Cirrus

Cirrus clouds generally refer to atmospheric clouds that are characterized by thin, wisplike strands, often accompanied by tufts, leading to their common (non-standard) name of mare's tail. Sometimes these clouds are so extensive that they are virtually indistinguishable from one another, forming a sheet of cirrus called cirrostratus. Sometimes convection at high altitudes produces another form of cirrus called cirrocumulus, a pattern of small cl... more

Cirrus clouds generally refer to atmospheric clouds that are characterized by thin, wisplike strands, often accompanied by tufts, leading to their common (non-standard) name of mare's tail. Sometimes these clouds are so extensive that they are virtually indistinguishable from one another, forming a sheet of cirrus called cirrostratus. Sometimes convection at high altitudes produces another form of cirrus called cirrocumulus, a pattern of small cloud tufts which include droplets of supercooled water. The term is also used for certain interstellar clouds composed of sub-micrometre sized dust grains. Many cirrus clouds produce hair like filaments made of the heavier ice crystals that precipitate from them. These "fall streaks", a form of virga, often indicate the difference in the motion of air (wind shear) between the upper part of the cirrus cloud and the air below it. Sometimes the top of the cirrus cloud is moving rapidly above a slower layer of air, or the streak is falling into a... less