The chemistry of the polluted atmosphere over Europe: Simulations and sensitivity studies with a regional chemistry-transport-model

A model environment has been established, which allows an estimation of the influence of global climate change on the chemistry of the polluted atmosphere over Europe. For this purpose the regional chemistry-transport-model of the EURAD-system has been modified and made adaptable for input data from a regional climate model, which is nested in a global atmospheric circulation model. Thus, the dynamical aspect of a possible global temperature increase as well as enhanced water vapour concentrations and background concentrations of carbon monoxide and methane can be considered. By substituting the meteorological driver model the main problems arise from different vertical grids and physical parameterization schemes. In particular, the parameterization of cloud processes has to be checked to avoid inconsistencies between the chemistry-transport-model and its meteorological driver model. As the length of a simulation period is mainly limited by the large amount of computer time spent for the determination of chemical transformation rates, the gas-phase chemistry module has been optimized concerning computer time and numerical stability. For validation studies of the new model system two episodic simulations were investigated, one for a summer photo-oxidants period in July 1990, the other one for January 1991.