頁籤選單縮合
題名 | 2003年11月21日東部外海深對流個案研究=Case Study on Deep Convection Near the Vicinity of Green Island on November 21-22, 2003 |
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作 者 | 潘大綱; 鄭哲聖; 趙俊傑; 劉崇治; | 書刊名 | 氣象預報與分析 |
卷期 | 179 2004.06[民93.06] |
頁次 | 頁33-40 |
分類號 | 328.291 |
關鍵詞 | 海氣交互作用; 冰雹; 都卜勒雷達; Air-sea interaction; Hail; Doppler radar analysis; |
語文 | 中文(Chinese) |
中文摘要 | 深對流活動由於經常伴隨有顯著的天氣現象,如雷雨、冰雹、亂流、下衝風等,對飛航安全威脅甚鉅。本省深對流發生主要分布於初春及梅祭季,其影響範圍時間長,夏季在熱力作用影響下,也有局部地區之對流發展,但範圍與影響均不及前者。普遍而言,臺灣地區在10月份以後深對流活動才漸漸減少;2003年11月21日在臺灣東部外海發生了一系列之深對流,此對流高度從衛星上估算將近四萬呎,另從飛機觀測資料顯示,飛機於二萬四千呎仍無法出雲,且遭遇不同大小之冰雹及閃電。 分析此一個案之環境場發現,深對流之發展似與中緯度之系統無直接明顯之關聯,但鋒面通過臺灣地區後,中央山脈地形阻擋所成之低層輻合為激發對流的重要條件之一。 綠島探空分析CAPE值為1147m2s2,顯示當時大氣條件有利深對流發生,雷達與及衛星資料分析產生冰雹之深對流胞,在都卜勒徑向風資料中顯示,深對流中有顯著輻合特徵,此一輻合在結冰高度以上,深度約有三公里。另海溫分析亦如當日之海溫達攝氏28度,從衛星推估之海氣交互作用OPI(Objective Potential Index)指數亦高達0.7,顯示海氣作用相當旺盛。分析資料顯示,當對流系統往東移離開此一高OPI值區且脫離地形影響下之低層風切區後,對流即迅速減弱。 |
英文摘要 | This research is a preliminary study focusing on the large scale surrounding conditions and in-storm characteristics of a series of deep convective activities near the vicinity of Green Island on Nov. 21-22, 2003. Sporadic deep convective activities persistently appeared at the southeastern end of a banded convection. Average height of the band reaches 24000 ft while deep convection overshoots to 40000 ft. Aircrews reported various sizes of hail when they penetrated one of several convective embryos. Our analyses results suggest that the passing front associated with the meso-scale topography generates a low-level shear line, serving as a triggering mechanism favorable for deep convection initiation. Proximity soundings and OPI calculation also signifiy that the atmosphere possessed robust air-sea interaction. The CAPE of GI in the morning of Nov.21 reads to 1147 m2s2 indicates the atmosphere has a convective unstable in nature. The in-storm characteristics of the specific hailstorm that aircrews flew in were reanalyzed using GI Doppler radar data. A strong mid-layer convergence with 3 km depth centered at 6 km AGL near freezing level was observed. This feature powerfully suggests that strong vertical motion, rapid recycling of the ice embryos under humid surrounding is conducive to hail growth. Convections die down quickly as they move out of the low-level shear area and small OPI region. |
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