El Paso High Ozone June 14, 2008

• Ozone Animation
• Satellite Animation
• Satellite Image - Texas 1:41 pm MDT - True Color (from UW SSEC)
• Winds Aloft at UTEP CAMS 12
• Winds Aloft at UTEP CAMS 12 Mid-day
• Long Range Backward Trajectory - Chamizal C41 2 pm MDT

Description
High ozone was measured in the El Paso - Ciudad Juarez area on Saturday, June 14th.   The highest measured eight-hour average was 87 parts per billion (ppb) at the Ciudad Juarez Delphi Continuous Ambient Monitoring Station (CAMS) 663 on the southeast side of Ciudad Juarez 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 4:00 to 5:00 p.m. Mountain Daylight Time (MDT) also at Juarez Advance CAMS 661.   AQI Level Orange was measured at six sites and AQI "Moderate" or higher ozone was measured at all 14 sites reporting complete ozone data for the day.   This day was the second day this year with Level Orange ozone measurements somewhere in the El Paso - Ciudad Juarez area.

Skies were mostly clear with thundershowers building in the mountains to the east and south of El Paso in the afternoon.   Winds were moderate from the west to west-northwest in the early morning but decreased to light and variable by sunrise and through the afternoon.   The high temperature was 103 degrees Fahrenheit(°F) at the El Paso Intercontinental Airport.

Regional background levels of ozone, in the air coming into the El Paso area, ranged from about 61 to 66 ppb as indicated by the peak eight-hour averages at Santa Teresa, La Union, and Chaparral sites in New Mexico.   The difference of 21 to 26 ppb between the measured eight-hour area maximum of 87 ppb and the approximate regional background level was likely caused by local air pollution sources in the El Paso area.   This approximate local contribution was about 24 to 30 percent of the measured 87 ppb area eight-hour peak.   Long range trajectories indicate that the air arriving in downtown El Paso mid-day had passed across the Phoenix - Tucson area the previous day and emissions from that area may have contributed to increasing the background levels.