A study of day- and nighttime ozone layers aloft, ozone in national parks, and weather during the SARMAP field campaign

The GATORG-GCMM global-through-urban scale nested air pollution / weather forecast model was applied to study ozone layers aloft, ozone in national parks, and weather during the August 3-6, 1990 SARMAP field campaign in Northern and Central California. Predictions of temperatures, relative humidities, pressures, winds, and mixing ratios of 20 gases were compared with observations. The normalized gross error in near-surface ozone was 22.5% and that in near-surface Kelvin temperatures was 1.02%. The model simulated observed nighttime ozone layers aloft, daytime ozone mixed layers in the San Joaquin Valley and San Francisco Bay Area, and observed daytime and nighttime ozone layers aloft over the San Francisco Bay near Hayward. The formation mechanism of these layers is discussed. The model was further used to estimate that about 47-57 percent of peak daytime ozone in Sequoia and Yosemite National Parks during SARMAP was produced by anthropogenic gases, 13-3 percent was produced by biogenic hydrocarbons, and the rest (about 40 percent) was background.