Estimating HO Radical Concentrations for the Central California Ozone Study

The Central California Ozone Study (CCOS) is a multi-year program of meteorological and air quality monitoring, emission inventory development, data analysis, and air quality simulation modeling. Among the goals of this study was the execution of a large-scale field study in summer 2000 to acquire a comprehensive database to support modeling and data analysis. The CCOS field measurement program was conducted during a four-month period from 6/1/00 to 9/30/00. Additional data were collected during ozone episodes (intensive operational periods (IOPs)) to better understand the dynamics and chemistry of the formation of high ozone concentrations. Measurements of volatile organic compounds (VOCs) as well as actinic flux measurements were input into a chemical box model employing the Regional Atmospheric Chemistry Mechanism to produce estimates of hydroxyl (HO) concentrations for CCOS. These estimates of HO were compared with those simulated by a full 3-d air quality model.