Cloud vortices induced by the Crozet Islands

Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA GSFC, Posted on: Sunday, 7 November 2004, 03:21 CST Download full size image

Ship-wave-shaped wave clouds and cloud vortices ripple and swirl through this image of the Crozet Islands in the Indian Ocean. The ship-wave-shaped clouds are to the left in this image, and look similar to the pattern of waves along a seashore. On the right, the cloud vortices appear in an interlocking pattern of circles. This true-color Aqua MODIS image was acquired on November 2, 2004 Both cloud patterns are the result of the lowest airmass moving over an obstacle - in this case, a set of islands. This movement can form a wave (as seen on the left), and the wave movement can continue for long distances. As the air crested a wave, it cooled, and clouds formed. Then, as the air sank into the trough, the air warmed, and clouds did not form. This pattern repeated itself, with clouds appearing at the peak of every wave. If the air spins instead of rises and sinks, it pulls existing clouds into a spiral form (such as seen on the right).

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