ABSTRACT
Many air pollution models contain a huge system of equations to cover aerodynamic processes. In principle these equations are not different from hydrodynamics equations, but in practical modeling situations the aerodynamic models are quite different from the hydrodynamics ones, as the considerations on possible simplification will be different. The ammonia emission is computed in parallel and is according to the measured ammonia emission. Over ten minutes for instance, the plume will touch a much broader area, but the concentration will, of course, be correspondingly lower. Numerical models attempt to overcome these weaknesses. They account for wind shear and eddy diffusivity shear and non-linear chemistry. There are two major groups of numerical models: Eulerian multiple box models, which use a fixed coordinate system and Lagrangian trajectory models, which use a moving coordinate system. Weathering processes can, however, be incorporated in the empirical approaches, although the results have little generality, as they are found on basis of regression analysis of local measurements.
