Export of Pollution from Europe: Seasonal and Interannual Variation
Pollution can undergo long-range transport and impact the tropospheric chemistry thousands of kilometers downwind from the source region. Recently, there is interest in the intercontinental transport (ICT) of pollution between the main industrial regions of the extratropics of the Northern Hemisphere, especially the contribution of foreign pollution to regional episodes of high ozone. We present the results of a modelling investigation of the seasonal and interannual variations in the ICT of pollution from Europe from 1988 to 1997 using the GEOS-CHEM 3-d model of transport and chemistry. The model simulates tropospheric ozone-nitrogen oxides-hydrocarbon chemistry including the radiative and heterogeneous chemical effects of sulfate, sea salt, black carbon, organic carbon, and dust aerosols. It captures interannual variations in transport as it is driven by assimilated meteorological data. We identify the important dynamical transport mechanisms and their seasonal and interannual variations. We consider a number of phenomena which impact the ICT of pollution from Europe: i. the impact of the North Atlantic Oscillation (NAO); ii. the important trends in fossil fuel combustion caused by regulation of emissions in Western Europe and the economic contraction of Eastern Europe; and iii. the interannual variability of boreal forest fires.