Intercomparison of Snowgauges at the Marshall Field Site during the SPICE WMO Field Program

Precipitation is one of the most important atmospheric variables for ecosystem research, hydrological and weather forecasting and climate monitoring. Despite its importance, accurate measurements of precipitation remains a challenge. Measurement errors for solid precipitation, which are often ignored for automated systems, frequently and from 20% to 70% due to undercatch in windy conditions. While solid precipitation measurements have been the subject of many studies, there have been only a limited number of coordinated assessments on the accuracy, reliability, and repeatability of automatic precipitation measurements. The most recent comprehensive study, the “WMO Solid Precipitation Measurement Intercomparison” concluded in 1998 and focused on manual techniques of solid precipitation measurement. Precipitation gauge technology has changed considerably in the last 12 years and the focus has shifted to automated techniques. The Marshall Testbest site is a collaboration between NOAA, NCAR, NWS, and FAA to assess various solid precipitation measurement techniques. This site is being used to test new gauges and other solid precipitation measurement techniques in comparison to reference measurements from gauges with large wind-shields. This paper will highlight efforts to understand the relative accuracies of different instrumentation, gauges and wind-shield configurations to measure snowfall using data from this site. Precipitation measurement devices currently being tested at Marshall Field will be discussed including: wind shields, weighing precipitation gauges, tipping bucket precipitation gauges, and hotplate precipitation gauges. The relationship to the WMO Solid Precipitation InterComparison Experiment (SPICE) for automated snowgauges will also be discussed.