宜蘭南澳水龍捲之分析

本文分析2010年08月16日於宜蘭南澳所發生之水龍捲個案，作者利用拍攝到之水龍捲照片及花蓮雷達資料探討水龍捲之成長與積雲（母雲，parent cloud）間之相關。使用照相測量法(photogrammetry)可求得照片上水龍捲之仰角及方位角，再利用雷達回波所提供之距離及積雲之移動速度，可求得水龍捲的位置、直徑及高度等數值。分析結果顯示水龍捲之成長至消散與積雲的發展階段有密切的關係，當母雲於發展期時水龍捲之漏斗雲(funnel cloud)形成，母雲發展達成熟期時水龍捲達最強且直徑可達40公尺，之後當母雲進入消散期時水龍捲很快消散。水龍捲路徑分析顯示前期之路徑跟隨母雲的方向移動，但後半期路徑偏離母雲，猜測是積雲於消散期時下衝流變強且面積加大，迫使上升氣流區域外移使得水龍捲的移動路徑產生偏移。作者利用有限之資料首次對台灣地區的水龍捲做較深入的分析，結果有助於瞭解此類劇烈天氣系統的發展與積雲之間的關係，進而可為預報之參考。

關鍵字

水龍捲；龍捲風；漏斗雲；照相測量法；積雲對流；下衝流

並列摘要

A waterspout observed on 16 August 2010 near YiLan NanAo is presented. A sequence of waterspout pictures combining with the Hua-Lain radar data were used to study the waterspout development and its parent cloud. The photogrammetry technique was applied to compute the elevation and azimuthal angles of the waterspout. Using the radar echo, the distance from the photo site to the parent cloud was computed. Accordingly, the size and height of the waterspout were obtained. Result has shown close relationship between the waterspout development and the growth of its parent cloud. The funnel cloud was formed during the cumulus developing stage and then intensified as a fully developed waterspout while the parent cloud reached it mature stage. Subsequently the waterspout dissipated while the parent cloud was dissipating. The track of the waterspout followed it parent cloud at the beginning stage. However, the track deviated to the right of the patent cloud at the later stage. A hypothesis of this deviation was due to the downdraft occupying larger the sub-cloud area of the cumulus cloud pushing the updraft core to the periphery area that resulted in the waterspout deviated its track. This is the first detail waterspout study in Taiwan area using very limited available data. The results will advance our understanding of the relationship between a developing waterspout and its parent cloud which may benefit to the weather forecast.

並列關鍵字

waterspout ； tornado ； funnel cloud ； photogrammetry ； cumulus convection ； downdraft

國際替代計量

宜蘭南澳水龍捲之分析

全文下載

主題瀏覽