Definitions

cloud layer

Stratocumulus cloud

A stratocumulus cloud belongs to a class characterized by large dark, rounded masses, usually in groups, lines, or waves, the individual elements being larger than those in altocumuli, and the whole being at a lower altitude, usually below 2,400 m (8,000 ft). Weak convective currents create shallow cloud layers because of drier, stable air above preventing continued vertical development.

Vast areas of subtropical and polar oceans are covered with massive sheets of stratocumuli. These may organize in to distinctive patterns which are currently under active study. In subtropics, they cover the edges of the horse latitude climatological highs, and reduce the amount of solar energy absorbed in the ocean. When these drift over land the summer heat or winter cold is reduced. 'Dull weather' is a common expression incorporated with overcast stratocumulus days. If the air over land is moist and hot enough they may develop to various cumulus clouds, or, more commonly, the sheets of thick stratocumuli may have a nimbostratus look on them. The distinction here is the amount of rain produced. On drier areas they quickly dissipate over land, resembling cumulus humilis.

Generally, stratocumuli bring only light rain or snow. However, these clouds are often seen at either the front or tail end of worse weather, so may indicate storms to come, in the form of thunderheads or gusty winds.

These are same in appearance to altocumuli and are often mistaken for such. A simple test to distinguish these is to compare the size of individual masses or rolls: when pointing your hand in the direction of the cloud, if the cloud is about the size of your thumb, it is altocumulus; if it is the size of your entire hand, it is stratocumulus.

Classification

Stratocumulus clouds are divided into two primary varieties: Stratocumulus undulatus (wavy) and Stratocumulus cumuliformis (cumulus-like).

Stratocumulus undulatus

Stratocumulus undulatus clouds appear as nearly parallel waves, rolls or separate elongated clouds, without significant vertical development, and usually classified by sky coverage.

Stratocumulus opacus is a dark layer of clouds covering entire sky without any break. However, the cloud sheet is not completely uniform, so that separate cloud bases still can be seen. If the cloud layer becomes grayer to the point when individual clouds can’t be distinguished, stratocumulus turns into nimbostratus.

Stratocumulus perlucidus is a layer of stratocumulus clouds with small spaces, appearing in irregular pattern, where clear sky or higher clouds.

Stratocumulus translucidus consist of separate groups of stratocumulus clouds, with a clear sky (or higher clouds) visible between them. No precipitation in most cases.

Stratocumulus lenticularis are separate flat elongated seed-shaped clouds. They are typical for polar countries or warmer climate during winter seasons. They also can be formed by winds passing hills or mountains, and in this case they can be very regularly shaped.

Stratocumulus cumuliformis

Stratocumulus cumulifomis clouds resemble cumulus clouds, because of significant vertical development. This type of clouds is classified by shape.

Stratocumulus castellanus are distincted by puffy tower-like formations atop the cloud layer. They look like cumulus castellanus, but can be easely distinguished: "towers" of cumulus castellanus grow above separate clouds, whereas in case of stratocumulus castellanus there is always more or less defined layer of clouds. Stratocumulus castellanus may develop into cumulus congestus (and even further into cumulonimbus) under auspicious conditions.

Stratocumulus mammatus are type of mammatus clouds.

Stratocumulus vesperalis the specific type of stratocumulus clouds, are flat and elongated. They form in the evening, when updrafts caused by convection decrease making cumulus clouds lose vertical development and spread horizontally.

Stratocumulus diurnalis are formed at lower altitudes (unlike stratocumulus vesperalis) out of cumulus or cumulonimbus clouds, disrupted by decreasing convection. During formation period, puffy tops of cumulus clouds can protrude from stratocumulus diurnalis for a relatively long time until they completely spread in horizontal direction. Stratocumulus diurnalis appear as lengthy sheet or as group of separate elongated cloud rolls or waves.

See also

Actinoform cloud

External links

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