A SYSTEM FOR USING THE AIR RADIOACTIVITY MEASUREMENTS IN A LONG-RANGEMODEL TO FORECAST CLOUD EVOLUTION

The work described aims to make use of all the available information a fter a nuclear accident to improve the forecast of the long range evol ution of the radioactive cloud in the atmosphere. A procedure was deve loped in the past to reduce uncertainties in long range transport mode l predictions mainly due to inputing windfield data to atmospheric tra nsport models which are the result of the forecasts of global or regio nal circulation models. Measurements available in real-time of the air concentrations from national monitoring grids have been used to reduc e the uncertainties. The system is based on a long range transport mod el which can run using a limited amount of meteorological information, and an interpolation routine which generates a new area source from t he air measurements, available in real-time, at ground level. The mode l recalculates the predictions starting from the new source at the tim e when the measurements were performed. The procedure has now been ful ly automated and is available on a PC, with graphical output, to ease its use in emergency situations. The system requires a connection to t he ECMWF network for meteorological input data and to a radiological d ata bank (ECURIE) or national monitoring networks for monitoring data.