The Frise heated tipping bucket is the standard liquid precipitation accumulation gauge used with the Automated Surface Observing System (ASOS). The sensor measures liquid accumulation, but is not specifically designed to accurately measure freezing or frozen precipitation. The accurate measurement of liquid equivalent accumulations in all types of liquid, solid, and mixed precipitation is an important part of weather observations. The National Weather Service ASOS Product Improvement team has conducted testing of various all-weather precipitation accumulation gauges (AWPAG) since 1996.

A contract for design and development of ten pre-production gauges was awarded on September 25, 2001, to C.C. Lynch and Associates (CCLA) of Pass Christian, Mississippi, in partnership with Ott Hydrometry of Kempten, Germany. Development testing from January 2002 to October 2003 demonstrated significant improvements in gauge catch, accuracy, increased capacity, and communications.

Full production AWPAGs were delivered in October 2003 and included hardware temperature compensation and revised internal sensor algorithm logic to improve gauge sensitivity. Statistical results from subsequent winter testing over the 2003-2004 season of the final AWPAG configuration will be presented in the paper and at the conference.