本研究使用的資料來源為中央大學Joss-Waldvogel disdrometer(JWD)觀測資料與中央氣象局(CWB)三維雷達回波合成資料(QPESUMS)，統計的區間為2005年1月至2014年12月間。由標準化的gamma分布顯示,平均直徑Dm (Mass-weighted average diameter)於夏季有最高值，而平均Nw(normalized intercept parameter)最高值則出現在冬季; 透過雷達回波在高度上的變化得知垂直發展影響DSD (drop size distribution)在不同季節的結果。此外，台灣北部降雨率多集中於20mm/hr以下(層狀性降水)，本篇研究使用雷達回波區分對流性與層狀性降雨，移除層狀性降水主導的因素。所有季節的層狀降雨皆有相近的DSD分布結構，但對流降雨的DSD則是偏向海洋型對流; 平均Dm在對流降雨系統有較高值，而平均log10Nw在層狀系統內有較高值，透過 Contoured frequency by altitude diagrams (CFADs)發現垂直發展主導DSD的變異性。
;Drop size distribution (DSD) is a metric widely used in meteorology and hydrology. Taiwan is located in a subtropical monsoon area in the west Pacific Ocean off the coast of East Asia. Enormous quantities of rainfall during the transition season often cause flooding and mudslides. Accurate rainfall prediction can help to alleviate the effects of such rainfall events. DSD varies with regard to the type of rain as well as its spatial distribution. Radar reflectivity-rate of rainfall (Z-R) relations are strongly dependent on DSD variations, which means that it is important to analyze the DSD in various seasons as well as in various types of rain.
Between January 2005 and December 2014, DSD data was collected using a Joss-Waldvogel Disdrometer (JWD) to analyze variations in the Gamma parameters of raindrop spectra at NCU (24°58′6"N 121°11′27"E). The normalized Gamma distribution of DSD revealed that the highest mean Dm (Mass-Weighted Average Diameter) values were in summer, whereas the highest mean log10Nw (normalized intercept parameter) values were in winter. Vertical structures detected in radar reflectivity profiles dominate the results of seasonal DSD. Furthermore, most of the rain falling at less than 20 mm/hr (stratiform precipitation) occurs in Northern Taiwan. In this study, we used radar reflectivity to differentiate between convective and stratiform systems. It was discovered that the mean Dm value is higher in convective systems, whereas the mean log10Nw value is higher in stratiform systems. The structure of DSD in stratiform systems remains constant in all seasons; however, convection is similar to maritime type. Contoured Frequency by Altitude Diagrams (CFADs) revealed that vertical structures dominate DSD in various types of precipitation.
