Abstract. Various combinations of wind shields and national precipitation gauges commonly used in countries of the northern hemisphere have been studied in this paper, using the combined intercomparison data collected at 14 sites during the World Meteorological Organization's (WMO) Solid Precipitation Measurement Intercomparison Project. The results show that wind shields improve gauge catch of precipitation, particularly for snow. Shielded gauges, on average, measure 20-70% more snow than unshielded gauges. Without a doubt, the use of wind shields on precipitation gauges has introduced a significant discontinuity into precipitation records, particularly in cold and windy regions. This discontinuity is not constant and it varies with wind speed, temperature, and precipitation type. Adjustment for this discontinuity is necessary to obtain homogenous precipitation data for climate change and hydrological studies. The relation of the relative catch ratio (RCR, ratio of measurements of shielded gauge to unshielded gauge) versus wind speed and temperature has been developed for Alter and Tretyakov wind shields. Strong linear relations between measurements of shielded gauge and unshielded gauge have also been found for different precipitation types. The linear relation does not fully take into account the varying effect of wind and temperature on gauge catch. Overadjustment by the linear relation may occur at those sites with lower wind speeds, and underadjustment may occur at those stations with higher wind speeds. The RCR technique is anticipated to be more applicable in a wide range of climate conditions. The RCR technique and the linear relation have been tested at selected WMO intercomparison stations, and reasonable agreement between the adjusted amounts and the shielded gauge measurements was obtained at most of the sites. Test application of the developed methodologies to a regional or national network is therefore recommended to further evaluate their applicability in different climate conditions. Significant increase of precipitation is expected due to the adjustment particularly in high latitudes and other cold regions. This will have a meaningful impact on climate variation and change analyses.

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...

computed the mean annual basin temperature (T) to be -3.4°C, the mean annual basin precipitation (P) to be 421 mm and the mean annual basin evapotranspiration (E) to be 277 mm. A simple water balance was applied to test the consistency of the P and E fields with the observed basin discharge (Q). For the 24-year period 1972 to 1995, the mean annual residual (P-E-Q) for the water balance was -28.4 mm. This residual is a combination of errors in the three water balance components and the assumption of zero annual storage. It is within the estimation errors associated with the measurement and analysis methods used. Further analysis on the correlation of Q with the total basin net surface moisture supply (P-E) showed that P and (P-E) are most strongly correlated with Q with a 3-month lag, i.e., a discharge water-year of October-September corresponds best with a (P-E) year of July-June. In examining the seasonal correlation of T and E with Q, we found that summer T was significantly correlated with annual Q but there was no significant correlation between any seasonal E or annual Q. This suggests that although the Morton model estimates of E provided a reasonable magnitude for the long-term annual basin water balance, it cannot be considered reliable for year-to-year or shorter-term estimates of the basin evapotranspiration. In examining the 1994/95 water year, it was found to be the lowest discharge year (October-September) in the observed record. This is consistent with the 3-month lagged climate data year (July-June) which for 1994/95 has the largest (P-E) anomaly; it is also the driest year since 1950 having the warmest summer months on record and the third lowest precipitation on record.To demonstrate a practical application of the climate datasets generated by this study, we constructed a multilinear regression model for annual (October-September)

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The phenomena that occurred within and in the vicinity of the