Texas Saharan Dust
June 17-20, 2004
Images
- PM-2.5 Contour Animation
- Composite Satellite Animation
- Satellite Animation
- Wind Flow June 17
- Wind Flow June 18
- Wind Flow June 19
- Wind Flow June 20
- Back Trajectories June 18
- Back Trajectories June 19
- Back Trajectories June 20
On Thursday, June 17, dense dust from the Saharan desert of Africa entered the southeast coastal areas of Texas. The highest measured daily average PM2.5 level was 46.6 micrograms per cubic meter (µg/m³) at the Brownsville Continuous Ambient Monitoring Station (CAMS) 80 on June 18. This measurement rated as Level Orange Unhealthy For Sensitive Groups on the U.S. Environmental Protection Agency (EPA) Air Quality Index (AQI)
scale. Sites in Corpus Christi, Houston, and Austin also had daily averages in the Unhealthy for Sensitive Groups range on the AQI. Most of the dust had been displaced by cleaner air by June 21st. This Saharan dust event is the only one to reach Level Orange since routine PM2.5 measurements began in Texas in 1999. All of the Saharan dust events during the previous five years reached no higher than Moderate on the AQI. The Saharan dust originates from dust storms caused by high winds over the Saharan Desert and Sub-Saharan areas of northwest Africa and usually takes about one to two weeks to cross the Atlantic Ocean, Carribean Sea, and Gulf of Mexico to reach Texas. Saharan dust events impact Texas mainly from June through August and can last as long as two to three days. About three to six Saharan dust events impact portions of Texas each summer. The Saharan dust may contain allergens that could cause problems for some sensitive people. Speciated PM2.5 measurements indicated high silicon levels in association with the Saharan dust, with daily average concentrations as high as 3.9 µg/m³ at both Houston Aldine and at Big Bend on the 20th.
The Satellite Animation above shows the dust cloud each day as it passed across the Gulf of Mexico. Each image is for 9:09 a.m. Central Daylight Time (CDT). In these satellite images, the dust cloud is outlined with an orange dashed line.
