Houston High Ozone June 23, 2008

• Ozone Animation
• Plume Animation
• Plume Animation - Regional
• Backward Air Trajectory 2 pm Wayside C405
• Backward Air Trajectory 3 pm Aldine C8
• Satellite Animation
• Satellite Image True Color - Texas 2:35 pm CDT (from UW SSEC)
• Satellite Image True Color - Houston 2:35 pm CDT (from UW SSEC)
• Winds Aloft at UH La Marque
• Winds Aloft at UH La Marque Mid-Day

Description
High ozone was measured in the Houston area on Monday, June 23rd.   The highest measured eight-hour average was 88 parts per billion (ppb) at the Aldine Continuous Ambient Monitoring Station (CAMS) 8 and rated as Level Orange, Unhealthy for Sensitive Groups, on the U.S. Environmental Protection Agency (EPA) Air Quality Index (AQI) scale.   The highest measured one-hour average was 116 parts per billion (ppb) for the hour from 2:00 to 3:00 p.m. Central Daylight Time (CDT), also at Aldine CAMS 8.   Level Orange ozone was measured at three sites, and "Moderate" or higher ozone at 23 sites out of 40 sites reporting complete data for the day.   This day was the 11th day this year with Level Orange or higher ozone measurements somewhere in the Houston area based on the new 8-hour ozone standard, but only the fourth day with measurements exceeding the old 8-hour ozone standard.

Skies were partly cloudy all day with thundershowers developing in the area in the late afternoon and early evening.   Winds were light from the west to northwest in the early morning and then shifted to the south and southeast in the afternoon with the bay breeze and seabreeze, with gusty and variable winds near the thundershowers.   The high temperature was 97 degrees Fahrenheit (°F) at George Bush Houston Intercontinental Airport, 92°F at Hobby Airport, and 90°F at Galveston Airport.

Background levels of ozone coming into the Houston area were about 46 to 54 ppb as indicated by the peak eight-hour averages at Danciger CAMS 618, Lake Jackson CAMS 1016, and Galveston Airport C1034.   The difference of 34 to 42 ppb between the measured eight-hour area maximum and the approximate regional background level was likely caused by local air pollution sources in the Houston area.   The approximate local contribution was about 39 to 48 percent of the measured 88 ppb area eight-hour peak.

The Plume Animation shows the estimated plume tracks from large industrial sources of oxides of nitrogen (NOx) and volatile organic compounds (VOC), along with the plume tracks for the centers of the broad urban plumes coming from downtown Houston and other major urban centers.   The plume animation suggests that urban and industrial emissions from the Houston Ship Channel area were in the vicinity of some of the highest ozone measurements.