Research Projects

Air quality and meteorological data collected during a three-year period (1989-1991) in the San Francisco Bay Area and surrounding air basins (Broader Sacramento Valley, northern and central portions of the San Joaquin Valley, and the North Central Coast) were analyzed to determine air flow patterns and accompanying meteorological conditions associated with high ozone concentrations in the region. A set of six unique "source- receptor scenarios" were identified. The distinguishing meteorological features of each scenario were explored and used as the basis for the development of an objective procedure for identifying the most appropriate scenario for any given day based on the values of a few key routinely collected meteorological variables. Trajectory analyses were performed for selected days representative of the more common scenarios to determine the principal source-receptor relationships. Favored locations of high ozone concentrations under each scenario were also identified and diurnal profiles of ozone concentrations examined for evidence of interbasin transport of ozone and precursor material. These results provide an improved understanding of the mechanisms that control ozone concentrations in various portions of the study region. The results are particularly useful for the analysis of interbasin transport, air quality trends, and the selection of episodes to be used for photochemical modeling studies.