Ozone and PAN Formation Inside and Outside of the Berlin Plume - Process Analysis and Numerical Process Simulation

Abstract

During the BERLIOZ field phase on 20 July 1998 a 40 km wide ozone-plume 30 to 70 km north of Berlin in the lee of the city was detected. The ozone mixing ratio inside the plume was app. 15 ppb higher than outside, mainly caused by high ozone precursor emissions in Berlin, resulting in a net chemical ozone production of 6.5 ppb h−1, which overcompensates ozone advection of −3.6 ppb h−1 and turbulent diffusion of −1.1 ppb h−1. That means, although more ozone leaves the control volume far in the lee of Berlin than enters it at the leeside cityborder and although turbulent diffusion causes a loss of ozone in the leeside control volume the chemical production inside the volume leads to a net ozone increase. Using a semi-Lagrangian mass budget method to estimate the net ozone production, 5.0 ppb h−1 are calculated for the plume. This means a fraction of about 20% of ozone in the plume is produced by local emissions, therefore called ‘home made’ by the Berlin emissions. For the same area KAMM/DRAIS simulations using an observation based initialisation, results in a net production rate between 4.0 and 6.5 ppb h−1, while the threefold nested EURAD model gives 6.0 ppb h . The process analysis indicates in many cases good agreement (10% or better) between measurements and simulations not only in the ozone concentrations but also with respect to the physical and chemical processes governing the total change. Remaining differences are caused by different resolution in time and space of the models and measurements as well as by errors in the emission calculation.