WMO Interlaboratory Comparison in Europe with Loops Linkage and Data Processing

This article describes the interlaboratory comparison (ILC) of meteorological and hydrological calibration laboratories in the field of temperature (-30 degrees to 40 degrees C), humidity (10%-95% RH at room temperature), and pressure (800-1100 hPa). The ILC was organized by the World Meteorological Organization (WMO) Regional Instrument Centre (RIC) at the Slovenian Environment Agency and University of Ljubljana, Faculty of Electrical Engineering, Laboratory of Metrology and Quality as an accredited interlaboratory comparison (proficiency testing) provider according to the ISO/IEC 17043:2010 standard. The ILC was organized in the target area of WMO Regional Association VI (Europe). The protocol and procedure for ILC were developed within European Metrology Research Project (EMRP) MetoMet2. The participants used their standardized procedures for calibration. Because of the large number of participating laboratories (18) from 17 countries, the ILC was organized in two loops, which were linked via four linking laboratories and evaluated using the E-n number. The equipment used in both loops exhibited stability and uncertainty, which enabled evaluation of the laboratories' capabilities. The article presents the data processing, the linkage procedure, and the main results for all three categories (temperature, humidity, and pressure). It was observed that some of the laboratories had unusually low uncertainties. From the metrological point of view, the authors present some comments and suggestions to the laboratories, the results of which differ from the reference ones. The conclusions can help also other meteorological laboratories and organizations that did not participate in the ILC with their everyday work.