Simulated Frequency Dependence of Radar Observations of Tornadoes

Frequency dependence of equivalent reflectivity factor and Doppler velocity in tornadoes is examined using two different electromagnetic scattering calculation techniques, T-matrix and Physical Optics Approximations. To provide realistic particle motion in tornadoes, debris and rain drop trajectories are computed using a Large-Eddy Simulation (LES) model. Radar variables are then simulated using LES particle concentrations and velocities, and electromagnetic scattering calculations.

Radar variable simulations reveal significant frequency dependence of both equivalent reflectivity factor and Doppler velocity in tornadoes. Error analyses of debris centrifuging effects on Doppler velocity and single-Doppler three-dimensional wind retrievals are performed for common weather radar frequencies, including comparisons between the two electromagnetic scattering calculation techniques. The potential of dual-wavelength radar observations to quantify differences between air and Doppler velocities, and to estimate particle size, is explored. Finally, a dual-wavelength technique to compute Rayleigh and Mie scattering contributions to equivalent reflectivity factor at cm-wavelengths is discussed.