: the horizontal gradient of surface equivalent potential temperature, the surface frontogenesis of divergence and deformation terms, low-level temperature and moisture convergence, surface-700mb wind shear, stability index and precipitable water. Nevertheless this analysis is premature. More cases study are needed in order to generalize this conclusion.

並列關鍵字

Mei-Yu ； MCS's environment