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 ser ies of the diurnal maximum ozone concentration (DMOC) was created in e ach area which was used to examine and analyze the subregional charact eristics 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 intr a-annual perturbation; the inter-annual perturbation; and the synoptic perturbation. The results indicated that all four terms in the time s eries, as well as the number and characteristics of exceedances, Varie d substantially from region to region in the SOS region. Certain aspec ts of the regional variation of the long-term mean could be explained by variations in solar radiation. The variations of the intra-annual p erturbation 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 regio ns was also found which was not expected. The synoptic perturbation is forced by synoptic weather systems. Since the spatial scale of synopt ic weather systems is about 1000 km and the weather characteristics in the systems can change markedly over 1000 km, strong relationships be tween synoptic perturbations from region to region are highly unlikely over a 10 yr period. This suggest that possibly factors other than sy noptic weather systems may have played a role in producing the relatio nship (C) 1998 Elsevier Science Ltd. All rights reserved.