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.
