Vertical Profile Climatology of Polarimetric Radar Variables and Retrieved Microphysical Parameters in Synoptic and Lake Effect Snowstorms.

This study derives polarimetric radar vertical profiles and microphysical retrievals for 25 Synoptic Snow (SS) and 23 Lake Effect Snow (LES) cases using the Range‐Defined Quasi‐Vertical Profiles (RD‐QVP), Columnar Vertical Profiles (CVP), and Process‐oriented Vertical Profiles (POVP) methods. For all vertical profile techniques, SS cases exhibit a near‐linear increase in reflectivity from −30 to 0°C whereas ZDR and Kdp locally peak in the dendritic growth layer. LES cases universally exhibit negative ZDR, rather high Z, negligible Kdp, and near‐unity ρhv. Ground measurements from the past OWLeS campaign provide direct evidence that conical graupel may strongly affect these polarimetric measurements in LES bands. Aggregation efficiencies for SS cases are estimated by optimizing the theoretical number concentration (Nt) and mean volume diameter (Dm) steady‐state vertical profiles against radar‐retrieved profiles derived from 20 of the 25 synoptic storm RD‐QVPs. The median estimated aggregation efficiency is approximately 0.15 with a relatively narrow interquartile range that spans from 0.1 to just over 0.2. Values of optimized aggregation efficiencies are nearly independent of the assumed gamma distribution shape parameter. These results are used to derive temperature‐dependent, climatological steady‐state relations for vertical profiles of Nt, Dm, and liquid‐equivalent snowfall rates. These results can be used in numerical weather prediction model aggregation parameterizations and can also provide climatologically representative vertical profiles of radar and microphysical quantities. Plain Language Summary: This study documents the climatology of the vertical profiles of polarimetric radar variables and microphysical parameters in synoptic snow (SS) and lake effect snow (LES) using polarimetric radars in the U.S. The SS vertical profiles show a generally enhanced signal from cloud top to the surface and a noticeable dendritic growth layer signature near −15°C. As for LES vertical profiles, we noticed a negative ZDR pattern with strong Z and weak KDP signals. Further investigation reveals the existence of conical graupel that caused negative ZDR near ground level. This study also summarizes estimated aggregation efficiencies for the SS cases. It shows that the aggregation efficiencies are nearly independent of the commonly used gamma distribution shape parameter. Equations are derived for representing parameters and vertical profiles resulting from aggregation. The overall work from this study provides climatologically representative vertical profiles of radar and microphysical quantities, and can be used as a reference for model parameterization improvement. Key Points: Climatological vertical profiles of synoptic snow and lake effect snow are summarized using polarimetric radarsLake effect snow exhibits negative values of ZDR which are caused by conical graupelSynoptic snow aggregation efficiencies are estimated by combining radar climatology with theoretical relations [ABSTRACT FROM AUTHOR]