Examination of the Performance of Single Alter Shielded and Unshielded Snow Gauges Using Observations from the Marshall Field Site during the SPICE WMO Field Program and Numerical Model Simulations

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 remain a challenge. Measurement errors for solid precipitation, which are often ignored for automated systems, frequently range 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 advanced considerably in the last 12 years and the focus has shifted to automated techniques. The Marshall Field Site, located southwest of Boulder, Colorado, 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 made by a Double Fence Intercomparison Reference gauge (DFIR). This paper will highlight efforts to understand the catch efficiency of the single Alter shielded snow gauge relative to the DFIR using automated observations at the Marshall Field Site collected during the WMO Solid Precipitation InterComparison Experiment (SPICE) and from numerical model simulations. The use of a single Alter Shield snow gauge and unshielded snow gauge to establish a reference system will also be examined.