Dallas-Fort Worth High Ozone June 20, 2008

• Ozone Animation
• Plume Animation
• Backward Trajectory - CAMS 402 5 pm CDT
• Backward Trajectory - CAMS 402 6 pm CDT
• Satellite Animation
• Satellite Image True Color - Texas 2:04 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 Friday, June 20th.   The highest measured eight-hour ozone average was 93 parts per billion (ppb) at the Dallas Executive Airport Continuous Ambient Monitoring Station (CAMS) 402.   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 106 ppb from 5:00 to 6:00 p.m Central Daylight Time (CDT) also at Dallas Executive Airport CAMS 402.   Five 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 17 sites.   This was the seventh day this year with AQI Level Orange measurements somewhere in the Dallas-Fort Worth area based on the new ozone standard and the fourth day with measurements exceeding the old ozone standard.

Showers and thundershowers moved southeastward through the Dallas-Fort Worth area in the early morning, but skies cleared by late morning and were partly cloudy in the afternoon.   Winds were light from the west around sunrise and gradually shifted to the northwest by late morning and to the north in the afternoon and to the northeast in the evening.   The high temperature reached 98 degrees Fahrenheit (°F) at the Dallas-Fort Worth Airport, 96°F at Dallas Love Field, and 96°F at Fort Worth Meacham Field.

Regional background levels of ozone ranged from about 55 to 61 ppb as indicated by peak eight-hour ozone measurements at Greenville CAMS 1006, Pilot Point CAMS 1032, and Parker CAMS 76.   The difference of about 32 to 38 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 34 to 41 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.