MeteoSwiss checks the SwissMetNet monitoring stations in accordance with a stringent certification procedure. This procedure, which is performed by third parties and has been adapted to Switzerland, incorporates numerous criteria defined by the World Meteorological Organization regarding location, the devices and maintenance requirements. The same certification procedure is also applied to stations belonging to partner networks. This ensures that the results generated by different monitoring stations are comparable.
Certification of monitoring stations
As part of the certification procedure, around 80 quality criteria are checked. These are based on the so-called "CIMO Guide", the guidelines of the WMO's Commission for Instruments and Methods of Observations. The principles, which are formulated to create standardisation, have been adjusted to take account of Switzerland's specific characteristics, with a particular focus on the areas of climatology and meteorology. For this reason, the procedure is not suitable for other areas of application such as agricultural meteorology or travel weather for road users; other local criteria apply in these areas.
What is checked during the certification process
Roughly speaking, the criteria can be divided into five areas:
- The measurement and transmission interval of the monitoring station: Does a station take measurements and transmit data every ten minutes? Or are the data only transmitted on an hourly or even daily basis?
- Details on the measurement location: Do the location and measurement height correspond to the recommendations of the WMO for the respective parameters? Has the instrument been set up correctly?
- Assessment of the individual measurement instruments: Does the instrument deliver the degree of accuracy required by the WMO? Is it correctly ventilated and/or heated? Does it also work in snow and hail?
- Calibration, maintenance and upkeep: How often is calibration performed in the laboratory and/or maintenance on site? Does the station have a supervisor who performs regular checks? Are parallel measurements taken and/or are automatic data checks conducted in order to ensure faulty instruments are quickly identified?
- Data analysis: The data analysis is performed by a partner after one year of data deliveries; this primarily examines the completeness of the data and speed of data transmission.
Assessment of monitoring stations
Based on the examination of a station, the measurement instruments are assigned one of the following categories:
- High measurement quality: An instrument fulfils all criteria and the measurement data can be used both for climatology and meteorology.
- Satisfactory measurement quality: An instrument does not fulfil all of the criteria and/or has a lower level of measurement accuracy. The data cannot be used for climatology, but can be used for meteorology and warning purposes.
- Unsatisfactory measurement quality or special location: Individual criteria are seriously violated. This may involve an instrument with a low level of accuracy or relate to a poor location. Alternatively, the station may be located in a special location which fails to meet the WMO criteria. This is the case, for instance, for measurements taken from towers and mountain peaks as well as measurements taken at elevated locations due to high snowfall during the winter. The data should be used with the breached criteria in mind and with the necessary degree of caution.
Introduction of certification and the certification procedure
The integration of partner stations within the MeteoSwiss data warehouse served as the impetus for the development of an independent certification procedure. This step made it essential to introduce an approval process for automatic monitoring stations. Only in this way can the relevant criteria be assessed objectively. This is a pre-requisite for being able to compare the results taken from different stations.
The quality assurance procedure developed by MeteoSwiss is performed by the Federal Office of Metrology (METAS). The independent body certified SwissMetNet and 20 partner stations for the first time in 2013. In doing so, a great deal of useful information was gleaned and subsequently incorporated into the certification procedure. Since 2014, the certification has been a fixed part of the operation of numerous monitoring stations integrated within the MeteoSwiss data warehouse. It is planned to check each station every five years. The results are discussed internally with the operations teams and with the relevant partners; measures aimed at improving the measurement quality are devised and implemented as quickly as possible. The objective is not always to achieve the highest quality level, but rather the level of quality appropriate for the area of application.