Abstract
Air monitoring data indicates that the average oxidant concentration in Sapporo is higher in April and May than in summer months. According to the auther's analysis, it is found that these spring oxidant peaks are not produced by photochemical reaction near the ground but by the intrusion of stratospheric ozone.
Further, the intrusion of stratospheric ozone into boundary layer may largely contribute to the diurnal variation of oxidants in Sapporo with more than 40 ppb.
A simple photochemical smog model calculation also shows that the distribution of oxidant concentrationin Sapporo is controled by mixing from aloft rather than by photochemical process.
