Saharan dust lingered over Cape Verde in early November 2007, after a few days of dust storm activity off the west coast of Africa. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite took this picture on November 10, 2007. In this image, the dust appears as a semi-transparent swirl blowing over the islands and to the north, curling in a clockwise direction. Over the continent, where dust storm activity has abated, skies are clear.
The long, skinny clouds in the upper left corner of the image are wave clouds, probably caused by the same mass of air blowing the dust. When dry air and moist air meet, the resulting disturbance displaces some air. Along the tops of these waves of air, clouds form. A similar disturbance appeared in May 2007 over the Arabian Sea.