Impact of Background Ozone on the Ground-level Oxidant Concentration in the Metropolitan Area (2)

Abstract

Ozone concentrations were measured at inland mountainous region of the Kanto district during a period from April 1983 to April 1984. The impact of background ozone to the ground-level oxidant concentration in the Kanto district was discussed on the basis of the data obtained. A moving averaging method was applied to divide some components with different periods and amplitudes in the observed concentration curve.
The ozone concentration with irregular temporal variation was divided into three parts, i.e., variation with a year period, variation with a few day period and variation with a 24-hour period. The first was suggested to relate the exchange of ozone between stratosphere and troposphere, the second, the transport of background ozone behind cyclonic disturbances and the last, the formation and dispersion of oxidants in the lower atmosphere. Typical seasonal background ozone levels in the Kanto district were estimated as 50 ppb in spring and 25ppb in autumn. A large majority of high oxidant episode generation in the Kanto district was observed within anticyclonic area, and the condition of high oxidant generation was classified into spring type and summer type.