The collection procedure for snow-pan data used by the Society of Automotive Engineers (SAE) international is considered the truth measurement for snowfall liquid water equivalent (LWE) accumulations for winter aviation purposes. To assess these measurements, a study was conducted at the Marshall Field Site in Boulder, Colorado during the 2007-2008 and 2009-2010 winter seasons to compare the manual pan measurements to the different automated precipitation gauges and wind-shield configurations used at the site. Manual pan measurement data was collected from 49 snowstorms with a total of 450.8 hours of observations.

Several automated gauges were used at the site, including the GEONOR T-200B, the OTT Pluvio, and the Hotplate snow gauge. The wind-shields installed at the site were a Double Fenced Intercomparison Reference (DFIR), a standard Alter, and a double Alter, all which were installed around GEONOR gauges. Additionally, the OTT used a Tretyakov-style shield and the Hotplate required no shield.

Snow-pan observations were done using metal pans (30 cm x 50 cm with a 1 cm lip) that were exposed to the precipitation for ten-minute periods. Each pan was weighed before and after exposure to the precipitation so the actual snow LWE accumulation could be calculated. Ten-minute LWE accumulations were calculated from the other automated gauge/shield combinations at the site and the data compared to the snow-pan measurements. Data from the gauge/shield combinations were accumulated over the same ten-minute period as the snow-pans and then compared to the snow-pan data. These comparisons will be presented and conclusions shown regarding the correlation of the automated gauges to the snow-pan measurements.