Smoke concentrations in Athens, Greece: trends and strong episodes, 1984–1991

Daily smoke concentrations measured at four stations in the Athens basin, Greece, for the 8-year period 1984–1991 are studied. The analysis showed that decreasing trends are observed at all these stations, both urban and industrial. Despite the decreasing trends, smoke concentration levels remain high in the Athens basin and over the limit values. Although smoke concentrations present a strong seasonal variation, with a maximum during the cold period of the year and a minimum during the warm period, strong smoke episodes occur during the whole year. Meteorological controls (wind speed, wind direction, temperature, relative humidity, cloudiness and mixing height) on the smoke concentrations during strong episodes were investigated and the results for two of these episodes (one during the cold and one during the warm period of the year) were explicitly analysed. In general, a positive correlation is observed between the smoke concentrations and the temperature, while a negative correlation is observed with wind speed, cloudiness and mixing height.