Altostratus cloud

Type of middle-altitude cloud

Altostratus are middle-altitude clouds that develop horizontally and have a flat and uniform texture in the mid levels. As a middle-altitude cloud type, they can be made up of water droplets (including supercooled droplets), ice crystals, or a mixture of the two. Altostratus clouds usually appear as gray or blueish featureless sheets, although some variants have wavy or banded bases.

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