The model system (figure 1a and 1b)

A schematic diagram of the model system

The puff coupling

Figures 2-5: Some model results (2-D and 3-D color plots and animations)

ETEX-1 (the European Tracer EXperiment)

2-D animation of ETEX1 (0.1 Mb)

3-D animation of ETEX1 (3 Mb)

2-D animation from the Chernobyl accident (0.6 Mb)

3-D animated illustration of the Chernobyl accident (6Mb)

Depositions from the Chernobyl accident

Participants from NERI/ATMI

Publications

Further information on DREAM

Related home pages at NERI

Abstract

The DREAM (the Danish Rimpuff and Eulerian Accidental release Model) is a comprehensive, high-resolution three-dimensional tracer model, which has been developed for studying short and large scale atmospheric transport, dispersion, and deposition (wet and dry) of radioactive air pollution caused by a single but strong source, as e.g., the Chernobyl accident.

The model is based on a combination of a Lagrangian short-scale puff model and an Eulerian long-range transport model. The Lagrangian model is used in the area near the source to describe the transport, dispersion, and deposition in the initial phase of the release and the Eulerian model is used for long-range transport, dispersion, and deposition calculations in the model domain which covers the whole of Europe. The meteorological meso-scale model MM5V1 is used as a driver for the transport model. A schematic diagram of the model system is illustrated in figure 1a. The coupling between the Lagrangian model and the Eulerian model is performed using the puff coupling, which is illustrated in figure 1b.

The model has been run and validated against the two ATMES-II/ETEX releases (the European Tracer EXperiment) and the Chernobyl accident. Different meteorological input fields and different comprehensive and simple parameterizations of mixing height, dispersion, dry and wet deposition have been included in the model and compared by using numerous statistical tests. Comparisons of model results with measurements have been carried out in connection with the two ETEX releases and the Chernobyl accident. The model is described in many papers (see publications).

For examples of model results, see figures 2-3 and figures 4-5 and the animations in 2-D (click here and here) and 3-D (click here, here and here). The advanced 2-D and 3-D visualization and animation techniques which have been implemented, as e.g. VIS5D and UNIRAS, are important tools for the development of the model, for the validation of the model results and for a better understanding of the different processes studied by the model.

The DREAM model and the visualization techniques are used in two EU-projects: EUROAIR (Esprit no. 24618) and WEPTEL (Esprit no. 22727). The model results obtained by using the DREAM model has been evaluated within ETEX and EKO-4 (Emergency Exercises and Information). The DREAM model is a part of the EUROTRAC subproject GLOREAM. The DREAM model has been supported and funded by the National Environmental Research Institute, Department of Atmospheric Environment, Risø National Laboratory, Wind Energy & Atmospheric Physics, the Danish Research Academy, the Danish Science Research Council, and the Niels Bohr Institute for Astronomy, Physics, and Geophysics, Department of Geophysics, University of Copenhagen.