File:Open and Closed Cell Clouds over the Pacific Ocean (MODIS 2023-12-16).jpg

English: On December 14, 2023, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite acquired a true-color image of a gorgeous bank of stratocumulus clouds over the Pacific Ocean. This stunning bank contained several forms of stratocumulus, including closed-cell and open-cell clouds and the less-common form known as actinoform clouds.

Closed-cell clouds look similar to a capped honeycomb from above, stuffed with fluffy-looking clouds in the center. On the other hand, open-celled clouds appear more like empty honeycombs, with a clear center and a thin line of cloud around the hexagonal border of the cell.

The main difference between the two cloud types relates to the flow of air. Moist, warm air rises in the center of closed cells and sinks around the edges. Open-cell clouds have air sinking in the center of cells and rising along the edges. In both cases, clouds form when parcels of warm air rise, expand, and cool enough for water vapor to condense into liquid droplets.

Unlike the previous two types of cloud, actinoform clouds are not built on a hexagonal framework. Instead, they often appear leaf-shaped, radial, or look like a wheel with prominent, cloud-lined spokes. A beautiful example of an actinoform cloud can be seen in the lower right corner of the image.