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Meteorology for nuclear accidents

MeteoSwiss operates the EMER-Met wind analysis and forecasting system for nuclear accidents in Switzerland and neighbouring countries. It consists of a special measurement network and the weather forecast model COSMO-1E. The combination of measurements and model provides important bases for emergency response in Switzerland. These can also be used for major events involving the spread of non-radioactive atmospheric pollutants.


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In close cooperation with the Federal Nuclear Safety Inspectorate (ENSI), MeteoSwiss has developed the EMER-Met (Emergency-Response Meteorology) wind analysis and forecasting system, which began operating at the end of 2009. In 2019, the Federal Office for Civil Protection joined as an additional partner. MeteoSwiss is currently bringing the system up to the latest state of the art. The system includes a large number of special measuring instruments and the COSMO-1E weather forecast model. The combination of precise measurements and high-resolution model forecasts makes it possible to determine wind fields and weather developments around Switzerland's nuclear power stations and those in neighbouring countries and thus to calculate the dispersion of contaminated air masses. Both the ENSI and the National Emergency Operations Centre (NAZ) use the information to assess the current situation. On this basis, the NAZ is able to take measures to protect the population.

Special measuring devices

MeteoSwiss has set up its own monitoring network for EMER-Met, which will be renewed over the next few years. It records the atmosphere above Switzerland's Mittelland region in detail, in particular in the direct vicinity of the Swiss nuclear power stations. The monitoring network comprises three different Monitoring systems.

  • At the sites in Schaffhausen, Payerne and Grenchen, remote sensing instruments – wind profilers, radiometers and wind lidars – continually measure the wind, temperature and humidity from the ground up to an altitude of several kilometres. The wind profiler is a radar that measures the radial velocities along a sequence of vertical and four near-vertical beam pointing directions. On this basis, the horizontal wind speeds for all altitudes up to 8 kilometres above the ground can be calculated. The wind profiler is based on the same measuring principle but uses an eye-safe laser beam instead of a radar beam and measures the wind up to 2 km above ground with higher accuracy. The temperature radiometers derive the temperature from the intensity of the atmosphere's natural microwave radiation.
  • High telecommunications towers stretching 100 to 250 metres above the ground and equipped with meteorological measuring devices are situated on the peaks of the Uetliberg, St. Chrischona and Bantiger.
  • At the nuclear power plant sites, MeteoSwiss also measures turbulence in addition to the usual SwissMetNet parameters.

This special monitoring network is supplemented by the SwissMetNet ground-level monitoring network of MeteoSwiss, which comprehensively records the meteorological parameters close to ground level.

Dispersion calculations with the COSMO-1E forecasting model

The measurements taken by the three wind profilers and by SwissMetNet are fed into the MeteoSwiss local weather forecasting model, COSMO-1E. On a grid network with a horizontal grid box size of 1.1 kilometres, the model calculates the weather developments for the coming 33 hours in the Alpine region every three hours.

The high-resolution wind and precipitation fields of COSMO-1E enable the forecasting of the dispersion of contaminated air masses as well as the washing out and deposition of radioactive substances. MeteoSwiss provides delay-free forecasts for wind and precipitation as well as other meteorological parameters to the Federal Nuclear Safety Inspectorate (ENSI) and dispersion calculations to the National Emergency Operations Centre (NAZ). In parallel to this and working on the basis of the relevant measurements and dispersion calculations, the MeteoSwiss meteorologists is responsible for providing both institutions with advice regarding the current weather situation and further meteorological developments in the event of a nuclear accident.

NADAM: Automatic Dose Alarm and Monitoring Network

In addition to the EMER-Met system, MeteoSwiss also operates the NADAM monitoring network on behalf of the National Emergency Operations Centre (NAZ). More than 60 SwissMetNet stations are equipped with special probes which measure the level of radioactive radiation (local dose rate). Together with the precipitation data, the local snow depths and other meteorological parameters, MeteoSwiss transmits the data to the NAZ every ten minutes. If a specific threshold is exceeded (1 micro-Sv/h), an automatic alarm is triggered at the NAZ.