Numerical Simulation of NO_X and CO Mass Budgets as Integral Part of an Experimental Evaluation of Modelled Emission Data for the City of Augsburg (Germany)

Abstract

Emission data belong to the most important input data for Chemistry-TransportModels (CTM) since their quality influences the quality of the model results (Russell and Dennis 2000; Hanna et al. 1998). Only a few studies exist dealing with the assessment of the reliability of emission inventories (Placet et al. 2000; Sawyer et al. 2000; Kuhlwein and Friedrich 2000; Vogel et al. 2000). Therefore, in March and October 1998 experimental campaigns named EVA (Evaluation of Highly Resolved Emission Inventories) had been carried out in the area of the city of Augsburg (Germany) (Slemr et al. 2001). The aim was the evaluation of modeled CO and NO_x emission data of the city using, among other methods, a mass balance technique. The mass budget equation for a chemically reactive air pollutant can be written in a simplified manner as

$$\frac{{\partial M}}{{\partial t}} = \left( {{P_{ADV}} + {P_{TRB}} + {P_E} + {P_{CH}}} \right) - \left( {{L_{ADV}} + {L_{TRB}} + {L_{DEP}} + {L_{CH}}} \right)$$

((1))

It describes the temporal change of the mass M of a species caused by several production (P) and loss (L) processes: horizontal and vertical advective transport (ADV), horizontal and vertical turbulent transport (TRB), emission (E), deposition (DEP), and chemical transformation (CH). The basic idea of the experiments was to derive the CO and NO_x emissions of Augsburg solely from measured advective CO and NO_x fluxes. This intention implied that during the experiments idealized requirements of steady state meteorological and constant emission conditions had to be met.