Front cover

Starting end of March, during the bomb attacks over Yougoslavia, at the Web site of the National Institute of Meteorology and Hydrology, prediction for the air transport and dispersion of pollutants from a hypothetical source close to Belgrade was regularly published. The charts were given at the site of the department of Short-Range Forecasting. As a part of the emergency response system in Bulgaria, every day, the wind field at 10 meters above the ground and the near surface concentration fields have been calculated based on the forecast for 12 and 36 hours after midnight. The hypothetical source was assumed to be 300 meters high and typically active for 2 hours at emission of about 100 grams per second (estimated as 1015 conditional units). For quick interpretation of the charts one should know that e.g. the outmost isoline labelled "1" means decrease of concentrations by 1 000 000 times compared with that in the vicinity of the source. Similar activities were performed in other countries of the region as well.