康芮颱風（2013）侵台期間台灣西南部強降雨事件之研究

A Study on the Heavy Rainfall Event Occurred in the Southwestern Taiwan When Typhoon Kong-rey (2013) Was Affecting Taiwan

李清勝(Cheng-Sheng Lee) ； 饒心誠(Hsin-Cheng Jao) ； 謝宜桓(Yi-Huan Hsieh)

《大氣科學》 46卷2期 (2018/06) Pp. 149-171

https://doi.org/10.3966/025400022018064602002

摘要

康芮颱風(Kong-rey，2013)於8月28～29日沿台灣東部外海北上期間，台灣西南部平地地區出現顯著降雨，此降雨型態與颱風降雨氣候模式所估計者有顯著差異。雙都卜勒風場及回波顯示，當康芮中心位於台東、花蓮外海時，有一南北向線狀對流系統在台灣西南部地區形成，並維持3～4小時，為導致此特殊降雨事件之重要原因。本研究利用天氣研究和預報模式(Weather Research and Forecasting Model，WRF)，針對此線狀對流系統之形成進行模擬實驗，以探討其中之重要機制。結果顯示，在康芮中心於台東、花蓮外海期間，台灣中部沿海地區低層有一中尺度氣旋式環流形成，使西南部地區出現西北風與西風之輻合，對流系統在此地區形成與發展。逆軌跡分析結果顯示，位於台灣北側之潮濕空氣塊，受低層環流影響而以氣旋式軌跡移至西南部之輻合區，為此降雨事件的重要水氣來源。結果同時顯示，台灣地形顯著影響此對流系統之形成位置；移除地形（或地形減半）之敏感度實驗結果顯示，台灣中部沿海地區不再有（或無明顯）中尺度氣旋式環流形成，導致低層主要輻合區位置改變，使對流系統與降雨區位置和觀測有顯著差異。

關鍵字

康芮颱風 ； 颱風降雨 ； 台灣地形

並列摘要

Heavy rainfall occurred in the southwestern part of Taiwan during 28-29 August 2013 when Typhoon Kong-rey was moving northward along the east coast of Taiwan. The rainfall distribution differs significantly from that estimated using the typhoon rainfall climatology model. Dual-Doppler radar-derived wind and radar reflectivity indicated that a north-south orientated line convection formed in the southwest part of Taiwan and maintained for 3 to 4 hours when Kong-rey was located near the east coast of Taitung-Hualien. This convective system plays the critical role in causing the rainfall event. This study attempts to simulate and analyze the important process and physical mechanism leading to this heavy rainfall event using the Weather Research and Forecasting Model (WRF). Results show that a low-level mesoscale cyclonic circulation formed near the central coast of Taiwan when Kong-rey was moving northward along the east coast of Taitung-Hualien. Strong convergence of the northwesterlies and the westerlies occurred in the southwest of Taiwan where the convective system formed. Results of backward trajectory analyses show that the low-level moist air moves cyclonically from the northern outer area of Kong-rey around the Taiwan terrain to the southwestern Taiwan, which is also favorable for the formation of convection and is the major moisture source of this rainfall event. Results of the terrain-sensitivity experiments show that the terrain height of Taiwan topography affects the location where the convective system forms. In no terrain (or half terrain height) experiment, no low-level mesoscale cyclonic circulation forms at the central coast of Taiwan leading to the change of the convergence region. Thus, the locations where the convective system and heavy rainfall occur differ significantly from those of observation.

並列關鍵字

Typhoon Kong-rey (2013) ； Typhoon rainfall ； Taiwan topography