本論文針對2015 年6 月14 日台北都會區豪雨型午後雷暴進行觀測與特徵分析，主要發現有：(1) 豪雨型午後雷暴的特徵為短延時強降雨，伴隨顯著對流胞的合併，胞合併不僅加大對流面積，也顯著增 大強回波厚度。(2)有利胞合併之環境條件主要為強化的低層輻合場，在本個案中強化的低層輻合是由潮 濕的海風環流和稍早對流降雨蒸發所導致的冷池-外流邊界所形成。(3)胞合併前後雙偏極化雷達參數產 生顯著變化，包括Zdr 的柱狀結構，為正且大值之Zdr 往上延伸超過融解層2～3 公里，是混合態水象 粒子存在的特徵，和強上衝流密切相關。Kdp 也呈現柱狀結構，和回波反射率有很好的相關，有潛力成 為劇烈降雨的預報指標。低層Kdp 和劇烈降雨強度有很好的相關，表示Kdp 是很好的定量降雨估計的 參數。本論文最後也針對豪雨型午後雷暴的可預測度問題進行討論。

In the paper, observational characteristics of urban flash flood in Taipei basin associated with afternoon thunderstorm of 14 June 2015 are examined. The major findings include: (1) urban flash flood associated with afternoon thunderstorm is characterized with extreme rainfall intensity with short duration and is closely related to the merge of severe convective cells. The merge of convective cells produces enlarged precipitation area and strong echoes which can extend to a much higher altitude. (2) Enhanced horizontal convergence produced by the sea breeze circulation and cold outflow from earlier developed storms is favorable for cell merge. (3) Significant variations on the structure and distribution of polarimetric variables before and after cell merge are identified. Column of Zdr extended 2~3 km above the melting layer is the manifestation of mixed phase hydrometeors existence and indicative of strong updraft. The appearance of Kdp column suggests potential of heavy rainfall and can be served as a good index for quantitative precipitation estimation. Predictability of urban flash flood complex storms and its implication for nowcasting is also discussed.