Houston High Ozone April 19, 2008

• Ozone Animation
• Plume Animation
• Plume Animation - Regional
• Satellite Animation
• Satellite Image True Color - Southeast Texas 12:20 pm CDT (from NASA)
• Satellite Image True Color - Houston 1:51 pm CDT (from UW SSEC)
• Winds Aloft at La Porte Airport
• Winds Aloft at La Porte Airport Mid-Day
• Winds Aloft at UH La Marque
• Winds Aloft at UH La Marque Mid-Day

Description
High ozone was measured on the north and northeast side of the Houston area and out as far as the Alabama-Coushatta Reservation in Polk County near Livingston on Saturday, April 19th.   The highest measured eight-hour average was 91 parts per billion (ppb) at the Alabama-Coushatta Continuous Ambient Monitoring Station (CAMS) 1027 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 104 parts per billion (ppb) for the hour from 6:00 to 7:00 p.m. Central Daylight Time (CDT), also at Alabama-Coushatta CAMS 1027.   Level Orange ozone was measured at eight of the 41 sites reporting complete data for the day in the Houston metro area and "Moderate" or higher ozone was measured at 39 sites.   This day was the 4th day this year with Level Orange ozone measurements somewhere in the Houston area.

Skies were clear most of the day with scattered high cirrus clouds moving in from the west in the afternoon.   Winds were very light from the south in the early morning and increased to moderate speeds from the south to southwest inland and southeast along the coast during the afternoon.   The high temperature was 83 degrees Fahrenheit (°) at George Bush Houston Intercontinental Airport, 82° at Hobby Airport, and 75° at Galveston Airport.

Regional background levels of ozone, in the air coming into the Houston area, ranged from about 63 to 67 ppb as indicated by the peak eight-hour averages at Danciger CAMS 618, Lake Jackson CAMS 1016, and at Galveston Airport CAMS 1034.   The difference of 24 to 28 ppb between the measured eight-hour area maximum of 91 ppb and the approximate regional background level of 63 to 67 ppb was likely caused by local air pollution sources in the Houston area.   The approximate 24 to 28 ppb local contribution was about 26 to 31 percent of the measured 91 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.