True Snowfall -- An evaluation of the double fence intercomparison reference gauge

Based on the analysis of WMO intercomparison data from 1970 through 1990 at the Valdai Hydrological Research Station in Russia, this study found that blowing snow occurred during one-third of the snowfall events greater than 3.0 mm. Wind direction during these events was primarily from the south where a small lake is located. After eliminating the snowfall events during which blowing snow occurred, there remains a systematic difference between the measurements of the bush gauge and the Double Fence Intercomparison Reference (DFIR) gauge, that is, the bush gauge catches more snow than the DFIR. Therefore the correction of the DFIR for wind induced loss is necessary in order to best represent true precipitation. Regression analysis indicates that the most important factor to the correction is mean wind speed during the storm. Correction equations for different types of precipitation have been developed. An example of the application of using the DFIR as a reference standard is demonstrated with two typical North American precipitation gauges.