Southern Texas Saharan Dust August 11-12, 2008

• Backward Air Trajectory 11th
• Backward Air Trajectory 12th
• Satellite Image Gulf of Mexico 9th 5:15 pm CDT
• Satellite Image Gulf of Mexico 10th 5:15 pm CDT
• Satellite Image Gulf of Mexico 11th 5:15 pm CDT
• Satellite Image Gulf of Mexico 12th 5:15 pm CDT
• Satellite Images Tracking Dust from Africa (download PowerPoint file)
• Daily Midday PM2.5 and Wind Plots

 A large Saharan dust cloud moved over most the southern half of Texas on Monday August 11th and continued in South and Southeast Texas through the 12th.   

The highest daily average PM2.5 measurement during this event was 36.1 micrograms per cubic meter (µg/m³) at the Houston Clinton monitoring site on August 12th.    This measurement rated as Unhealthy for Sensitive Groups, on the proposed U.S. Environmental Protection Agency (EPA) Air Quality Index (AQI) scale.   PM2.5 measurements were in the "Moderate" range across most of the affected areas on both days.   Hourly PM2.5 measurements were generally in the 20 to 40 µg/m³ range largely because of Saharan dust in the affected areas, with higher spikes from local influences at some sites, including Houston Clinton.   Only one speciated PM2.5 measurement was available in the affected area during the event, 1.7 µg/m³ at Brownsville on the 12th, which is highly elevated and indicates dust dominance.

Backward air trajectories indicate that the air came across the Atlantic Ocean. Satellite imagery indicates that the dust cloud began emerging from the coast of Africa on August 1st, reached the Lesser Antilles on August 6th, and began moving into the Gulf of Mexico on August 9th.    Satellite imagery shows that the dust cloud covered much of the Gulf of Mexico on August 11th.