ACCURACY OF NWS 8-INCH STANDARD NONRECORDING PRECIPITATION GAUGE - RESULTS AND APPLICATION OF WMO INTERCOMPARISON

The standard 8 '' nonrecording precipitation gauge has been used histo rically by the National Weather Service (NWS) as the official precipit ation measurement instrument of the U.S. climate station network. From 1986 to 1992, the accuracy and performance of this gauge (unshielded or with an Alter shield) were evaluated during the WMO Solid Precipita tion Measurement Intercomparison at three stations in the United State s and Russia representing a variety of climate, terrain, and exposure. The double-fence intercomparison reference (DFIR) was the reference s tandard used at all the intercomparison stations in the Intercompariso n project. The Intercomparison data collected at different sites are c ompatible with respect to the catch ratio (gauge measured/DFIR) for th e same gauges, when compared using wind speed at the height of gauge o rifice during the observation period. The effects of environmental fac tors, such as wind speed and temperature, on the gauge catch were inve stigated. Wind speed was found to be the most important factor determi ning gauge catch when precipitation was classified into snow, mixed, a nd rain. The regression functions of the catch ratio versus wind speed at the gauge height on a daily time step were derived for various typ es of precipitation. Independent checks of the equations have been con ducted at these intercomparison stations and good agreement was obtain ed. Application of the correction procedures for wind, wetting loss, a nd trace amounts was made on a daily basis at Barrow, Alaska, for 1958 and 1983, and, on average, the gauge-measured precipitation was incre ased by 20% for rain and 90% for snow.