Progress and Prospects of Advanced Radar Refractivity Retrieval
Radar refractivity is a proxy for two dimensional near-surface moisture fields and can be retrieved within about a 50-km radius of radars. This technique is based on the temporal phase variation from ground targets as an indication of the refractivity change along the radar beam path. Refractivity is most sensitive to moisture variations near the ground. High temporal and spatial resolution refractivity maps have been previously used to study the spatial variation of near-surface moisture associated with convection evolution and boundary layer processes, as well as for assimilation in numerical weather prediction models to improve quantitative precipitation forecasting skills. However, data quality concerns regarding the representativeness of the refractivity maps, simplified assumptions of the retrieval method, and unknown error quantification have limited the applications in recent years. This presentation will introduce recent progress in the development of radar refractivity retrieval algorithms. Three-dimensional refractivity information is provided, consisting of a horizontal map at a given height above the terrain and the averaged refractivity profile over the data coverage. The temporal evolution of the refractivity profile captures the diurnal mixing conditions within the lowest levels of the atmosphere. The observational bias and error of the retrieved refractivity fields are quantified based on an improved understanding of the fundamental characteristics of ground targets and the uncertainties of the phase measurements as well as the retrieval. The knowledge of the error of the retrieved product is essential both for data assimilation and future technique improvements. The operational WSR-88D radar network may someday implement the advanced refractivity retrieval technique. This could advance the understanding of the moisture distribution associated with heterogeneous land surfaces, such as urban-rural contrast, and it might help improve the initialization of near-surface thermodynamic conditions for models at various resolutions.
Semiar will be webcast at: http://www.fin.ucar.edu/it/mms/fl-live.htm
Tuesday 02, May, 2017 3:30 PM
NCAR Foothills Laboratory
3450 Mitchell Lane
Bldg 2 Large Auditorium (RM1022)