South Texas Smoke February 21-22, 2008

• Backward Air Trajectory 21st 6 am CST
• Backward Air Trajectory 21st 12 pm CST
• Backward Air Trajectory 21st 6 pm CST
• Satellite Image Gulf of Mexico 18th
• Satellite Image Gulf of Mexico 19th
• Satellite Image Gulf of Mexico 20th
• Satellite Image Gulf of Mexico 21st

Smoke from agricultural burning in Mexico and Central America moved into the Lower Rio Grande Valley on Thursday February 21st and continued through Friday February 22nd.  

The highest daily average PM2.5 measurement during this event was 19.9 micrograms per cubic meter (µg/m³) at the Mission Continuous Ambient Monitoring Station (CAMS) 43 on the 21st. This measurement rated as Moderate, on the U.S. Environmental Protection Agency (EPA) Air Quality Index (AQI) scale.   PM2.5 measurements were in the "Moderate" range at all of the PM2.5 monitoring sites in the Lower Rio Grande Valley on both days.   The highest one-hour average PM2.5 measured was 34.4 µg/m³ also at Mission CAMS 43 from 8:00 to 9:00 p.m. Central Standard Time (CST) on the 21st.

Backward air trajectories indicate that the air came from northeastern Mexico.   Satellite imagery also shows evidence of widespread haze across the western half of the southwestern Gulf of Mexico on the 20th and 21st in the air mass that eventually moved into the Lower Rio Grande Valley.   The haze appears to be emmanting from coastal areas of Mexico along the southwestern Gulf of Mexico and spreading northward with southerly wind flow.   Fire channel satellite imagery did not show many large fires in the suspect source areas but does not eliminate the possibility of numerous small agricultural fires.   Normal urban emissions in this area do not cause such large scale haze as was evident on the satellite imagery, which is also suggestive of small but numerous fire sources.   Satellite imagery on previous days did not show any evidence of transport of the haze from other areas, which again infers sources along the coast of the southwestern Gulf of Mexico.