Development and sensitivity analysis of a Lagrangian particle model for long range dispersion

A new long range dispersion model of Lagrangian particle type (MILORD) has been recently developed at the ''Istituto di Cosmogeofisica''. Its capabilities have been tested by comparing its predictions with the Cs-137 air concentrations recorded over Europe by many laboratories during the Chernobyl accident. MILORD sensitivity to variations in its parametrizations has been studied and, in order to ascertain the accuracy of the simulations, some widely used statistical indexes and graphs have been computed. The study has made possible the accomplishment of a set of model input parameters able to produce the best agreement between observations and predictions. It is shown that this model was able to reconstruct with a good accuracy the main characteristics of the radioactive cloud spread over Europe.