World Meteorological Organization –Instruments and Observing Methods Report No. 109, “Metrological traceability for meteorological sensors illustrated through examples”

In the framework of EMRP (European Metrology Research Program) the project “MeteoMet Metrology for Meteorology” aspires to respond to the questions and needs of meteorological community for traceable measurement and comprehensive in-field uncertainty measurement budgets. The metrological traceability is a property of a measurement result whereby the result can be related to the International System of Units (SI) through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty. To bring this definition into practice the first chain link is the primary reference standard usually maintained in each country by its National Institute of Metrology. The second step in traceability is to compare the instruments to these standards either directly to obtain low calibration uncertainties, or through intermediate secondary standards. This paper explains the primary standards in temperature, humidity and pressure with examples of typical calibration uncertainties at each step in traceability chain, in order to allow instrument’s final users to select an optimal route in accordance with in-situ requested measurement uncertainty.