台灣地區劇烈天氣可大致分為颱風季節的強風和豪雨、梅雨季節的豪雨、鋒面附近中尺度對流系統以及伴隨雷雨的冰雹、閃電等。氣象雷達是偵測以及即時預報此類劇烈天氣最重要的工具，本計畫將以先進的雷達資料，包括偏極化雷達參數及都卜勒雷達參數，發展劇烈天氣預報技術。偏極化雷達可以觀測雨滴的粒徑分布、形狀及降水粒子的分類，採用偏極化雷達參數可以求出正確的降雨率、降雨公式，並且可以校驗氣象局網連的回波降雨公式。而本計畫今年最重要的部分，即為將中央大學都卜勒雷達系統進一步升級為偏極化/都卜勒雷達。結合雨滴譜儀和雙偏極化雷達的觀測，可以大幅改善這方面的問題，因此本計畫主要的目標之一就是將發展偏極化雷達硬體技術及軟體分析能力，從基本學理上改進中央氣象局目前雷達網連所使用的降水估計技術，建立雷達觀測資料的資料校驗系統，並做為未來氣象局全面發展偏極化雷達之前驅研究計畫。 Since 2002, the radar network of Central Weather Bureau has started its full operation. The major purpose of this project is to utilize the radar data to develop the useful algorithms and techniques for short range forecasting on severe weather, such as heavy rain during Typhoon and Mei-Yu, severe thunderstorms, etc. The rainfall estimate products from the radar observation have also been provided to forecast center of Bureau and other agencies such as the Water Resources Agency and Disaster Mitigation Center. However, because of the different rain drop distribution characteristics of each rainfall event, the variation of the relations between radar reflectivity and the rainfall rate estimation (Z-R relation) is quite large. So the single formula for the Z-R relation often underestimates the rainfall during heavy rain. The complex terrain also cause ground clutter and the blocking of radar beam energy, these factors also induce rainfall estimate errors. In the first year of this project, our work will be focused on the Polarization upgrade of the NCU Doppler radar. The polarimetric variables observed by this new kind radar can provide drop size distribution, drop oblateness, and hydrometer types in a precipitation system. The real time drop size distribution can be used to calibrate the conventional weather radar at Wufansen. Because of the importance of polarimetric radar to the severe weather forecasting, this project will also be the risk reduction project for the future possible development of Central Weather Bureau radar application. 研究期間：9302 ~ 9312
