From the Latin altum (height) and cumulus (heap). A genus of cloud composed largely of water droplets, and consisting of grey-white sheets, or banded layers and rolls, which may also be broken up into cells. Sometimes it has a banded appearance, occasionally giving a mackerel-sky effect; this is probably associated with strong vertical wind shear in middle altitudes. See also cloud classification.
Subjects: Earth Sciences and Geography — Environmental Science.