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

这项研究集中在使用科罗拉多州立大学的CHILL研究雷达来研究降水雷达回波的偏振特性。一个目标是比较从两种工作模式获得的极化信息：(1)在水平和垂直极化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确定这些模式中的哪一种更适合于诸如估计降雨率的应用。另一个目标是评估和改进一种基于模糊逻辑的降水类型分类方法(雨、冰雹、雪、融化雪等)。通过适当的偏振参数组合。该方法将通过一架穿透风暴的研究飞机(南达科他州地雷和技术学院装甲T-28)进行现场观察来评估。还将研究如何从极化观测中估计雨滴大小分布，使用机载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运行的天气监测雷达网络中引入极化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.