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<br />were similar for Albany and Denver but Clevdand snowfalls produced greater reflectivities. All <br />locations had an optimized exponent of2.0 in the power law. <br /> <br />The SAA produced reasonable estimates of storm-total snow water equivalent for all three areas, highly <br />associated with surface observations. Measur,ements collected in five other climatic regions during the <br />1996-97 winter have yet to be analyzed. <br /> <br />Significant range underestimation was found with Cleveland lake effect storms beyond 70 km. Range <br />underestimation was significantly less with deeper synoptic storms. <br /> <br />Procedures were developed for real-time snow depth estimation after review of fresh snow density <br />observations. Use of nearest neighbor range bins is shown to provide superior snowfall estimates <br />compared to an advection scheme or use of range bin arrays. <br /> <br />The SAA was successfully tested in real-time during the 1996-97 winter at Cleveland and Minneapolis. <br />Customized hybrid scans were required to minimize discontinuities. <br /> <br />Recommended SAA improvements include idtmtification of bright band contamination and a range <br />correction scheme using the vertical profile of reflectivity. <br /> <br />4.3 Snow Density <br /> <br />The SAA estimates SD using SAA calculations of S divided by a declared snow density. Super and <br />Holroyd (1997a) discuss densities of freshly fallen snow. They showed that median densities measured <br />hourly near Albany and Denver, and approximately daily near Cleveland, were in the range of 0.06 to <br />0.08 g cm-3. These values are In good agreement with Doesken and Judson (1996) who showed evidence <br />that, "regardless of location, latitude and elevation, most new snow densities fall in the range from 0.04 <br />to 0.10, with peak frequencies centered between 0.06 and 0.09 \g cm-\" These results show that the <br />commonly used "ten-to-one" rule produces a density (0.1 g cm- ) which is generally too great for the <br />regions studied in this report. <br /> <br />It was investigated whether density could be usefully predicted for the next hour using the current hour's <br />surface air temperature or persistence of density over time. As discussed by Super and Holroyd (1997a), <br />it was concluded that the best approach for SD estimation was to determine the median density based on <br />a large sample of local Sand SD observations. Using the median density, the SAA provides reasonably <br />accurate SD estimates for freshly fallen snow f,or sites protected from the wind. It does not attempt to <br />deal with local SD variations caused by scouring and drifting of already fallen snow, or with the SD of <br />snow which has significantly settled and compacted. <br /> <br />4.4 Single Bins vs Arrays <br /> <br />Reasons for using a single range bin rather than an array of bins were discussed by Super and Holroyd <br />(1997a). Results were very similar using the bin directly over each surface observing location or the <br />array of at least nine bins centered on that location. Moreover, use of a single bin minimizes the spatial <br />averaging problem. The volume sampled by a single bin is already many orders of magnitude larger than <br />sampled by a gage or snow board. <br /> <br />9 <br />