Implementing a dynamical ammonia emission parameterization in the large‐scale air pollution model ACDEP

Currently, very simple parameterizations for the seasonal variation of the ammonia (NH 3 ) emissions are used in most air pollution models. This limits the capability to reproduce observed seasonal variations in the NH 3 concentrations in rural regions with agricultural activity. A dynamical parameterization of the temporal variation of NH 3 emission for application into air pollution models has therefore been proposed. The obtained improvements are demonstrated by implementing a dynamical NH 3 emission parameterization into the large‐scale air pollution model ACDEP. Meteorology, information about agricultural practice, and a simple crop growth model are the basis for the parameterization. Fifteen additive functions are used to describe the different parts of the NH 3 emissions from agriculture, and a 16th function is used to describe NH 3 emission from catalysts used in road traffic. The new parameterization is tested by comparison of model results with NH 3 measurements from Danish monitoring stations situated in agricultural areas during the years 1999–2001. Improvements in correlation coefficient of calculated diurnal mean concentrations from 0.42 to 0.70 have been achieved, and a monthly correlation coefficient up to 0.98 has been obtained for the Tange station in 2000. This validation shows that the new parameterization gives a substantial improvement in the model calculations of the NH 3 concentrations in areas with high agricultural activities. Finally, the validation showed that optimum results are obtained by including a temperature correction on the gauss functions representing the emission sources.