Multi-Frequency Radar and Microwave Radiometer Simulations of Surface Snowfall Events from GCPEx: Synergistic Application of In-Situ Microphysics Observations with Modeled Ice Scattering Properties

Preliminary results from a combined radar-microwave radiometer study using in-situ microphysics data and other observations from the Global Precipitation Measurement (GPM) Cold season Precipitation Experiment (GCPEx) will be presented in this study. The primary purpose of this work is to assess microwave ice particle scattering models by comparing forward model calculations with dual-frequency airborne radar and multi-frequency passive microwave observations of select surface snowfall events from GCPEx. Forward model radar and radiometer calculations require snowflake scattering properties to be integrated over particle size distributions, and both of these inherent microphysical quantities strongly influence unconstrained radar-radiometer simulations under snowing conditions. Therefore, direct airborne and ground-based ice particle size distribution measurements and other relevant microphysical properties will be used to build a physically realistic microphysical rendition of the atmospheric column to simulate both layer radar reflectivity signatures and top-of-the-atmosphere microwave radiometer brightness temperatures for select GCPEx cases. Comparisons of measured particle size distributions will also be made to particle size distribution parameter retrievals from airborne-only observations, and the subsequent sensitivity in simulated brightness temperatures will be discussed. Other simulation complicating factors (e.g., surface emissivity effects, cloud liquid water location and amount, etc.) and implications for GPM radar and radiometer retrievals will also be highlighted.