Computer Simulations of Atmospheric Composition in Urban Areas. Some Results for the City of Sofia

Some extensive numerical simulations of the atmospheric composition fields in the city of Sofia have been recently performed. An ensemble, comprehensive enough as to provide statistically reliable assessment of the atmospheric composition climate of Sofia—typical and extreme features of the special/temporal behavior, annual means and seasonal variations, etc. has been constructed. The simulations were carried out using the American Environment Protection Agency (US EPA) Models-3 system. As the National Centers for Environmental Prediction (NCEP) Global Analysis Data with 1 degree resolution was used as meteorological background, the system nesting capabilities were applied for downscaling the simulations to a 1 km resolution over Sofia. The national emission inventory was used as an emission input for Bulgaria, while outside the country the emissions were taken from the Netherlands Organization for Applied Scientific research (TNO) inventory. Special pre-processing procedures are created for introducing temporal profiles and speciation of the emissions. The biogenic emissions of Volatile Organic Compound (VOC) are estimated by the model Sparse Matrix Operator Kernel Emissions (SMOKE). The air pollution pattern is formed as a result of interaction of different processes, so knowing the contribution of each for different meteorological conditions and given emission spatial configuration and temporal behavior could be interesting. Different characteristics of the numerically obtained concentration fields of pollutants as well as of determining the contribution of different types of pollutants and pollution sources will be demonstrated in the present paper.