Modelling of long-range transport of sulphur over Europe: A two-year model run and some model experiments

The long-range transport of sulphur over Europe is quantified using a simple trajectory model with constant mixing height. Results from a model run covering a two-year period shows that average concentrations of sulphur dioxide and particulate sulphate are predicted reasonably well. The calculations confirm that, in most countries in Europe, the deposition of sulphur due to foreign sources represents an important contribution to the total deposition. Seasonal concentration variations are not well predicted with this simple model. The model experiments show that improvements are gained in this respect when a variable mixing height is introduced together with an increased transformation rate to sulphate in summer and a mechanism for exchange of air between the boundary layer and the free troposphere.