Rainfall estimation from polarimetric radars: Algorithms immune to variability in mean raindrop shape

The most commonly used polarimetric radar measurements in rainfall estimation are the reflectivity factor, usually at horizontal polarization (Zh), differential reflectivity (Z_dr) and specific differential propagation phase (K_dp). Based on the above three measurements, a number of algorithms have been derived in the literature to estimate rainfall. These algorithms have been derived assuming equilibrium raindrop shapes, described by a shape-size relationship. The mean axis ratio versus size relation is crucial for deriving algorithms that use Z_dr and K_dp. Gorgucci et al. demonstrated that the slope of a linear mean raindrop shape-size relation can be estimated from polarimetric radar measurements. The goal of this paper is to incorporate the results of Gorgucci et al. into rainfall estimation algorithms so that the algorithms can be used for any prevailing mean raindrop shape without any prior assumption of the shape-size model