The use of optimal polarizations for studying the microphysics of precipitation: Nonattenuating wavelengths

Abstract The objective of this work is to explore relationships between the microphysical properties of precipitation and optimal polarizations. The dependence of three optimal polarization parameters (asymmetry ratio 𝒜, optimal tilt τop, and optimal ellipticity ϵop,) on the reflectivity-weighted mean drop shape, mean canting angle, and standard deviation of a Gaussian canting angle distribution is studied. This is accomplished by using computer simulations that provide the rms scattering matrix for an ensemble of canted drops with a prescribed two-parameter canting angle distribution. Also examined are the effects of propagation on the polarization parameters for nonattenuating wavelengths. The asymmetry ratio 𝒜 is simply the ratio of the maximal to minimal total backwattered energy (ratio of the largest and smallest eigenvalue of the Graves power matrix G=S†). Similar to ZDR, this ratio decreases with increasing mean axial ratio, but unlike ZDR, it is not affected by canting (for a single drop). The dep...