This true-color Moderate Resolution Imaging Spectroradiometer (MODIS) image from August 16, 2002, was captured off the coast of California over the Pacific Ocean. The image features both open- and closed-cell cumulus cloud patterns. These cells, or parcels of air, often occur in roughly hexagonal arrays in a layer of fluid (the atmosphere often behaves like a fluid) that begins to convect, due to heating at the base or cooling at the top of the layer.In closed cells, like those around the perimeter, warm air is rising in the center, and sinking around the edges, so clouds appear in cell centers, but evaporate around cell edges. 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, creates a lacy, hollow-looking pattern like the clouds in the center of the image. Sensor: Terra/MODIS. Data Start Date: 8/16/02. Data End Date: 8/16/02.