EURAMET reports as a news story the development of new calibration methods for precipitation gauges, thanks to the EMPIR INCIPIT project (Calibration and accuracy of non-catching instrument to measure liquid/solid atmospheric precipitation).
Atmospheric precipitation, most commonly rain or snow, has been defined by the World Meteorological Organisation (WMO) as an Essential Climate Variable (ECV) and so its measurement is key for studying the effects of climate change.
The most common instruments used to measure precipitation are catching gauges which physically collect precipitation to determine either the volume or mass.
However, due to their direct exposure to the elements, these instruments are affected by harsh environmental conditions - such as very low temperatures or high winds - and require frequent maintenance. They can also underreport precipitation levels due to raindrops sticking to the instrument’s collecting funnel.
To overcome this problem, non-catching gauges such as optical disdrometers, which instead ‘sense’ precipitation, are less affected by these issues and can also provide additional information beyond precipitation intensity alone, such as drop size, distribution and visibility. As they do not need to come into direct contact with the environment, they are also ideal for use in remote or automatic weather stations.
However, because non-catching gauges do not collect precipitation, they cannot be calibrated using a reference flow rate or traditional mass and time traceable standards.
In this context, the completed EMPIR INCIPIT project, coordinated by INRiM, has established a robust way to evaluate uncertainties relating to rain gauge calibrations. Different types of rain generators have been developed, characterised, tested and compared.
This EMPIR project is co-funded by the European Union's Horizon 2020 research and innovation programme and the EMPIR Participating States.