The Characteristics of Snow Echo and Falling Snow Observed in the Wasatch Mountains of Utah

This study examines the relationship between the vertical echo structure of snow events and the characteristics of snow particles that fall to the surface. Several different types of snow observations were obtained at the Alta Ski Resort in the Wasatch Mountains of Utah during 40 snow events between November 2011 and April 2012 as part of the Wasatch Hydrometeor Aggregation and Riming Experiment (WASHARX). Observations were made at two sites, the ski base at 2590 m altitude and a cabin at 3000 m altitude. A vertically pointing 24.1 GHz METEK MicroRainRadar collected information at the base location on the profiles of radar reflectivity, Doppler velocity, and spectral width. At the cabin, a Multi-Angle Snowflake Camera obtained fully automated 20 µm-resolution multiple-stereoscopic color photography of hydrometeors and measured their fall speed. Preliminary analysis indicates a wide variety of observed storm echo structures and snow particle habits. Most of the observed snow particles are not pristine crystals but rather show some evidence of riming. Almost all of the snow events exhibit evidence of orographic enhancement in terms of increasing radar reflectivity with decreasing height in the layer from near echo top to ~500 m above ground level. In some storms, the 500 m layer closest to the surface contains decreasing reflectivity with decreasing height, consistent with the partial sublimation of particles in unsaturated air. The analysis of automated high resolution snow particle photography in conjunction with the storm context provided by the vertically-pointing radar will improve understanding of the dynamical and microphysical processes in these snow events.