Dallas-Fort Worth High Ozone July 1, 2008

• Ozone Animation
• Plume Animation
• Backward Trajectory - Frisco C31 3 pm CDT
• Backward Trajectory - Frisco C31 4 pm CDT
• Backward Trajectory - Pilot Point C1032 6 pm CDT
• Satellite Animation
• Satellite Image True Color - Texas 12:10 pm CDT (from UW SSEC)
• Satellite Image True Color - Dallas/Fort Worth 12:10 pm CDT (from UW SSEC)

High ozone was measured on the north side of the Dallas-Fort Worth area on Tuesday, July 1st.   The highest measured eight-hour ozone average was 93 parts per billion (ppb) at the Frisco Continuous Air Monitoring Station (CAMS) 31.   This measurement rated as Level Orange, Unhealthy for Sensitive Groups, on the U.S. Environmental Protection Agency (EPA) Air Quality Index (AQI) scale.   The highest one-hour ozone measurement was 110 ppb from 3:00 to 4:00 p.m Central Daylight Time (CDT) also at Frisco CAMS 31.   Seven sites reached AQI Level Orange and exceeded the eight-hour ozone standard, out of 19 sites reporting complete ozone data for the day. Moderate or higher ozone levels were reported at 18 sites.   This was the 11th day this year with AQI Level Orange measurements somewhere in the Dallas-Fort Worth area based on the new ozone standard and the sixth day with measurements exceeding the old ozone standard.

Skies were clear most of the day, with a few clouds in the afternoon.   Winds were light from the south in the morning and gradually shifted to the southeast mid-day and in the afternoon at moderate wind speeds.   The high temperature reached 97 degrees Fahrenheit (°F) at the Dallas-Fort Worth Airport, 95°F at Dallas Love Field, and 95°F at Fort Worth Meacham Field.

Regional background levels of ozone ranged from about 66 to 70 ppb as indicated by peak eight-hour ozone measurements at Kaufman CAMS 71, Italy CAMS 1044, and Cleburne CAMS 77.   The difference of about 23 to 27 ppb between the measured eight-hour area maximum of 93 ppb and the approximate regional background level was likely caused by local air pollution sources in the Dallas-Fort Worth area.   The estimated local contribution was about 25 to 29 percent of the measured 93 ppb area eight-hour peak.

The Plume Animation shows the estimated plume tracks from large industrial sources of oxides of nitrogen (NOx) and/or volatile organic compounds (VOC), as well as plume tracks for the center of the broad urban plumes coming from Downtown Dallas, Downtown Fort Worth, and other major urban centers.   The plume animation suggests that urban and industrial emissions from the Dallas area were in the vicinity of the highest ozone measurements.