Simulations of Spectral Polarimetric Variables measured in rain at W-band

Abstract. In this work, the T-matrix approach is exploited to produce simulations of spectral polarimetric variables (spectral differential reflectivity, sZ_DR, spectral differential scattering phase, sδ_HV and spectral differential correlation coefficient, sρ_HV) for observations of rain acquired from a slant-looking W-band cloud radar. The spectral polarimetric variables are simulated with two different methodologies, taking into account the instrument noise and the stochastic movement of the raindrops introduced by raindrop oscillations and by turbulence. The simulated results are then compared with rain Doppler spectra observations from a W band millimeter-wavelength radar for moderate rain rate conditions. Two cases, differing in levels of turbulence, are considered. While the comparison of the simulations to the measurements presents a reasonable agreement for equi-volume diameters less than 2.25 mm, large discrepancies are found in the amplitude (but not the position) of the maxima and minima of sZ_DR and, more mildly, of sδ_HV. This pinpoints at a general weakness of the raindrops approximation with spheroids for simulating radar backscattering properties at W-band.