有鑑於降水粒子對於電磁波在大氣中的傳播造成衰減，因此研究降水粒子的特性就相當重要，特別是降水粒子在空中之粒徑分佈的研究。為了探究雨滴粒徑分佈隨高度之變化以及空中降水粒子終端速度與回波功率之關係，在此利用中壢52MHz特高頻雷達以及地面二維影像雨滴譜儀(Disdrometer)，分別得到空中降水粒子之終端速度、回波功率以及地面之降雨率、伽瑪雨滴粒徑分佈。
本次觀測的降水事件為2007年3月24日22:12 LST至24:00 LST鋒面系統所造成之降水，由觀測之經驗式或由理論推導皆可得知，伽瑪雨滴粒徑分佈的兩個參數斜率Λ和形狀μ之間的關係可用二次多項式來描述，假設空中之雨滴粒徑分佈也滿足此一特性，利用雷達所得到的空中降水粒子的終端速度及回波功率，可得到空中降水粒子之伽瑪雨滴粒徑分佈。並且利用雨滴譜儀所得之資料，深入探討伽瑪雨滴粒徑分佈參數與降水參數間之關係。最後，空中降水粒子的終端速度和回波功率之間的關係，可由指數型態之雨滴粒徑分佈及伽瑪雨滴粒徑分佈兩種不同的雨滴粒徑分佈模型，分別得到不同的結果。

Because the precipitation particles will attenuate electromagnetic wave propagating in the atmosphere, the study of their characteristic is very important, especially for DSD (Drop Size Distribution) in the air. To investigate the variation of the DSD with the height and the relation between the precipitation terminal velocity and the backscattering echo power of raindrop, the precipitation terminal velocity, the backscattering echo power of raindrop in the air and the rain fall rate, gamma DSD in the ground separately from the Chung-Li 52MHz VHF radar and the 2-D video disdrometer are employed.
The data used in this study were taken on March 24, 2007, from 22:12 to 24:00 LT by Chung-Li VHF radar, and the weather type is frontal area system. It is found that the relation between the slope and shape parameters of the gamma DSD can be described by a polynomial of second degree empirically and theoretically. If this characteristic is also satisfied with the gamma DSD in the air, we can obtain the gamma DSD in the air using the precipitation terminal velocity and the backscattering echo power of raindrop from the radar. Using the data obtained by disdrometer, we can investigate the relation between the parameters of the gamma DSD and the parameters of precipitation thoroughly. Finally, there are different results by using the exponential form DSD and the gamma form DSD in the relation between the precipitation terminal velocity and the backscattering echo power of raindrop.

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