Weather observation services are adopting non-catching precipitation gauges due to lower maintenance requirements and suitability for automated operation. However, no international standard exists for calibrating this type of rain gauge and for evaluating related measurement uncertainties. The relevant CEN technical committee highlighted a need for a suitable standard, that, if available, could enable generation of more reliable precipitation data, regardless of region, operational network, or instrument technique.

The project established a robust way to evaluate uncertainties relating to rain gauge calibrations. Different types of rain generators have been developed, characterised, tested and compared. A calibration procedure will be studied, developed and validated, and the resulting proposal submitted to the World Meteorological Organisation and CEN TC318, for use in standards. Documented traceability would support the case for innovation in the non-catching gauge market, enabling production of more reliable data and more rigorous assessments of climate change and variability.