Dallas-Fort Worth High Ozone June 19, 2008

• Ozone Animation
• Plume Animation
• Backward Trajectory - CAMS 75 5 pm CDT
• Backward Trajectory - CAMS 75 6 pm CDT
• Satellite Animation
• Satellite Image True Color - Texas 3:00 pm CDT (from UW SSEC)
• Radar Winds from Palestine
• Radar Winds Mid-Day from Palestine

High ozone was measured on the northwest side of the Dallas-Fort Worth area on Thursday, June 19th.   The highest measured eight-hour ozone average was 85 parts per billion (ppb) at the Eagle Mountain Lake Continuous Ambient Monitoring Station (CAMS) 75.  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 5:00 to 6:00 p.m Central Daylight Time (CDT) also at Eagle Mountain Lake CAMS 75.   Four sites reached AQI Level Orange and exceeded the eight-hour ozone standard, out of 18 sites reporting complete ozone data for the day.   Moderate or higher ozone levels were reported at 10 sites.   This was the sixth day this year with AQI Level Orange measurements somewhere in the Dallas-Fort Worth area based on the new ozone standard and the third day with measurements exceeding the old ozone standard.

Thunderstorms moved southeastward through the Dallas-Fort Worth area in the morning, but skies cleared mid-day.   Winds were gusty and variable with the thunderstorms in the morning and mid-day, but shifted to the east mid-day and then to the southeast later in the afternoon.   The high temperature reached 92 degrees Fahrenheit (°F) at the Dallas-Fort Worth Airport, 89°F at Dallas Love Field, and 90°F at Fort Worth Meacham Field.

Regional background levels of ozone ranged from about 54 to 60 ppb as indicated by peak eight-hour ozone measurements at Greenville CAMS 1006, Kaufman CAMS 71, Italy CAMS 1044, and Cleburne CAMS 77.   The difference of about 25 to 31 ppb between the measured eight-hour area maximum of 85 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 29 to 36 percent of the measured 85 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.