THE CAUSES OF ELEVATED CONCENTRATIONS OF OZONE IN SAPPORO

In order to investigate the causes of elevated concentrations of O3 in Sapporo which are observed under anticyclonic conditions in spring, we made measurements of O3 concentration at Teine mountain (43°04′N, 141°11′E, 1000m high) in the suburbs of Sapporo simultaneously with measurements of concentrations of HNO3, SO2, SO42-, NO3- and 7Be at ground level in the center of Sapporo in spring 1987. Ozone concentration at Teine mountain showed little diurnal variation. We found remarkably high positive correlation between O3 concentration and temperature at 850 mb, and positive correlation between concentrations of O3 and 7Be. No relationships were found between concentrations of O3 and PAN and between O3 concentration and f{hook}s (gas-particle distribution factor for S species). Backward trajectory on isentropic surface showed that the air parcel, which originally had existed in the western edge of the upper tropospheric cyclone, descended to the lower troposphere. The results indicate that elevated O3 concentrations in Sapporo in spring were mainly caused by downward transport of O3 from the middle troposphere rather than photochemical formation of O3 in the boundary layer (BL). © 1990.