For nuclear emergency response MATCH has been extended with a Lagrangian particle model treating the initial dispersion of pollutants from point sources. The model has been implemented at SMHI in an emergency response system for nuclear accidents and can be activated on short notice to provide forecast concentration and deposition fields. This information is then disseminated to the relevant authorities such as the Swedish Radiation Protection Institute. Meteorological data are taken from operational numerical weather forecasts from the HIRLAM or ECMWF model. The development of the emergency response model is part of the development of a comprehensive decision-aiding system in the European Union project RODOS (Real time Online DecisiOn Support).

The Chernobyl accident prompted a strong development in the field of modelling of accidental releases and long-range transport. The animation below shows an application of the MATCH emergency response model to the historic accident.

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ETEX - European Tracer Experiment
The European Tracer Experiment (ETEX) was established to evaluate the validity of long-range transport models for real-time application in emergency management and to assemble a database which will allow the evaluation of long-range atmospheric dispersion models in general. ETEX main objectives were to conduct a European-scale tracer experiment, and test the capability of institutes responsible for emergency response to forecast in real-time atmospheric dispersion. Following this, the Atmospheric Transport Model Evaluation Study II (ATMES II) simulated the tracer experiment with the same meteorological input data for all models. The animation below shows the calculated concentrations and corresponding observations for the first ETEX release. The circles shows the observations and the colour indicates the observed concentrations.

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Backward adjoint simulation
An adjoint version of MATCH has been developed. The aim is to be able estimate the source characteristics (strength, duration etc.) using observed data from the initial phase of a release. A test of the method has been done using data from the first ETEX release. The adjoint model is run backwards and fed by observations from the ETEX-I experiment. The observations are transported and diffused upstreams and approach slowly the source point, which is situated in Bretagne, France. The release took place from 16 UTC 23 October to 04 UTC 24 October, 1994. The simulation shows the possibility of the adjoint technique to trace source points from observations. The source term may also be derived from the simulation. By using the a priory knowledge of where the release site is the source term could be rather well reconstructed. One key point here is to have access to some observations over a time interval. The technique can make full use of time series of data. As seen in the animation below some observations are not advected towards the release cite. This information could be used to check the confidence of the observations.

Click on the picture to see the animation.