On December 12, 2016, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this natural-color image of dust over the Arabian Sea. The vortex of clouds and dust is rotating in a direction dictated by Earth’s rotation. In the Northern Hemisphere, this cyclonic rotation is counter-clockwise when looking down from space.
The dust arrived over the sea with a mass of warm desert air—a condition known to suppress cloud formation. It is possible that the warm, dry center of the vortex had not mixed much with the moist marine air surrounding it. The edges of the vortex may have mixed more with the marine air, giving rise to shallow, isolated cumulus clouds.
NASA image courtesy Jeff Schmaltz, MODIS Rapid Response Team at NASA GSFC. Caption by Kathryn Hansen with image interpretation by Andrew Ackerman (NASA GISS) and Toshihisa Matsui (NASA GSFC).