本研究調查了2020年5月21日至23日，臺灣地區所經歷的一次破42年梅雨季紀錄之極端降水事件（Y20R事件）。此次降水事件的成因主要與多個天氣系統之間的交互作用有關。2020年梅雨季前段，西北太平洋副熱帶高壓異常強大，導致西南季風顯著增強，從而加強了南海與中南半島一帶往東亞地區的水氣傳輸。在強烈的季風影響之下，於青藏高原東南側形成的西南渦（SWV）向臺灣方向移動。當SWV通過臺灣北側海面時，它提供了臺灣附近的潮濕渦旋環境，其底層的西北風與西南季風在臺灣海峽中部匯合，形成了有利於鋒面生成的動力和熱力條件，進而增強了海峽上的鋒面活動。這一過程中，SWV的位置則會影響鋒面生成的位置，而鋒面的位置又對降水強度影響甚大，當鋒面位於臺灣南部雨區的北側時，會顯著增加該地區的降水量。最後，觀測系統模擬實驗的結果顯示，在預報系統中加入南海北部的投落送資料可以提升對南海地區風場和水氣場的初始條件，從而改善臺灣，尤其是臺灣南部地區的強降水預報能力。本研究對理解臺灣梅雨季降水的形成機制以及大尺度背景場(2020年環境場)和中尺度天氣系統(SWV)之間的交互作用具有重要意義，並對提升極端降水事件的預報能力提供了一個參考方案。未來的研究可以擴大範圍，包含更多類型的降水事件，以便深入瞭解其降水機制。

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