The seasonal variation of urban air quality in northern European conditions

Meteorological conditions in northern Europe vary widely with the seasons. Consequently the seasonal variation of urban air pollution is, to a large e xtent, determined by those meteorological variables which are important for air quality. We present first results on the yearly variation of atmospher ic stability land the occurrence of inversion layers), wind velocity, ambie nt temperature, solar radiation, precipitation and snow cover. The seasonal variations of the guideline exceedences for CO, NO2, SO2, TSP and PM10 in urban areas in Finland are then interpreted in the light of the meteorologi cal variation.