莫拉克颱風綜觀環境以及降雨特徵分析

Synoptic Environment and Rainfall Characteristics of Typhoon Morakot (0908)

周仲島(Ben Jong-Dao Jou) ； 于宜強(Yi-Chiang Yu) ； 鳳雷(Lei Feng) ； 陳永明(Yung-Ming Chen) ； 李清勝(Cheng-Sheng Lee) ； 鄭明典(Ming-Dean Cheng)

《大氣科學》 38卷1期 (2010/06) Pp. 21-38

摘要

本文針對莫拉克颱風綜觀環境特徵與降雨特性進行綜合分析整理。分析內容包括高空環流特性、低層水氣通量、季風指數、季內振盪、降雨時空分布及衛星雷達觀測特徵等。初步分析結果顯示，莫拉克颱風降雨結構呈現明顯非對稱特徵，在颱風侵台期間，南方外圍環流持續出現多條對流旺盛之雨帶，雨帶受地形舉升而出現超大豪雨，由於颱風移速特別緩慢，造成台灣南部山區之超大豪雨持續三天。綜觀分析顯示，此持續且對流旺盛之雨帶的形成，可歸因於颱風外圍環流與夏季西南季風交互作用的結果。利用七股雷達都卜勒風場反演水平風垂直分布結果顯示，南部山區發生超大豪雨的時期，和雷達反演之三公里高度旺盛西風有非常高的相關性。

關鍵字

綜觀環境 ； 西南季風 ； 莫拉克颱風0908非對稱結構 ； 移速緩慢 ； 長生命期對流雨帶 ； 超大豪雨和強西風

並列摘要

Synoptic environments and rainfall characteristics of typhoon Morakot (0908) is investigated in this paper. The paper provides: (1) large-scale environment conditions: upper air circulation patterns, low-level water vapor fluxes, monsoon index calculation, and index for intraseasonal oscillation (MJO); and (2) the spatial and temporal variation of rainfall, the mesoscale characteristics of the storm through examining the satellite images and radar reflectivity and Doppler wind patterns. The satellite images and the composite radar reflectivity maps of typhoon Morakot all showed pronounced asymmetrical structure, with south side of the storm attached with huge convective rainbands. This feature is attributed to the interaction of typhoon circulation with southwest monsoonal flows.
The torrential rainfall in the mountain areas of south Taiwan in three consecutive days during the landfall period of Morakot is closely related to the continuously-developing huge convective rainbands over the Taiwan Strait. The VAD analyses showed that the torrential rainfall over the mountain is positively correlated to the strength of the westerly winds at 3 km height upstream to the convective rainbands. This prolonged continuously-developing convective rainbands over the Taiwan Strait and the induced torrential rainfall over the mountain is attributed to the slow movement of the typhoon after it made landfall.

並列關鍵字

Synoptic environment ； southwest monsoon ； asymmetrical structure of Morakot ； slow movement ； prolonged convective rainbands ； torrential rainfall and strong westerly wind