Abstract
Trends in visibility in the urban atmosphere and their relation to the change in consumption of fossil fuels were studied. The data of visibility observed at Nagoya Local Meteorological Observatory at 0900 JST during the period 1945-1977 were used in analysis. According to the relation between the extinction coefficient calculated from visibility in Nagoya and consumption of fossil fuels in the Tokai district including Nagoya, the trends in visibility in the urban atmosphere over Nagoya were closely related to the amount of aerosols originated from the combustion of fossil fuels. It is suggested that the causes of the recovery of visibility after about 1960 were the application of control techniques to the sources of particulate matter and the change in fuel usage from coal to oil. On the basis of the difference in visibility or extinction coefficient as a function of relative humidity between 1960 and 1973, it is suggested that the amount of insoluble matter in aerosols decreased in recent years as a result of the change in fuel usage from coal to oil.
