IMPROVEMENT OF THE MODELING OF DAYTIME NITROGEN-OXIDE OXIDATION IN PLUMES BY USING INSTANTANEOUS PLUME DISPERSION PARAMETERS

The effect of concentration fluctuations on the modelling of non-linear chemical reactions in the atmosphere will be considerable when hourly mean dispersion parameters are used. This effect can be reduced by introducing instantaneous dispersion parameters, as will be shown in this paper for the modelling of the oxidation of NO emitted into an O3 containing atmosphere. We used the results of atmospheric tracer gas experiments to derive the dimensions of the instantaneous plume. With these results model calculations were carried out for the NO-O3 reaction. Results were compared with airborne measurements of NO oxidation in the plumes of Dutch power plants. The introduction of the instantaneous plume leads to better agreement between model calculations and measurements. It is also found that the deviation from photochemical equilibrium in the plume is considerably smaller when instantaneous, instead of hourly, mean dispersion parameters are used. The dimension of the instantaneous plume did not show a dependence on atmospheric stability.