Houston High Ozone September 27, 2008

• Ozone Animation
• Plume Animation - Regional
• Back Trajectory CAMS 618 6:00 pm CDT
• Satellite Image False Color - East Texas 2:37 am CDT (from UT CSR)
• Satellite Image False Color - East Texas 10:55 am CDT (from UT CSR)
• Satellite Image True Color - East Texas 11:19 am CDT (from UT CSR)
• Satellite Image False Color - East Texas 1:58 pm CDT (from UT CSR)
• Satellite Image True Color - Houston 11:25 am CDT (from UW SSEC)
• Satellite Image True Color - Houston 2:40 pm CDT (from UW SSEC)

High ozone was measured in the Houston area on Saturday, September 27th.   The highest measured eight-hour average was 93 parts per billion (ppb) at the Danciger Continuous Ambient Monitoring Station (CAMS) 618 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 110 parts per billion (ppb) for the hour from 5:00 to 6:00 p.m. Central Daylight Time (CDT), also at Danciger CAMS 618.   Level Orange ozone was measured at 15 sites, with "Moderate" or higher ozone at all 38 sites reporting complete data for the day. This day was the 28th day with Level Orange or higher ozone measurements, based on the new ozone standard and AQI.   It was the 10th day with measured levels exceeding the old 8-hour ozone standard.

Skies were clear all day. Winds were light from the northwest in the early morning and then shifted to the northeast in the late morning.   Along the coast, winds shifted to the south and southeast with the seabreeze in the afternoon.   The high temperature was 87 degrees Fahrenheit (°F) at George Bush Houston Intercontinental Airport, and 87°F at Hobby Airport.   The Galveston Airport weather station was still down after Hurricane Ike.

Regional background levels of ozone coming into the Houston area were around 61 to 65 ppb as indicated by the peak eight-hour averages at Conroe CAMS 78, Kingwood CAMS 555, and Crosby CAMS 553.   The difference of 28 to 32 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 30 to 34 percent of the measured 93 ppb area eight-hour peak.

The Plume Animation - Regional 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.