Profiling Radar and Snow Microphysical Properties from Extended Ground Observations in the Upper Great Lakes

This study presents results from a ground-based profiling radar and in-situ snow microphysics observational suite located at the Marquette, Michigan National Weather Service Weather Forecast Office in the Upper Great Lakes near the southern shore of Lake Superior. Combined Micro Rain Radar (MRR) and Precipitation Imaging Package (PIP) observations are presented for numerous case studies to both illustrate the capabilities of these instruments and to document unique radar and concomitant microphysical properties associated with different snowfall modes frequently observed in this region. MRR and PIP observations for a multi-day snow event that locally produced over 90 cm of accumulated snow are presented to illustrate the distinct cloud macrophysical and snow microphysical properties associated with three different distinct phases of this snowfall event (synoptic, lake/orographic enhanced, and lake-effect phases). The MRR observations indicate deep snow-producing cloud structures with a fall streak appearance during the synoptic (or “system”) snow phase, followed by shallow vertically-oriented features embedded within the deeper radar signatures during the lake/orographic enhancement stage. The lake-effect stage is defined by relatively shallow (< 1.5 km deep) convective MRR-observed cloud structures. Snow particle size distributions (PSD) measured by the PIP indicate distinct PSD broadening and systematically larger and less dense particles as the event undergoes the three day transformation. Numerous other case studies documenting typical lake-effect, orographic, and rain-to-snow transitions are also presented to illustrate the varied cold-season precipitation events at this particular site. The value of these ground-based observations for cloud microphysics parameterization improvements and spaceborne remote sensing applications are also presented, including the radar reflectivity to snowfall rate relationship dependence on snowfall mode and seasonal MRR analyses that emphasizes the predominance of shallow snowfall events in the Upper Great Lakes.