Polarimetric Radar Observations of Precipitation: Measurements, Analysis, Modeling and Retrievals

本研究以科罗拉多州立大学的CHILL研究雷达为中心，研究降水雷达回波的偏振特性。 一个目的是比较可从两种操作模式获得的偏振信息：（1）在水平和垂直偏振之间快速切换发射波形;（2）发射圆偏振并同时接收水平和垂直分量-所谓的混合模式。 实验将确定这些模式中哪一种更适合于应用，例如通过将雷达反射率的测量与描述雷达信号的偏振特性的各种参数相结合来估计降雨率。 另一个目标是评估和改进一种基于模糊逻辑的降水类型（雨、冰雹、雪、融雪等）分类方法。通过极化参数的适当组合。 该方法将通过一架穿透风暴的研究飞机（南达科他州矿业与技术学院装甲T-28）进行现场观测来评估。 还将调查的方法来估计雨滴大小分布的偏振观测，使用空中和地面测量进行验证。 这些研究将为目前正在进行的在国家气象局操作的天气监视雷达网络中引入偏振测量的规划提供重要指导。

This research centers on using the CHILL research radar at Colorado State University to study the polarization properties of radar echoes from precipitation. One objective is to compare the polarimetric information available from two modes of operation: (1) rapidly switching the transmitted wave form between horizontal and vertical polarization; (2) transmitting circular polarization and simultaneously receiving the horizontal and vertical components - the so-called hybrid mode. Experiments will determine which of these modes is more suitable for applications such as estimating rainfall rate by combining measurements of the radar reflectivity with various parameters that describe the polarimetric properties of the radar signal. Another objective is to evaluate and refine a method based on fuzzy logic of classifying the type of precipitation (rain, hail, snow, melting snow, etc.) by a suitable combination of polarimetric parameters. The method will be evaluated by in-situ observations by a storm-penetrating research aircraft (the South Dakota School of Mines and Technology armored T-28). Also to be investigated are ways to estimate the raindrop size distribution from polarimetric observations, using both airborne and ground-based measurements for verification. These studies will provide important guidance for the planning, now under way, to introduce polarimetric measurements in the network of weather surveillance radars operated by the National Weather Service.