The U.S. Climate Reference Network (CRN) is a NOAA sponsored network which is being implemented to provide data for climate monitoring and other applications. Reliable, high quality precipitation data are necessary to detect climate change and to validate climate projections and models. Approximately 100 CRN sites are being installed nationwide. NCDC (National Climate Data Center) has conducted field tests of various precipitation gauges and shields in support of the CRN network since November 2003. These tests are being conducted at research sites at Sterling, VA and at Johnstown, PA. Precipitation gauges being evaluated include the GEONOR, Frise, OTT , AWPAG, TB3, VAISALA and non recording 8 inch gauges. The GEONOR , OTT and VAISALA gauges are weighing gauges while the Frise and TB3 are tipping bucket gauges. Various gauge shields are evaluated including the Alter, Double Alter, Tretyakov , ASOS, SDFIR (Small Double Fence Inter-Comparison Reference) and DFIR (Double Fence Inter-Comparison Reference). A previous paper (AMS 13SMOI Conf. Savannah, June 2005) summarized testing results through May 2005. This paper covers the test period from June 2005 through July 2006. Several significant changes have been made since the initial paper, including the installation of the Vaisala gauge and additional Ott gauges. Results of gauge and gauge/shield comparisons are shown. Results differentiated by temperature and other parameters are also included. Analysis of higher intensity precipitation events as well as long term totals is presented. The performance of the GEONOR gauge, selected as the primary CRN gauge, is of particular interest. Site layouts and equipment descriptions are included .
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