These rays, which stream through gaps in clouds (particularly stratocumulus) or between other objects, are columns of sunlit air separated by darker cloud-shadowed regions.
The effects of this modification on the cloud radiative balance operate in different manner from that of the marine stratocumulus cloud brightening scheme.
But until the late 1990s, scientists had dismissed them as merely a relatively uncommon transitional form between open- and closed-cell formations of stratocumulus clouds.
The best-known is cumulonimbus with mammatus, but the mamma feature is also seen occasionally with cirrus, cirrocumulus, altocumulus, altostratus, and stratocumulus.
