Influence of the Grid Resolutions on the Computer Simulated Air Quality Indices over the Territory of Bulgaria

The grid resolution would affect the pollution concentrations and thus on the Air Quality Indices (AQI) - a generalized assessment of the air quality impact on human health. Therefore, we made a numerical experiment for evaluation of the horizontal grid resolution impact on the simulated AQI over the territory of Bulgaria. We used a set of models used worldwide - WRF - the meteorological preprocessor, CMAQ - chemical transport model, SMOKE - emission model for performing computer simulations. The NCEP Global Analysis Data with a horizontal resolution of 1 \(^{\circ }\) \(\times \) 1 \(^{\circ }\) are used as a background meteorological data used in the study. Using the “nesting” capabilities of the WRF and CMAQ models, a resolution of 9 km was achieved for the territory of Bulgaria, by sequentially solving the task in several consecutive, nested areas. The simulations were performed for three cases for grid and emission resolutions for the period 2008–2014, creating an ensemble large and comprehensive enough, reflects the most typical atmospheric conditions with their typical recurrence. The spatial/temporal distribution of the recurrence of the different AQI categories for Bulgaria are calculated. Comparing them for the above 3 cases makes it possible to evaluate the grid resolution impact.