SEMINAR SERIES and COLLOQUIA

A general polarimetric radar emulator is developed based on rigorous scattering calculations using the T-matrix method for reflectivity, differential reflectivity, specific differential phase, and co-polar cross-correlation coefficient. A continuous melting process accounts for the entire spectrum of varying density and dielectric constants. This emulator is able to simulate polarimetric radar measurements at weather radar frequency bands and can take as input the prognostic variables of high-resolution nonhydrostatic NWP model simulation using one-, two-, and tree-moment microphysics scheme.

The new emulator is tested at 10.7 cm of wavelength with a model-simulated supercell storm using two-moment microphysics schemes (DM) to simulate unique polarimetric signatures reported in the observational studies. Simulated fields exhibit realistic polarimetric signatures that include ZDR and KDP columns; ZDR arc, mid-level ZDR and ρhv rings; and hail signature in terms of the general location, shape and strength. We compared this simulation to one employing a one-moment microphysics scheme and found that certain signatures cannot be produced, such as ZDR arc and mid-level ZDR and ρhv rings, which are associated with the size sorting mechanism. These results suggest that two- or higher-moment microphysics should be used to describe supercell microphysics and kinematics more accurately. They are also a good example of the emulator’s capabilities as a validation tool for numerical models. In addition, the simulator may also serve forecasters by providing them an opportunity to look at and quickly and intuitively interpret the model polarimetric fields in advance.

Back to NWC Seminar Series and Colloquia