Impact of Mass-Size Parameterizations of Frozen Hydrometeors on Microphysical Retrievals: Evaluation by Matching Radar to In Situ Observations from GCPEx and OLYMPEx

This article illustrates how multi-frequency radar observations can refine themass-size parametrization of frozen hydrometeors in scattering models andimprove the correlation between the radar observations and in situ measurementsof microphysical properties of ice and snow. The data presented in thisarticle were collected during the GCPEx (2012) and OLYMPEx (2015) fieldcampaigns, where the true mass-size relationship was not measured. Startingfrom size and shape distributions of ice particles measured in situ, scatteringmodels are used to simulate an ensemble of reflectivity factors for variousassumed mass-size parameterizations (MSP) of the power-law type. This ensembleis then co-located to airborne and ground-based radar observations,and the MSPs are refined by retaining only those that reproduce the radar observationsto a prescribed level of accuracy. A versatile “retrieval dashboard”is built to jointly analyze the optimal MSPs and associated retrievals. Theanalysis shows that optimality of an MSP depends on the physical assumptionsmade in the scattering simulators. This work confirms also the existenceof a relationship between parameters of the optimal MSPs. Throughthe MSP optimization, the retrievals of ice-water-content M and mean diameterDm seem robust to the change in meteorological regime (between GCPExand OLYMPEx); whereas the retrieval of the diameter spread Sm seems morecampaign-dependent.