Comparison of modelled and measured total CO and NOx emission rates

Hourly total CO and NOx emission rates determined experimentally from the city of Augsburg, a medium-sized city in southern Germany, were compared with data calculated with a high-resolution emission model. Mass balances based on Aircraft measurements and tracer techniques were used to ascertain real-world emission conditions. On the other hand, comparative emission data were modelled at two different precision levels. A ‘default level’ represents a mesoscale emission model providing emissions highly resolved in time and space as input data for air quality models. Improved activity data obtained by measurements were used for emission calculations at a ‘superior level’. Modelled and measured CO emission rates on working days, in general, were found to be in good agreement. CO emissions on Saturday were slightly underestimated by the model. Modelled NOx emission rates at both levels agree well with the measurements on working days. On Saturday, the modelled NOx emission rates are substantially higher than the measured ones, which represent only some 50–60% of the emission estimates. Comparisons between modelled hourly emissions from point sources and spatially highly resolved Aircraft measurements indicate that the temporal allocation of some industrial activities, especially of specific plants with irregular operating hours are very difficult to reflect by the model.