Time scales of surface ozone variations in the regional, non-urban environment

A five-year (1985–1989) time series of the average diurnal maximum ozone concentration, O3(t), was developed and examined in each of four 5° latitude by 5° longitude areas in the eastern United States. The time series was divided into four terms: the long-term mean, ; the intra-annual perturbation, A(t′); the inter-annual perturbation, I(t″); and the synoptic perturbation, S(t). The sum of and A(t′) is the mean annual cycle for the daily maximum ozone. In these four areas and in non-urban episode conditions, and S(t) provided the major contribution to the observed daily maximum, accounting for about 70 to 85% of the ozone concentration. However, there were individual instances at certain stations in the four areas when the synoptic perturbation alone contributed as much as 60% to the observed ozone. A(t′) accounted for up to 20% of the observed daily maximum in an episode situation, and I(t″) up to 13% in the ozone season. The results of this study suggest that control strategies focused on reducing the magnitude of and the annual range for A(t′) can reduce the frequency of episodes in the ozone season, but because of large values of S(t) that have been observed, episodic control strategies will also be necessary to completely eliminate episodes.