NATIONAL SCALE DECISION-SUPPORT SYSTEMS - RAPPORTEUR REPORT .1. ATMOSPHERIC DISPERSION MODELING AND RELATED ASPECTS

National scale decision support systems are used to aid decision maker s in taking the appropriate corrective actions to minimise public expo sure to radiation during a nuclear accident. These systems couple envi ronmental radiation measurements and meteorological data with atmosphe ric and radioecological models for predicting the potential public hea lth impacts. The session on Atmospheric Dispersion Modelling and Relat ed Aspects focused on a wide spectrum of atmospheric dispersion models used to support the systems being developed within the US, Japan, Rus sia, UK and Germany. These include gaussian models, three-dimensional wind interpolation models coupled with particle dispersion models, and national weather service operated continental and regional scale fore cast models coupled with dispersion models. One of the limitations of these decision support systems is their inability to quantify the unce rtainties associated with the dispersion model predictions, particular ly when simulating flows over complex terrain, as well as estimating t he heterogeneous deposition patterns resulting from wet deposition pro cesses. This limitation, however, is being addressed by the use of dat a from both local and regional scale tracer experiments for evaluating model performance and the development of numerical techniques for mor e effectively integrating the environmental radiation measurements wit h the model predictions.