Winter Precipitation Microphysics with Polarimetric Radar and Explicit Modeling

通过各种研究雷达和业务(例如，由美国国家海洋和大气层管理局升级后的WSR-88D网络提供)提供的更常规的双极化雷达测量的出现，为交叉比较这些观测和相关的建模提供了一个重要的新机会，特别是在涉及尚未彻底研究的冻结或混合降水的冷季环境中。这项工作的目标是记录和解释冬季风暴中的双极化雷达信号，并量化各种冬季微物理过程对观测到的极化雷达变量模式的影响。这些目标将通过综合极化雷达观测和热力学数据、二维视频碟形仪测量、电磁散射计算和光谱(Bin)微物理模型的输出来实现。S用工作在S、C和X波段的偏振雷达同时扫描的几组独特的冬季降水事件的数据集已经显示出新的特征，具有很大的科学和实用前景。这些特征中的一个迄今没有记录在案，但在几个冬季风暴案例中重复出现，涉及发展出明显是由于融化或部分融化的水流星体重新冻结成冰球而产生或与之相关的冰晶形成的“二次”亮带特征。此外，未来的冬季风暴将使用俄克拉荷马州诺曼(Koun)的极化原型WSR-88D雷达、新安装的俄克拉荷马大学气象与工程创新窄波束极化雷达(OU-Prime)以及由NOAA国家严重风暴实验室和俄克拉荷马大学共享的移动X波段极化雷达(NOXP)来观测。这项研究将涉及两个主要目标。首先，将把工作在不同波长的多个雷达对冬季风暴的极化观测与来自测深和数值天气模式分析的热力学数据结合起来，以描述和解释观测到的极化特征，并将记录重复特征，以形成更完整的冬季风暴极化图像。其次，将建立一维和二维的显式“面元”和整体微物理模式，以探索和量化微物理过程在冬季降水中的作用，如沉积生长、聚集、结圈、融化和再冻结，并反过来更好地确定其通过雷达观测变量的表示。这些面元模型将通过将模型输出与电磁散射计算配对，努力定量地再现观测到的冬季风暴结构。这一努力的智力价值将在于更好地理解树枝状生长、颗粒边缘和高空聚集的作用，包括表面附近的熔化和重新冻结过程，这将有助于改进数值模型中使用的整体微物理参数化。反过来，这将导致更好的定量降水预报和冬季天气灾害预报。改进对冬季云和降水物理(包括融化层)的地面遥感的解释，可能有助于NASA卫星降水估计和气候研究。此外，更好地了解冬季风暴中的偏振雷达测量可能会导致改进冬季天气的水流星分类算法。更广泛的影响将包括改进对冬季降水类型对比的诊断和区分，以及通过地面和卫星遥感技术对其进行诊断。这些进展反过来将对地面和航空运输界产生相当大的价值，从而有助于改善公共安全。

The advent of more routinely available dual-polarization radar measurements available both via a variety of research radars and operationally (e.g., to be provided by NOAA's upgraded WSR-88D network) offers an important emerging opportunity for cross-comparison of these observations and associated modeling, especially in cool-season environments involving frozen or mixed precipitation that have not been thoroughly studied. The goals of this effort are to document and interpret dual-polarization radar signatures in winter storms and to quantify the impact of various winter microphysical processes on observed patterns of polarimetric radar variables. These goals will be attained by synthesizing polarimetric radar observations and thermodynamic data, 2-D video disdrometer measurements, electromagnetic scattering calculations, and output from spectral (bin) microphysics models. S everal unique datasets of winter precipitation events scanned contemporaneously with polarimetric radars operating at S-, C- and X-band wavelengths have already been collected that reveal new signatures which hold great scientific and practical promise. One of these signatures, heretofore undocumented but repeated in several winter storm cases, involves development of a "secondary" bright-band signature that is apparently caused by ice crystals generated or associated with the refreezing of melted or partially-melted hydrometeors into ice pellets. Additionally, future winter storms will be observed using the polarimetric prototype WSR-88D radar in Norman, Oklahoma (KOUN), the newly-installed narrow beam University of Oklahoma Polarimetric Radar for Innovations in Meteorology and Engineering (OU-PRIME), and a mobile X-band polarimetric radar (NOXP) shared by NOAA's National Severe Storms Laboratory and the University of Oklahoma. Two major objectives will be addressed in the study. First, polarimetric observations of winter storms from multiple radars operating at diverse wavelengths will be combined with thermodynamic data from soundings and numerical weather model analyses to describe and interpret observed polarimetric signatures, and repetitive signatures will be documented to develop a more complete polarimetric portrait of winter storms. Second, one- and two-dimensional explicit "bin" and bulk microphysics models will be constructed to explore and quantify the role of microphysical processes such as depositional growth, aggregation, riming, melting, and refreezing in winter precipitation, and in-turn to better determine their representation by radar-observed variables. These bin models will be applied in an effort to quantitatively reproduce observed winter storm structure by pairing model output with electromagnetic scattering calculations. The Intellectual Merit of this effort will rest in improved understanding of the roles of dendritic growth, particle riming and aggregation aloft, processes including melting and re-freezing near the surface, which will contribute to improved bulk microphysics parameterizations used in numerical models. In turn, this will lead to better quantitative precipitation forecasts and forecasts of winter weather hazards. Improved interpretation of ground-based remote sensing of winter clouds and precipitation physics, including the melting layer, may help NASA satellite precipitation estimation and climate studies. Additionally, a better understanding of polarimetric radar measurements in winter storms may lead to an improved hydrometeor classification algorithm for winter weather. Broader impacts will include improved diagnosis and discrimination of contrasting winter precipitation types and their diagnosis via both ground-based and satellite-borne remote sensing techniques. These advances will in-turn have considerable value to the surface and aviation transportation communities, and thus contribute toward improved public safety.