Shallow mixing depths and ozone variability in urban areas of the U.S

The role of shallow mixing depths in ozone exceedance days is examined for three cities with local ozone production. It is the goal of this study to better understand the role of meteorological conditions, which may lead to improvements in ozone prediction. Ambient ozone data was retrieved for a specific site in each city from April to October during the years 2001-2005 using the EPA Air Quality System. The one-hour National Ambient Air Quality Standard (NAAQS) of 0.12 ppm for ozone was used to identify high ozone events. Boundary layer conditions were examined locally in terms of temperature profiles and vertical velocity plots and regionally through vertical motion and geopotential heights.; The RUC temperature profiles provided a clear indication of shallow mixing depths for Atlanta but were inconclusive for Pasadena. Vertical velocity composites indicated a strong influence of subsidence, which was linked to changes in the large-scale height field.