Open-cell clouds off Peru

Fascinating open- and closed-cell cumulus cloud formations, such as the one featured here, are common off the coast of Peru. In this true-color Terra Moderate Resolution Imaging Spectroradiometer (MODIS) image from August 30, 2003, the formation resembles a running ostrich, with the legs stretching diagonally across the scene from upper left to lower center. The ostrich-shape is made up of lacy open-celled clouds, which occur when air sinks at the center of the cell and rises at the edges. Surrounding the ostrich are closed-celled clouds, where the airflow is reversed: warm air rises at the center (creating cloud particles) and sinks at the edges (leaving clear air). So why do these kinds of clouds form? The reason lies in the fact that the atmosphere, though made up of gasses, behaves like a fluid. The atmosphere can “boil,” or convect, due to heating at the base or cooling at the top of a layer of atmosphere. However, the process is highly chaotic, and there is no apparent way of predicting whether convection will result in open- or closed-cell clouds. Sometimes the atmosphere will flip between one mode and the other in no predictable pattern. Of course, it is the random nature of cloud-formation that makes for such interesting images.