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04 December 2011

Clouds over the southern Indian Ocean


NASA image acquired November 30, 2011

The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Terra satellite captured this true-color image of a sun-filled, but cloudy day over the southern Indian Ocean on November 30, 2011.

Springtime brings lengthening daylight to the Antarctic, but the increase in sunshine does not necessarily bring cloud-free skies. In fact, winter and spring are considered to be the cloudiest time of year over the southern Indian Ocean.

Clouds in the Antarctic are found most frequently in the boundary layer, which is the lowest atmospheric layer nearest the surface of the Earth, and in the upper tropospheric layer. When air just above the boundary layer is especially stable, this inversion traps the low forming clouds underneath, creating a widespread layer of clouds. In contrast, the upper tropospheric cloud layer tends to peak just above layers of unstable air.

Whether the clouds are low-level or upper level, the form they take is affected by the motion of the atmosphere in a vertical plane, the winds that blow in a horizontal plane, as well as turbulence as air masses mix. In this image, the clouds appear to be affected by all three types of atmospheric motion.

Credit: NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team