Compatibility evaluation of national precipitation gage measurements

Abstract

Abstract. Compatibility of precipitation measurements of various national gages commonly used in the Northern Hemisphere countries has been evaluated, based on the gage intercomparison data collected at 10 stations during the World Meteorological Organization (WMO) Solid Precipitation Measurement Intercomparison Project. Little difference (less than 5%) is found between national rainfall data, but a significant discrepancy (up to 110%) exists between national snowfall records.-This difference is not constant and it varies with wind speed and temperature. It is certain that use of different precipitation gages in neighboring countries has introduced a significant discontinuity into precipitation records, particularly in cold and windy regions. Strong linear relations among daily national gage measurements have been defined for several national gages commonly used in the Northern Hemisphere. These linear relations provide a useful technique to adjust gage records when wind speed and temperature data are not available. The linear relations have been tested at selected WMO intercomparison stations, and good agreements of the adjusted amounts to other gage measurements are obtained at most of the test sites, indicating that the linear relations perform reasonably well at the selected WMO sites. Use of the proposed adjustment procedure will reduce inconsistency between precipitation measurements of national gages. IntroductionThere are at least 54 types of precipitation gages currently used in the WMO member countries around the world [Sevruk and Kleinre, 1989], as almost every national weather service has its own method of precipitation observation. These national gages are different in size, shape, material, installation heights, and wind shield used. ]. This study, based on the valuable WMO data set, will quantify the incompatibility of national precipitation measurements of the gages commonly used in the Northern Hemisphere and also present a methodology to adjust the discontinuity. The results of this work will be useful for generating reliable precipitation data sets and climatologies at regional to global scale. Sites, Gages, and Data Sources Methods of Data AnalysisData analysis in this study generally follows the guidelines established by WMO/CIMO [1985, 1993] and focuses on comparison of precipitation measurements by a pair of national gages used in neighboring countries. Wetting loss, evaporation loss, and wind-induced undercatch of precipitation are systematic errors, and they should be corrected in gage catch analysis ]. In this study, bias corrections, however, are not conducted and gage-measured records are used for the analysis. This is because (1) most of the national precipitation archives contain only gage-measured data and (2) the main objective of this work is to evaluate and to quantify the compatibility of precipitation data across national borders.Wind speed at the gage height is required to evaluate the gage catch of precipitation. When wind speed was not measured at the gage height at so...

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