MODELING MELTING LAYER RADAR OBSERVATIONS AT GPM FREQUENCIES; COMPARISON TO MEASUREMENTS

The melting layer attenuation is studied by fitting the modeled reflectivity factor and the reflectivity-weighted fall velocity to measured values at both Ku- and Ka-bands. In the fitting process the optimized snow density and velocity parameters are defined and the dependence of the modeled attenuation on these parameters is investigated. The study shows that for Ku-band the implemented model can describe the melting layer with sufficient accuracy, but for Ka-band there is discrepancy between the measured and modeled values despite the fitting process. At Ka-band the attenuation of water vapor and cloud water influence more than at Ku-band and this should be considered also in the model. The sensitivity study of the modeled attenuation shows that in the snow velocity power-law function V = alpha D-beta the changes in the factor alpha induces a significant deviation in the modeled attenuation. This is true for all of the tested effective permittivity models and at both frequency bands. The permittivity model of a coated sphere solution is out of the tested models the most susceptible on changes of snow related parameters.