Assimilation of Simulated Polarimetric Radar Data for a Convective Storm Using the Ensemble Kalman Filter. Part I: Observation Operators for Reflectivity and Polarimetric Variables
نویسندگان
چکیده
A radar simulator for polarimetric radar variables, including reflectivities at horizontal and vertical polarizations, the differential reflectivity, and the specific differential phase, has been developed. This simulator serves as a test bed for developing and testing forward observation operators of polarimetric radar variables that are needed when directly assimilating these variables into storm-scale numerical weather prediction (NWP) models, using either variational or ensemble-based assimilation methods. The simulator takes as input the results of high-resolution NWP model simulations with ice microphysics and produces simulated polarimetric radar data that may also contain simulated errors. It is developed based on calculations of electromagnetic wave propagation and scattering at the S band of wavelength 10.7 cm in a hydrometeor-containing atmosphere. The T-matrix method is used for the scattering calculation of raindrops and the Rayleigh scattering approximation is applied to snow and hail particles. The polarimetric variables are expressed as functions of the hydrometeor mixing ratios as well as their corresponding drop size distribution parameters and densities. The presence of wet snow and wet hail in the melting layer is accounted for by using a new, relatively simple melting model that defines the water fraction in the melting snow or hail. The effect of varying density due to the melting snow or hail is also included. Vertical cross sections and profiles of the polarimetric variables for a simulated mature multicellular squall-line system and a supercell storm show that polarimetric signatures of the bright band in the stratiform region and those associated with deep convection are well captured by the simulator.
منابع مشابه
Assimilation of Simulated Polarimetric Radar Data for a Convective Storm Using Ensemble Kalman Filter. Part I: Observation Operators for Reflectivity and Polarimetric Variables
i Abstract A radar simulator for polarimetric radar variables including reflectivities at horizontal and vertical polarizations, the differential reflectivity and the specific differential phase, has been developed. This simulator serves as a testbed for developing and testing forward observation operators of polarimetric radar variables that are needed when directly assimilating these variable...
متن کاملAssimilation of Simulated Polarimetric Radar Data for a Convective Storm Using Ensemble Kalman Filter. Part II: Impact of Polarimetric Data on Storm Analysis
i Abstract A data assimilation system based on the ensemble square-root Kalman filter (EnSRF) is extended to include the additional capability of assimilating polarimetric radar variables. It is used to assess the impact of simulating additional polarimetric observations on convective storm analysis in an OSSE (Observing System Simulation Experiment) framework. The polarimetric variables consid...
متن کاملAssimilation of Simulated Polarimetric Radar Data for a Convective Storm Using the Ensemble Kalman Filter. Part II: Impact of Polarimetric Data on Storm Analysis
A data assimilation system based on the ensemble square-root Kalman filter (EnSRF) is extended to include the additional capability of assimilating polarimetric radar variables. It is used to assess the impact of assimilating additional polarimetric observations on convective storm analysis in the Observing System Simulation Experiment (OSSE) framework. The polarimetric variables considered inc...
متن کاملAssimilation of Polarimetric Radar Data Using Ensemble Kalman Filter: Experiment with Simulated Data
Since the use of differential reflectivity for rainfall estimation was first proposed by Seliga and Bringi (1976), many studies have shown that polarimetric measurements can improve precipitation type classification and quantitative precipitation estimate (Straka et al. 2000). Moreover, the polarimetric radar (PR) upgrade plan of the National Weather Services (NWS) for the operational WSR-88D n...
متن کامل