由於雨滴粒徑分布可以決定雲中液態水含量(W)、雷達的回波強度(Z)以及降雨率(R) 等降雨積分參數，雨滴粒徑分布不但是雷達降雨估計技術的關鍵資料。而且也是描述降雨物理的一個基本量，因此分析雨滴粒徑分布與變化之特性是定量降水估計(QPE)非常重要的研究工作。本研究將以TIMREX/SOEMEX 實驗期間佈置在台灣西南部地區的四部撞擊式雨滴譜儀以及一部光學式的二維視訊雨滴譜長期觀測資料，搭配雷達，特別是 NCAR S-pol 與移動式X-band 之TEAM 雙偏極化雷達與垂直剖風儀雷達的觀測來統計分析台灣地區梅雨季節不同降水型態下的雨滴粒徑分布與變化特性。統計分析各種降雨參數之間的關係，特別是降雨率與回波，降雨率與雨滴粒徑分布關係之變化特性。另外本研究計畫擬藉由雨滴譜的觀測，配合雙偏極化都卜勒雷達資料，區分層狀與對流降雨之結構，解析降水凝結物之下降速度以及雨滴粒徑分布，並以定點地面雨滴譜儀結合UHF 雷達對雨滴粒徑分布的觀測計算之降水參數R、Z，作為雷達觀測資料之 Z-R 關係的驗證，以期建立雷達雨量估計Z-R 關係式，計算gamma-fitted parameter，尋求參數分布型態與雨雲間之關聯性，以改進梅雨期之定量降水估計技術，並針對不同降雨型態進行分類探討。由於 S-pol 與TEAM 兩部雙偏極化雷達，均可以提供除了回波與徑向速度之外的雙偏極化雷達參數，本計劃將用這些雙偏極化參數來反演降雨率，反演之方法包括先反演雨滴粒徑分布再反推降雨率，和直接使用經驗公式由雙偏極化參數直接反求降雨率並以地面雨量站網進行驗證和比較。 ; Measurements of the drop size distribution (DSD) have a broad range of applications in meteorology, hydrology and related sciences. In particular accurate estimate of a real rainfall through radar measurements. Benefit from the knowledge of the drop size distribution. The use of radar to make quantity precipitation estimate (QPE) requires a relationship between its measured reflectivity Z and the estimated rainfall. Such a relationship, Known as Z-R, can be derived from long term observations of DSD using disdrometers. In this project, the drop size distribution will be observed by a disdrometer network (four impact disdrometers and one 2-D Video disdrometers) during TIMREX/SOWMEX period in south-western Taiwan will be classified and analyzed. The distribution of DSDs in time and space in Mei- yu season will be discussed. The DSD data will be used directly to derive the Z-R relation through the Gamma distribution fit of DSD. The radar reflectivity field will be used to compared to the reflectivity calculated from the observed distribution of DSD will also be discussed in this project. S-pol radar and TEAM dual-polarization radar can be used to retrieve the DSD from the polarimetric variables, it also can provide more correct rainfall estimate than the Doppler weather radar. The main goal of this project is to develop the optimum rainfall algorithm by using the disdrometers and polarimetric radar observation from TIMREX/SOWMEX field campaign. ; 研究期間 9708 ~ 9807
