Sulphate trends in Europe: are we able to model the recent observed decrease?

Abundance of sulphate in Europe has decreased substantially during the last two decades. In this paper, we investigate these recent trends in sulphate concentrations by applying the Oslo CTM2 model using three different sets of SO₂ emission inventories. We perform time slice model simulations with emissions for the years 1985, 1995 and 2000 and compare our results with observations to investigate if there is consistency between measured and modelled sulphate trends. Overall the model reproduces the levels of sulphur and the decreasing sulphate trends reasonably well, although some discrepancies exist. The model shows a strong reduction in the surface concentration of sulphate similar to the observations, although a slightly smaller decrease. Continental and Eastern Europe experience the largest decrease in sulphate from 1985 to 2000; observations give 65 and 63% decrease, respectively, while modelled decreases are from 42 to 58% depending on the inventory. We have also studied to what extent our model results are sensitive and robust. Based on our model simulations we find that the EMEP emissions of the three sets of emission inventories are best to reproduce the trends in sulphate observations.