Aspects of subregional ozone variations in the SOS region

The region that was the focus of the Southern oxidant study (SOS) was divided into five 5 degrees latitude by 5 degrees longitude areas (i.e., areas of about 500 km by 500 km) and a 10-year (1981-1990) time series of the diurnal maximum ozone concentration (DMOC) was created in each area which was used to examine and analyze the subregional characteristics of ozone. The time series for the DMOC was divided into four terms: the long-term mean (i.e. the 10 yr mean in this case); the intra-annual perturbation; the inter-annual perturbation; and the synoptic perturbation. The results indicated that all four terms in the time series, as well as the number and characteristics of exceedances, Varied substantially from region to region in the SOS region. Certain aspects of the regional variation of the long-term mean could be explained by variations in solar radiation. The variations of the intra-annual perturbation appear to be correlated with the variations of emissions, and that for the interannual perturbation, with climate fluctuations. A strong relationship between synoptic perturbations in specific regions was also found which was not expected. The synoptic perturbation is forced by synoptic weather systems. Since the spatial scale of synoptic weather systems is about 1000 km and the weather characteristics in the systems can change markedly over 1000 km, strong relationships between synoptic perturbations from region to region are highly unlikely over a 10 yr period. This suggest that possibly factors other than synoptic weather systems may have played a role in producing the relationship (C) 1998 Elsevier Science Ltd. All rights reserved.