Texas Saharan Dust July 25-27, 2008

• Backward Air Trajectory 25th
• Backward Air Trajectory 26th
• Backward Air Trajectory 27th
• Satellite Image Gulf of Mexico 23rd 5:15 pm CDT
• Satellite Image Gulf of Mexico 24th 5:15 pm CDT
• Satellite Image Gulf of Mexico 25th 5:15 pm CDT
• Satellite Image Gulf of Mexico 26th 5:15 pm CDT
• Satellite Image Gulf of Mexico 27th 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 spread rapidly across the eastern half of Texas on Friday July 25th and continued over this area through July 27th.  

The highest daily average PM2.5 measurement during this event was 33.7 micrograms per cubic meter (µg/m³) at the Dallas Hinton monitoring site on July 27th.   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 across most of the affected areas on all three 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.   Speciated PM2.5 measurements were only available from a few sites in the eastern half of the state on the 26th, but all of the measurements in this area showed highly elevated levels of silicon indicating dust dominance, ranging from 2.0 µg/m³ at Dallas Hinton to 3.9 µg/m³ at Deer Park.

 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 July 15th, reached the Lesser Antilles on July 20th, and began moving into the Gulf of Mexico on July 23rd. Satellite imagery shows that the dust cloud covered the western half of the Gulf of Mexico on July 24th.