Airborne study of ozone formation over Dallas, Texas

Twelve research fights were performed during August 2005 over the Dallas (Texas) metropolitan area. The primary objective was to estimate the relative contribution of primary emissions from large point sources, i.e., major power plants, compared with mobile sources in terms of O3 production. The distinction between the source types was derived from concurrent measurements of SO2 (tracer for point sources) and CO (tracer for mobile sources) relative to levels of O3 and NOx (the O3 precursor). The flights also examined the vertical structure of the atmosphere and its effect on the dispersion/dilution of the trace gases. During the first half of the study the O3 levels in the Dallas area were relatively low and only during the second half were significantly elevated O3 levels observed. For the latter period the relationship between maximum O3 levels, the air mass chemical age and the O3 yield are evaluated. The results also revealed that mobile sources are the main contributors to the elevated O3 levels in the Dallas area.