Air quality index evaluations for Sofia city

Abstract

Some extensive numerical simulations of the atmospheric composition fields in the city of Sofia have been recently performed and 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 US EPA Models-3 system. The meteorological data needed for the models that was used is from the NCEP Global Analysis Data with 1°×1° resolution. The WRF and CMAQ nesting capabilities are applied for downscaling the simulations to a 1 km step for the innermost domain. For Bulgaria and smaller domains the emissions input is from the national emission inventory, prepared by the Ministry of Environment and Water of Bulgaria (MOEW), while outside the country the emissions were taken from the TNO inventory. Special pre-processing procedures are created for introducing temporal profiles and speciation of the emissions. The biogenic emissions of VOC are estimated by the model SMOKE. For describing the ambient pollutant mix, an overall air quality index (AQI) is constructed, which makes it possible to describe the air quality in a simple, understandable for the general public way. The general conclusion that can be made for the Sofia city is that the air quality status of Sofia is not so good (evaluated with a spatial resolution of 1km). AQI status falls mostly in “Low” and “Moderate” bands, but the recurrence of cases with Very High pollution is close to 20% mostly at the city centre.