5. Dust Storm in Progress, Maurit

Mauritania has a long coastline blocked by sandbars, but the vast majority of the country’s landmass lies in the desert area of the Western Sahara. Inland from the coastal strip the land is hot and arid. The winter rains are few and the scorching and often violent Harmattan wind blows steadily from the East. In this photograph dust from the dry desert is being transported into the atmosphere by the prevailing winds. The dust can be distinguished from cloud by its smoky appearance and pinkish color. This is an excellent example of a “point source” dust storm, the dust clearly being entrained from discrete points on the desert surface. Other types of dust storm, associated with frontal weather systems, appear to raise long curtains of dust.

The space shuttle provides an excellent platform to observe the progress of dust storms. Shuttle crews have been able to trace the spread of dust palls generated in storms, like the one pictured here, spreading westward far out over the Atlantic, sometimes reaching as far as the Caribbean. Ships in the Atlantic have often recorded the fall of “red rains” from clouds loaded with desert dust.

STS-41G. October 1984. Picture #17-31-016.

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