Hundreds of millions of tons of sand and dust particles are lifted from North African deserts each year and carried across the Atlantic Ocean. So much dust is kicked up that the microscopic particles amass into sweeping tan plumes that are visible to satellites.
On February 26, 2015, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite observed some of that dust starting a trans-Atlantic journey. In the image above, vast amounts of dust rise up from Senegal, Mauritania, and Gambia. The plumes are thick and brown, suggesting that he dust is still compact and that it probably arose close to the coastnot from a more distant location in the North African interior.
Some of the dust also appears to be settling into the waters just offshore, adding to the darkening effect in the satellite view. A bit farther offshore, the water surface is brightened by sunglint, the reflection of sunlight directly back at the camera from a relatively smooth surface.
By the next day, the MODIS instrument on NASA’s Terra satellite observed the dust passing over the Cabo Verde Islands (below). The dust cloud was lighter in color, as the coarser, larger sand grains likely dropped out closer to the African coast. Note how the volcanic islands created wake patterns in the dust, as the rough mountain peaks stuck out from the smooth ocean surface and changed the air flow on the leeward side. Low-level dust was probably deposited on the islands, as well.
