Houston High Ozone October 2, 2008

• Ozone Animation
• Plume Animation
• Back Trajectory Sheldon CAMS 551 3pm
• Back Trajectory Crosby CAMS 553 4pm
• Back Trajectory Crosby CAMS 553 5pm
• Back Trajectory Atascosita CAMS 560 5pm
• Back Trajectory Atascosita CAMS 560 6pm
• Satellite Animation
• Satellite Image True Color - East Texas 11:37 am CDT (from UT CSR)
• Satellite Image True Color - Houston 11:37 am CDT (from UT CSR)
• Satellite Image True Color - Texas 2:55 pm CDT (from UW SSEC)
• Satellite Image True Color - Houston 2:55 pm CDT (from UW SSEC)
• Winds Aloft at La Porte
• Winds Aloft at La Porte Mid-Day
• Winds Aloft at La Marque
• Winds Aloft at La Marque Mid-Day

High ozone was measured in the Houston area on Thursday, October 2nd.   The highest measured eight-hour average was 104 parts per billion (ppb) at the Crosby Library Continuous Ambient Monitoring Station (CAMS) 553 and rated as Level Red, Unhealthy, on the U.S. Environmental Protection Agency (EPA) Air Quality Index (AQI) scale.   The highest measured one-hour average was 143 parts per billion (ppb) for the hour from 3:00 to 4:00 p.m. Central Daylight Time (CDT), also at Crosby Library CAMS 553.   Level Red ozone was measured only at two sites and Level Orange or higher ozone was measured at 11 sites, with "Moderate" or higher ozone at 30 sites out of 42 sites reporting complete data for the day.   This day was the sixth day this year with Level Red ozone measurements somewhere in the Houston area and the 32nd day with Level Orange or higher ozone measurements, based on the new ozone standard and AQI.   It was the 13th day with measured levels exceeding the old 8-hour ozone standard.

Skies were clear all day.   Winds were light and variable in the morning and increased and from the south to southeast in the afternoon.   The high temperature was 88 degrees Fahrenheit (°F) at George Bush Houston Intercontinental Airport, 87°F at Hobby Airport, and 82°F at Galveston Airport.

Regional background levels of ozone coming into the Houston area were around 56 to 59 ppb as indicated by the peak eight-hour averages at Seabrook CAMS 45, Mustang Bayou CAMS 619, Lake Jackson CAMS 1016, and Danciger CAMS 618.    The difference of 45 to 48 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 54 to 57 percent of the measured 104 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.