Satellites often observe dust swirling over remote and unpopulated deserts but most of these events go largely unnoticed. Not so with the major dust storm that made international news in September 2015 for enveloping heavily-populated areas in the Middle East and North Africa.<br />
Dust first emerged in Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery in Syria on September 6, 2015. By September 7 (top image), a thick plume swept across Syria, the Mafraq region of Jordan, and part of Turkey's Mediterranean coast. By September 8 (bottom image), dust had enveloped all of Lebanon, Israel, Jordan, Cyprus, and the Palestinian Territories. By September 9, it had moved southwest and spread over northeastern Egypt and the Gulf of Suez.<br />
The influx of dust triggered a rash of canceled flights, closed ports, and a suspension of daily activities for many people. In several countries, authorities are advising the elderly and young children to stay indoors. The number of people visiting hospitals with respiratory problems has increased significantly, and several deaths have been attributed to the dust, according to media reports.<br />
While satellites observe the dust from above, air quality sensors on the ground are recording remarkable amounts of particulate matter in surface air. In Jerusalem, pollution levels were 173 times higher than average, according to one news report. A sun photometer at the Sede Boker AERONET station in southern Israel showed a dramatic increase in aerosol optical depth (AOD) - a measure of how much sunlight is scattered by particles in the atmosphere.<br />
"Satellite instruments, particularly MODIS, have revolutionized the scientific community's ability to understand the spatial extent, transport pathways, and the source areas of dust storms," explained Thomas Gill, an atmospheric scientist at the University of Texas at El Paso. "Largely because of MODIS, we now have a much better understanding of what specific kinds of landforms and landscapes