Applying WRF-CMAQ models for assessment of sulphur and nitrogen deposition in Bulgaria for the years 2016 and 2017

Wet, dry and total depositions of sulphur (S) and nitrogen (N) in Bulgaria are simulated on an annual and seasonal basis for the years 2016 and 2017 using WRF-CMAQ (9 km grid resolution). The mean annual values for wet depositions are about 1,300 kg.km–2, the dry depositions are slightly lower for S and significantly lower for N (180 kg.km–2). The highest modelled wet depositions are in the western and south-western parts of the country, the highest dry depositions – in the northern and eastern parts. The comparison for the wet depositions at three sites with precipitation chemistry data indicates overestimation. A precipitation bias adjustment applied to the modelled depositions results in decrease of the normalised mean bias by a factor of 3. Comparison to modelled deposition data from literature for this region of the country is also provided.