Ozone and meteorological data were examined for the period May-September 1986-1995 for southeastern lower Michigan. Each day was catalogued as one of nine different synoptic types defined in terms of sea-level pressure, surface vorticity, and windspeed. Ozone concentrations and exceedences (e.g., maximum 8-h average concentrations > 80 ppb) for each of the nine synoptic types were also determined. This synoptic ozone climatology revealed that southwesterly anticyclonic flow occurred 16 percent of the time and accounted for 40 percent of the ozone exceedences. A linear regression formula was also developed using 13 meteorological variables that are typically linked to high ozone levels in general. This formula reproduced ozone values that agreed well with observed ones [r=0.76].
The synoptic climatology procedure and the linear regression formula were then applied to output from the Canadian and Hadley models, two General Circulation Models used during the First US National Assessment, to evaluate how conditions that are favorable for high ozone levels may change by the end of this century. Results from both models suggest that southwesterly flow cases, which correlate with high ozone levels at the present time, may become more frequent and lead to decreased air quality and a possible increase in the reported incidence of respiratory disease.