May 4, 2012
Sand at sea, as seen from space
A project comparing data from a research ship with satellite data, this week saw satellite data about dust verified with physical evidence.
Since 11 April EUMETSAT has been part of a project tracking the research ship Polarstern. The ship is cruising from Punta Arenas (Chile) to Bremerhaven (arriving 16 May), taking continuous measurements of atmospheric and marine properties, plus energy and material fluxes between ocean and atmosphere.
This week Polarstern crossed the equator on its journey to Bremerhaven. Although the weather has been calm, the skies have not been clear. Saharan sand has been carried out to sea by an African easterly jet, a specific type of wind pattern. The dust is 1,500m to 6,000m above the ground and at sea it leads to reduced visibility (about 4km). As well as witnessing the reduction in visability, meteorologists on board the ship discovered deposits of sand on deck (pictured below left).
This dust can be seen clearly from space, showing up as pink in top image (below right). The image was produced using a particular set of channels from the MSG satellite, these channels are sensitive to dust in the atmosphere. The dust can also be seen in the visible image (below right, bottom image) as a brown haze over the ocean.
EUMETSAT trainer Mark Higgins, who has been tracking Polarstern, said: "This small amount of dust is not a hazard for the ship, but it shows that we are able to get information about small airborne particles from the satellite data. This allows us to track dust storms (hazardous for people) over land or volcanic ash (a hazard for aircraft) in the air."
This project is a partnership between EUMETSAT and the national weather services of Germany (DWD), Austria (ZAMG) and Portugal (IM), and the Alfred Wegener Institute for Polar and Marine Research (AWI), the operator of the research vessel. EUMETSAT’s international training project EUMETrain is tracking the ship via a special Polarstern portal.
Story on the Polarstern project