Modeling atmospheric transport and fate of ammonia in North Carolina-Part I: Evaluation of meteorological and chemical predictions

MM5/CMAQ gave an overall good performance for meteorological variables and O3 mixing ratios and a reasonably good performance for PM2.5. The simulations show that 10-40% of total NH3 was converted to NH4+ at/near source and 40-100% downwind in August, and the conversion rates were 20-50% at/near source and 50-98% downwind in December. While the 3-D atmospheric models demonstrate some skills in capturing synoptic meteorological patterns, diurnal variations of concentrations of oxidants and PM2.5, and regional transport and transformation of NHx, reproducing meteorological and chemical features at a local scale and the magnitudes of hourly concentrations of oxidants and PM2.5 remain challenging due to uncertainties in model inputs and treatments.