對於迦碼雨滴粒徑分布(Gamma Rain Drop Size Distribution) N(D)=N0Dexp(-D)而言，斜率參數(Slope Parameter)以及形狀參數(Shape Parameter)決定了雨滴粒徑分布的特性，包括眾數(Mode)、平均值(Mean)、中間值(Median)、偏態(Skewness)與陡度(Kurtosis)等。在對流性降雨(Convective Precipitation)的發展與形成的過程中，由於需要大氣垂直運動提供水汽以及凝結核和營造適當的熱力環境以利降雨的發生，因此往往伴隨有大氣垂直運動的存在。然而在目前現有的剖風雷達降雨回波訊號反演空中降雨粒徑分布的方法中，並未考慮大氣垂直運動因素，以致影響剖風儀反演出的空中雨滴粒徑分布的正確性。在本計畫中，將根據剖風儀降雨回波參數化(Echo Parameterization)的理論，發展剖風雷達反演空中降雨粒徑分布的回波分析處理方法，並利用中壢特高頻雷達所觀測到降雨回波以及大氣折射指數回波，研究並了解大氣垂直速度透過大氣拖曳力(Air Drag)對於剖風雷達反演空中雨滴粒徑分布參數，亦即斜率參數以及形狀參數，的影響程度。 ;For Gamma rain drop size distribution N(D)=N0Dexp(-D), the slope parameter and shape parameter govern the characteristics of the Gamma DSD, including model, mean, median, skewness and kurtosis, and so on. The vertical air motion not only can provides water vapor and condensation nuclei, but also paves a suitable precipitation environment for the development and formation of the rain drops for the convective precipitation. As a result, the precipitation event will usually accompany the vertical air motion. However, in the existing algorithms of estimating the rain drop size distribution from windprofiler-observed precipitation echoes, the effect of the vertical air motion on the drop size distribution did not be considered, leading to the retrieved drop size distributions are in question. In this proposal, on the basis of the theory of the echo parameterization for a wind profiler, an algorithm that can be employed to retrieve the drop size distribution aloft will be developed to study the effect of the vertical air motion on the drop size distribution deduced from the wind profiler-observed precipitation echoes. We hope that this study can give us a clear picture of how the drop size distribution aloft will be changed with the vertical air motion through the air drag exerting on the droplets of the drop size distribution.
