Dust Dreams .... Yeah it was real.

July 6, 2010 7 PM (left) and July 7, 2010 6 PM (right)

This time approximately 1 year ago, we watched the most amazing event. A large Saharan dust outbreak located 1-3 miles above the ground that nearly blotted the Sun out. Dust you say, yes dust. The Sahara Desert is the largest source of dust in the World. Each year approximately 1 Trillion pounds of dust leaves the Sahara towards the Atlantic, the Mediterranean, Europe and the Middle East. The dust plays an important role in fertilizing the world’s oceans with Iron, which can be taken up by the ocean’s organisms. The dust can travel nearly 3000 miles from Senegal to Barbados during spring and summer seasons. Unfortunately, the dust also causes respiratory problems for many in West Africa and downstream and is one of the leading causes of death in Senegal according to the World Health Organization.

During the summer the dust is suspended above the monsoon layer and only small quantities hit the ground. However, if you are on a flight, you would go right through this dust layer and the ground would not be visible. During the winter, when there is no moist monsoon layer, the dust comes directly to the ground and can be a direct threat to health. The dust also carries the meningitis, which can kill because of its impact on the brain. The Sahel or zone just to the south of the Sahara Desert is the zone during the winter where meningitis is most frequent.

Anyway, this big dust event began on July 5^th in the Southern Algerian Desert and reached Dakar, Senegal during the night of July 7^th, 2010. The Quicktime movie below shows the dust from the MSG satellite with Dust being colored magenta. The next morning, I could not see the Sun directly as it seemed to be covered by clouds. However, it was dust that was above us which was verified by the CALIPSO satellite that viewed the dust layer at about 3 AM in the morning. Our measurements from the ground were off the chart should Aerosol Optical Depth (AOD) approaching 4. This means that most of the direct Sunrays (more than 90%) were being scattered in all directions. At one point, a guy asked me if the Sun was the moon because of the way that it looked.

This year, we have also been looking for these kinds of events. This must happen once in a blue moon as nearly 3 years of measurements to not show AOD approaching a value of 4. This year, the dust seems to be confined more to the North, which may suggest that the monsoon is very far north. We have captured about 4 -5 dust events over the last 3 weeks in Senegal and we did not capture any in Cape Verde during the first two weeks of June. This may mean heavier than normal rains over the next 60 days and also a vigorous hurricane season. I am expecting the switch to turn on within 3 weeks, when strong waves begin coming off the coast. In the meantime, we will continue to search for the big one – Dust event that is.