| 摘要: | 台灣氣候受東亞季風環流系統影響至深，由前人研究可知：東亞夏季期間季風系統經歷肇始、活躍、中斷、復甦、消退等各不同階段的環流及降水特徵，致使台灣夏季降水呈雙峰現象；冬季季風期間主要受到由西伯利亞乾冷氣團南下所引發的寒潮現象，並影響熱帶與中緯度地區交互作用。由於福爾摩沙衛星三號星系利用掩星觀測法，能即時觀測全球大氣溫度與溼度剖面資料，並不受海陸分布的限制，而比傳統地面探空觀測提供了更均勻、更豐富的大氣資訊。因此本篇論文利用福衛三號掩星資料，分別針對東亞夏季季風活躍期以及冬季季風寒潮進行研究分析。 在夏季季風活躍期間，福衛三號掩星資料與NCEP分析資料(NCEPana)的全球可降水氣候場，透過其他的衛星水氣氣象參數觀測資料驗證發現，福衛三號掩星資料在熱帶洋面上的水氣觀測比NCEP分析資料更接近實際天氣現象。比較福衛三號掩星資料與NCEP分析資料在短期豪雨天氣現象的描繪，福衛三號掩星資料比NCEP分析資料在積雲降雨區域可以呈現更多的水氣通量輻合，並顯示較合理的水氣變化趨勢。 為更進一步了解春末夏初豪雨現象可能的成因，利用NCEP/GFS高解析度分析資料探討2007年6月3日至2007年6月9日與2007年6月10日至2007年6月16日兩週內不同降水機制的豪大雨現象。結果發現從中國華南地區由西向東移行雨暴受降水潛熱的回饋作用再發展，以及在台灣海峽造成中層大氣渦旋與低層水氣輻合的偶合現象，對雨暴侵襲台灣時的降雨量扮演重要的影響角色。 在冬季利用合成寒潮生命期間，福衛三號掩星資料比NCEP再分析資料(NCEPrii)可以展現較細緻的天氣結構分佈，特別在寒潮乾冷質量流的特徵以及受到其推擠而累積的水氣。福衛三號掩星資料與NCEP再分析資料在寒潮事件降水現象的呈現，福衛三號掩星資料比NCEP再分析資料在鋒面降雨區域較會描繪更多的水氣通量輻散。 The weather and climate in Taiwan are regulated by East Asian monsoon systems including both summer and winter monsoons. Due to the modulation of intraseasonal oscillation, the seasonal marching of the East Asian summer monsoon posses a clear onset, active, break, revival and withdrawal life cycle. Meanwhile, the cold surge originated from Siberia with cold and dry air mass will penetrate Taiwan during the winter. Furthermore, cold surge also will induce a strong midlatitude – tropical interaction. After launching in April 2006, FORMOSAT-3 could provide relative abundant temperature and moisture atmospheric profile by using radio occulation method (RO). The most advantage with this FORMOSAT-3 RO data is not only offering a better global coverage but also providing more vertical observation in the ocean that was scarcely obtained by traditional radiosonde observation. Therefore, it makes possible for us to apply this observational RO data in the East Asian monsoon study, particularly for the summer active monsoon phase and winter cold surge phenomena. During active summer monsoon period, FORMOSAT-3 GPS RO observation depicts a more reasonable atmospheric feature in the tropical cooler ocean area if compared to the NCEP analysis data. Through the water budget analysis, the GPS RO data also demonstrates a better water supply in the hydrological process of the summer rainstorm events. Particularly around the heavy rainfall area with strong convergence of moisture flux, the GPS RO observation shows more agreement than that of NCEP analysis data. Two heavy rainfall events occur during early summer: June 3-9 and June 10-16, 2007. In order to further investigate the possible maintenance mechanisms of these two rainstorms, the high resolution NCEP/GFS analysis data was adopted to perform the detail analysis. It shows that the rainstorm, formed at the southern China, propagates eastward toward Taiwan. During its redeveloping stage, the latent heat release by precipitation together with the coupling of lower boundary moisture convergence and mid-tropospheric vorticity will play significant roles in generating heavy shower resulting in floods in Taiwan. For the winter cold surge events, a cases-composite strategy was used to depict the surge daily development during its life cycle. It appears that the GPS RO observations delineate the surge structure both horizontally and vertically much better than NCEP reanalysis II data, especially the cold dry air mass and water vapor transport. In addition, the GPS RO exhibits a relative stronger divergence of moisture flux in the cold surge rainfall events. |
