Mecklenburg County Air Quality (MCAQ) operates three ozone-monitoring sites that span the county from southwest to northeast. The sites operate continuously from April 1 through October 31. Every ten seconds each ozone analyzer measures the ozone concentration in the ambient air.
A computer called a data logger is connected to each analyzer. The computer records each ten second reading. These readings are compiled into one-minute averages and stored. The one-minute averages are compiled into one-hour averages and stored.
The data is downloaded to the MCAQ central computer every hour, which then updates our Air Quality Monitoring page here.
Afternoons Are Unhealthy
Ozone concentrations can reach unhealthy levels when the weather is hot and sunny with relatively light winds. Ozone formation in our area exhibits a diurnal pattern. Ozone levels begin the day at relatively lower levels and rise as the outdoor temperature rises. Concentrations generally peak between noon and six pm. The maximum eight-hour ozone Air Quality Index is typically reported by the SMOGLINE between six and eight pm as the data becomes available.
The three sites operated by MCAQ provide neighborhood and urban scales of representation. The County Line ozone-monitoring site is classified as an urban scale of representation. Urban scale measurements are used to estimate concentrations over large portions of an urban area. The Garinger High School and Arrowood monitoring sites provide information from urban areas characterized by residential and commercial land use and are called neighborhood scale. Under stagnation conditions, a station located in the neighborhood scale may experience peak concentration levels within an urban area.
More information on ground level ozone can be found at USEPA Office of Air and Radiation at http://epa.gov/oar/