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Quasi-vertical profiles (QVPs) obtained from a database of U.S. WSR-88D data are used to document polarimetric characteristics of the melting layer (ML) in cold-season storms with high vertical resolution and accuracy. A polarimetric technique to define the top and bottom of the ML is first introduced. Using the QVPs, statistical relationships are developed to gain insight into the evolution of microphysical processes above, within, and below the ML, leading to a statistical polarimetric model of the ML that reveals characteristics that reflectivity data alone are not able to provide, particularly in regions of weak reflectivity factor at horizontal polarization Z_H. QVP ML statistics are examined for two regimes in the ML data: Z_H≥ 20 dB Z and Z_H< 20 dB Z. Regions of Z_H≥ 20 dB Z indicate locations of MLs collocated with enhanced differential reflectivity Z_DRand reduced copolar correlation coefficient ρ_hv, while for Z_H< 20 dB Z a well-defined ML is difficult to discern using Z_Halone. Evidence of large Z_DRup to 4 dB, backscatter differential phase δ up to 8°, and low ρ_hvdown to 0.80 associated with lower Z_H(from −10 to 20 dB Z) in the ML is observed when pristine, nonaggregated ice falls through it. Positive correlation is documented between maximum specific differential phase K_DPand maximum Z_Hin the ML; these are the first QVP observations of K_DPin MLs documented at S band. Negative correlation occurs between minimum ρ_hvin the ML and ML depth and between minimum ρ_hvin the ML and the corresponding enhancement of Z_H(Δ Z_H= Z_Hmax− Z_Hrain).