Open-cell clouds in South Atlantic
Jacques Descloitres, MODIS Rapid Response Team, NASA/GSFC
This lacy pattern of open- and closed-cell clouds is caused by heating and cooling in the atmosphere. In "closed" cells, seen primarily in the top right corner of the image, warm air is rising in the center, and sinking around the edges, so clouds appear in cell centers, but evaporate around cell edges. This produces cloud formations like those that dominate the upper right. The reverse flow can also occur: air can sink in the center of the cell and rise at the edge. This process is called "open cell" convection, and clouds form at cell edges around open centers, which creates a lacy, hollow-looking pattern.
Closed and open cell convection represent two stable atmospheric configurations—two sides of the convection coin. But what determines which path the “boiling” atmosphere will take? Apparently the process is highly chaotic, and there appears to be no way to predict whether convection will result in open or closed cells. Indeed, the atmosphere may sometimes flip between one mode and another in no predictable pattern.
The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this image over the South Atlantic on July 20, 2004.