The World Meteorological Organisation (WMO), a specialised agency of the United Nations, oversees global monitoring of the Earth’s weather. This includes maintaining networks of Automatic Weather Stations (AWS) which measure temperature, humidity and pressure around the world, data which is used to make short term local and national weather forecasts. This data could also be used by climate scientists as a way to monitor long term global climate change trends and assess the effect of mitigation initiatives.
Weather monitoring networks are run independently, by national or supra-national bodies. Each use their own instrumentation and measurement approaches and have their own calibration labs. This works well for local forecasting, but climate researchers need to be sure they are looking at a consistent set of global data between networks.
The WMO runs the Commission for Instruments and Methods of Observation (CIMO) which is responsible for ensuring instrument accuracy across networks. Through this agency, it hopes to harmonise measurements across global networks, so all results are comparable and traceable to the same standard, and have links to the SI. To do so, it needed to develop methods to test the ability of calibration labs to perform reliable and consistent calibrations.
The EMRP Project Metrology for Essential Climate Variables, identified suitable existing instruments for reliably measuring temperature, humidity and pressure, and a protocol for using these to confirm calibrations.
The instruments were identified based on their robust links to the SI, stability over time, and suitability for transportation to different labs around the world without losing accuracy. The project developed a protocol for setting up and using these instruments, which enables the comparison of calibration lab performance using the same instruments as a reference. This allows different AWS networks to compare their calibrations against SI-linked instruments and demonstrate their proficiency.
Following the project, the WMO requested a comparison between national monitoring networks throughout Europe, using the newly developed project protocols. This was performed by the University of Ljubljana, which sent out instruments to European calibration labs and collated the results. The comparison exercise demonstrated that European labs did indeed have good results. Their calibration labs’ approaches can now be shown to be consistent and traceable to the SI, allowing them to confirm harmonised results.
The project derived protocol is now included by the WMO in a new CIMO instrument guide on meteorological instruments and methods of observation that will be rolled out to AWS networks around the world. This will bring all AWS calibration labs in line with each other, creating harmonisation between global temperature, humidity and pressure measurements. As a result, climate scientists will have the confidence they need to use AWS data to inform ongoing climate monitoring and trend predictions. Feeding this additional data into climate models will improve their accuracy and help governments make better informed decisions about the best ways to mitigate and adapt to climate change.
- EMN Climate and Ocean Observation,