本研究目的在分析季風環流圈中之熱帶氣旋形成過程。分析NCEP-FNL網格資料及紅外線衛星雲 圖顯示，2000〜2009年間於西北太平洋形成之290個熱帶氣旋中，共有10個熱帶氣旋於季風環流圈中 形成，佔所有個案之3.4%。在所分析之6個水平尺度大於2500公里的季風環流圈中，每個季風環流圈 皆有兩個低壓擾動先後於季風環流圈之西側與東側形成，若無其他不利因素影響，兩者將於48小時內 先後形成熱帶氣旋。所分析之10個熱帶氣旋中，其中8個個案屬單一季風環流圈中所形成之雙熱帶氣 旋之一；其餘2個個案則屬一個季風環流圈形成單一熱帶氣旋之類型。結果亦顯示，於季風環流圈中所 形成之熱帶氣旋常有較大之暴風半徑。 本研究亦利用WRF模式模擬分析2004年Mmdulle颱風及Tmgting雙颱於季風環流圈中形成之過 程。結果顯示，先（後）形成之Mmdulle颱風(Tmgting)颱風之初始擾動受季風環流圈南側強風軸風切帶 (東側合流區）之綜觀環境強迫條件影響而形成。後因擾動低層環流之建立，外在環境之影響漸漸遠離 擾動中心。結果亦顯示，季風環流圈西側（東側）之Mmdulle (Tmgting)初始擾動發展為熱帶氣旋之關鍵 在擾動中心西北側（東南側）之對流爆發，此對流爆發將導致颱風切向風風場之建立及垂直延伸。本研 究亦模擬分析2006年10月季風環流圈中形成雙颱（Bebmca颱風及Rumbia颱風）之過程，並獲得相似 之分析結果。

The tropical cyclones (TCs) formation in monsoon gyres is examined based on NCEP-FNL grid data and infrared satellite observation. From 2000 to 2009, 10 TCs of 290 (3.4%) western North Pacific TCs are formed in six monsoon gyres, which have to be larger than 2500 km in horizontal scale. Each of the six monsoon gyres embedded two tropical disturbances that would develop to TCs at the west and the east side within the monsoon gyre with a 48-hr delay if no unfavorable factors for TC formation was present. Furthermore, eight of the 10 TCs were embedded in monsoon gyres within where two TCs formed, while the other two TCs were embedded in monsoon gyres with single TC formation. Results also show that TCs formed in monsoon gyres tended to have large sizes. The earlier formation of Typhoon Mindulle (2004) and the later formation of Typhoon Tingting (2004) within the same monsoon gyre are examined with Weather Research and Forecasting Model simulation. Results show that the TC precursor of Mindulle (Tingting) forms under the synoptic-scale forcing of a region with strong horizontal wind shear (confluence region) at the center (eastern part) of the monsoon gyre. After the establishments of TC low-level circulation, convection associated with the synoptic-scale forcing described above occurs away from the centers of the low-level circulation. Results also show that the critical process for Mindulle (Tingting) formation is the convective burst at the northwest (southeast) side of the low-level circulation center, which results to the development and vertical extend of the tangential wind of the TC, after the synoptic-scale-forcing convection is away.