Emulation of Polarimetric Weather Radar Signals from Tornadic Debris

A numerical emulator provides us opportunities to understand a complex process by breaking down contributions from each variable one at a time under a fully controllable environment. In an effort to try to understand various scattering characteristics of debris in tornadoes, which promises insights into their radar signatures, a numerical polarimetric radar time-series emulator has been developed. The emulator generates radar time-series data by coherently integrating signals from scattering bodies in a finite volume, analogous to the Monte Carlo method. The scattering bodies are comprised of two constituents: one represents the atmospheric background while the other represents debris lofted by a tornado vortex. The atmospheric background is driven by wind field generated using a Large Eddy Simulation (LES) model, which has been previously developed in a separate study. The LES model provides various types of vortex configurations, i.e., vortex breakdown or suction vortices. The wind field is used to drive the motions of the scattering bodies to emulate atmospheric motions. For the debris, each piece is represented by a scattering body, which has its own unique radar cross section (RCS) characteristics at different orientations, depending on the incident angle and polarization of the radar electromagnetic wave. Depending on the object, the RCS is determined through analytical calculations, libraries generated by high-fidelity simulations, and anechoic chamber measurements of actual debris. Some preliminary results of simulations and comparison to actual radar data are presented.