A
stratocumulus cloudA cloud is a visible mass of droplets or frozen crystals suspended in the atmosphere above the surface of the Earth or another planetary body. A cloud is also a visible mass attracted by gravity, such as masses of material in space called interstellar clouds and nebulae...
belongs to a class of clouds characterized by large dark, rounded masses, usually in groups, lines, or waves, the individual elements being larger than those in
altocumuliAltocumulus is a cloud belonging to a class characterized by globular masses or rolls in layers or patches, the individual elements being larger and darker than those of cirrocumulus and smaller than those of stratocumulus. Like other cumulus clouds, altocumulus signifies convection...
, and the whole being at a lower altitude, usually below 2,400 m (8,000 ft). Weak
convectiveConvection is the movement of molecules within fluids . Convection is one of the major modes of heat transfer and mass transfer...
currentsAir currents may be caused by differences in temperature, pressure, or impurity concentration. Temperature differences can cause air currents because warmer air is less dense than cooler air, causing the warmer air to appear "lighter." Thus, if the warm air is under the cool air, air currents will...
create shallow cloud layers because of drier, stable air above preventing continued vertical development.
Vast areas of subtropical and
polarRegions with a polar climate are characterized by a lack of warm summers .The tundra covers over 20% of the earth...
oceanAn ocean is a large body of saline water, and a principal component of the hydrosphere. Approximately 75% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
s are covered with massive sheets of stratocumuli. These may organize into 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 cloudCumulus clouds are a type of cloud with noticeable vertical development and clearly defined edges. Cumulus means "heap" or "pile" in Latin. They are often described as "puffy" or "cotton-like" in appearance. Cumulus clouds may appear alone, in lines, or in clusters...
s, 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.
Most often,stratocumuli produce no precipitation, and when they do, it is generally only light
rainRain is liquid precipitation, as opposed to other kinds of precipitation such as snow, hail and sleet. On Earth, it is the condensation of atmospheric water vapor into drops heavy enough to fall, often making it to the surface...
or
snowSnow is a type of precipitation in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Since snow is composed of small ice particles, it is a granular material. It has an open and therefore soft structure, unless packed by external pressure. Snowflakes...
. 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
thunderheadsA thunderstorm, also known as an electrical storm, a lightning storm, a hailstorm, or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically-assigned cloud type associated with the...
or gusty winds.
These are same in appearance to
altocumuliAltocumulus is a cloud belonging to a class characterized by globular masses or rolls in layers or patches, the individual elements being larger and darker than those of cirrocumulus and smaller than those of stratocumulus. Like other cumulus clouds, altocumulus signifies convection...
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. They are 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 altocumulus.
Stratocumulus perlucidus is a layer of stratocumulus clouds with small spaces, appearing in irregular pattern, through which clear sky or higher clouds can be seen.
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 easily confused: "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 a type of
mammatus cloudMammatus, also known as mammatocumulus, meaning "Mammary cloud" or "Breast cloud" is a meteorological term applied to a cellular pattern of pouches hanging underneath the base of a cloud...
s.
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 cloudCumulus clouds are a type of cloud with noticeable vertical development and clearly defined edges. Cumulus means "heap" or "pile" in Latin. They are often described as "puffy" or "cotton-like" in appearance. Cumulus clouds may appear alone, in lines, or in clusters...
s lose vertical development and spread horizontally.
Stratocumulus diurnalis are formed at lower altitudes (unlike stratocumulus vesperalis) out of
cumulusCumulus clouds are a type of cloud with noticeable vertical development and clearly defined edges. Cumulus means "heap" or "pile" in Latin. They are often described as "puffy" or "cotton-like" in appearance. Cumulus clouds may appear alone, in lines, or in clusters...
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.
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