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ABSTRACT:The study describes significant outcomes of the 'Metrology for Meteorology' project, MeteoMet, which is an attempt to bridge the meteorological and metrological communities. The concept of traceability, an idea used in both fields but with a subtle difference in meaning, is at the heart of the project. For meteorology, a traceable measurement is the one that can be traced back to a particular instrument, time and location. From a metrological perspective, traceability further implies that the measurement can be traced back to a primary realization of the quantity being measured in terms of the base units of the International System of Units, the SI. These two perspectives reflect long-standing differences in culture and practice and this project -and this study -represents only the first step towards better communication between the two communities. The 3 year MeteoMet project was funded by the European Metrology Research Program (EMRP) and involved 18 European National Metrological Institutes, 3 universities and 35 collaborating stakeholders including national meteorology organizations, research institutes, universities, associations and instrument companies. The project brought a metrological perspective to several long-standing measurement problems in meteorology and climatology, varying from conventional ground-based measurements to those made in the upper atmosphere. It included development and testing of novel instrumentation as well as improved calibration procedures and facilities, instrument intercomparison under realistic conditions and best practice dissemination. Additionally, the validation of historical temperature data series with respect to measurement uncertainties and a methodology for recalculation of the values were included.

Launched in 2011 within the European Metrology Research Programme (EMRP) of EURAMET, the joint research project "MeteoMet" -Metrology for Meteorology -is the largest EMRP consortium: National Metrology Institutes, Universities, meteorological and climate agencies, Research Institutes, collaborators and manufacturers are working together, developing new metrological techniques, as well as improving already existing ones, for meteorological observations and climate records. The project focuses on: humidity in the upper and surface atmosphere, air temperature, surface and deep-sea temperatures, soil moisture, salinity, permafrost temperature, precipitation and snow albedo effect on air temperature. All tasks are performed under rigorous metrological approach and include design and study of new sensors, new calibration facilities, investigation of sensors characteristics, improved techniques for measurements of Essential Climate Variables with uncertainty evaluation, traceability, laboratory proficiency and inclusion of field influencing parameters, long-lasting measurements, and campaigns in remote and extreme areas. MeteoMet vision is to make a further step towards establishing full data comparability, coherency, consistency and long-term continuity, through a comprehensive evaluation of the measurement uncertainties for the quantities involved in the global climate observing systems and the derived observations. The improvement of quality of Essential Climate Variables records, through the inclusion of measurement uncertainty budgets, will also highlight possible strategies for the reduction of the uncertainty. This contribution presents selected highlights of the MeteoMet project and reviews the main ongoing activities, tasks and deliverables, with a view to its possible future evolution and extended impact.

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Infrared ear thermometers (IRETs) are extensively used for measuring the temperature of a human body. For accurate measurements with IRETs they have to be calibrated regularly with an appropriate and traceable calibration system. Such systems are neither widely available nor are there many competent (accredited) laboratories which can provide traceability for IRETs. This paper describes some important influential parameters in the calibration and use of IRETs, which were observed during the extensive research on IRETs and have not been reported in the literature yet. IRET readings, and consequently also their most important metrological characteristics, accuracy and uncertainty of measurement, depend on these influential parameters. According to our findings, we would like to warn users of medical radiation thermometers, not only IRETs but also forehead thermometers and infrared temperature scanning systems, that they should be extremely careful in selection, maintenance and use of medical radiation thermometers. Measurement accuracy, as it is required by several technical standards, is hard to achieve with the majority of currently available medical radiation thermometers.

Self-heating of resistance thermometers is a well-known phenomenon, which occurs when the measuring current additionally heats up the sensing element. In the paper, the self-heating of standard platinum resistance thermometers (SPRTs) is studied with special emphasis on the investigation and evaluation of factors which contribute to the uncertainty of the self-heating correction. The basic two-current method for self-heating correction is analysed and additional correction methods are proposed, based on the optimal selection of currents and the use of more than two different currents. Using the advanced methods we can decrease the uncertainty of the self-heating correction from 0.04 to 0.01 mK. This decrease may not be significant in routine SPRT calibrations, but it can present an improvement in measurements of the highest accuracy, such as intercomparisons.