Atmospheric Dispersion Modelling

The Royal Dutch Meteorological Institute (KNMI) (Dutch: Koninklijk Nederlands Meteorologisch Instituut) is the Dutch national weather forecasting service and has its headquarters in the town De Bilt, in the province of Utrecht, The Netherlands.

The primary tasks of KNMI are weather forecasting, monitoring of climate changes and monitoring seismic activity. KNMI is also the national research and information centre for climate, climate change and seismology.

Research at KNMI[]

Applied research at KNMI is focused on three areas:[1]

  • Research aimed at improving the quality, usefulness and accessibility of meteorological and oceanographical data in support of operational weather forecasting and other applications of such data.
  • Climate-related research on oceanography; atmospheric boundary layer processes, clouds and radiation; the chemical composition of the atmosphere (e.g. ozone); climate variability research; the analysis of climate, climate variability and climatic change; modelling support and policy support to the Dutch Government with respect to climate and climatic change.
  • Seismological research as well as monitoring of seismic activity (earthquakes).

KNMI's development of atmospheric dispersion models[]

KNMI's applied research also encompasses the development and operational use of atmospheric dispersion models.[2][3]

Whenever a disaster occurs within Europe which causes the accidental release of toxic gases or radioactive material into the atmosphere, it is of utmost importance to quickly determine where the atmospheric plume of toxic material is being transported by the prevailing winds and other meteorological factors. At such times, KNMI activates a special calamity service. For this purpose, a group of seven meteorologists is constantly on call day or night. KNMI's role in supplying information during emergencies is included in municipal and provincial disaster management plans. Civil services, fire departments and the police can be provided with weather and other relevant information directly by the meteorologist on duty, through dedicated telephone connections.

KNMI has available two atmospheric dispersion models for use by their calamity service:

  • PUFF - In cooperation with the Netherlands National Institute for Public Health and the Environment (Dutch: Rijks Instituut voor Volksgezondheid en Milieuhygiene or simply RIVM), KNMI has developed the dispersion model PUFF. It has been designed to calculate the dispersion of air pollution on European scales. The model was orignially tested by using measurements of the dispersion of radioactivity caused by the accident in the nuclear power plant of Chernobyl in 1986. A few years later, in 1994, a dedicated dispersion experiment called ETEX (European Tracer EXperiment) was carried out, which also provided useful data for further testing of PUFF.
  • CALM - CALM is a CALamity Model designed for the calculation of air pollution dispersion on small spatial scales, within the Netherlands. The algorithms and parameters contained in the CALM model are practically identical to that of the PUFF model. However, the meteorological input can only be supplied manually in CALM. The user provides both observed and predicted values for wind velocity at the 10 meter height level, the atmospheric stability classification and the mixing height. After the model calculations have been performed, a map is created and displayed with the derived trajectories of the pollution plume and an indication of how and where the cloud will disperse.


  1. KNMI Research Programme, 2003-2007
  2. Turner, D.B. (1994), Workbook of atmospheric dispersion estimates: an introduction to dispersion modeling, CRC Press, ISBN: 156670023X.
  3. Beychok, Milton R., Fundamentals of Stack Gas Dispersion, (2005), 4th Edition, author-published, ISBN: 0964458802.

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