Stratocumulus cloud
Encyclopedia
A Stratocumulus cloud
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 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
ocean
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 cloud
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 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. If the cloud type observed is cirrocumulus followed by altocumulus and then stratocumulus it usually means the approach of a cold front, the next cloud usually being rain-bearing nimbostratus.
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.
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 stratus
. Stratocumulus opacus, if it is seen after perculidus or translucidus, which in turn are seen after altocumulus, usually means the approach of a cold front and rain.
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 perculidus at sunset or sunrise often produces crepuscular rays
.
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, such as Foehn winds, and in this case they can be very regularly shaped.
Stratocumulus castellanus are distincted by puffy tower-like formations atop the atmosphere. 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 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 cloud
s 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.
Cloud
A cloud is a visible mass of liquid droplets or frozen crystals made of water and/or various chemicals suspended in the atmosphere above the surface of a planetary body. They are also known as aerosols. Clouds in Earth's atmosphere are studied in the cloud physics branch of meteorology...
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 altocumuli
Altocumulus cloud
Altocumulus 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 convective
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....
currents
Air current
Air 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 polar
Polar climate
Regions with a polar climate are characterized by a lack of warm summers . Regions with polar climate cover over 20% of the Earth. The sun shines 24 hours in the summer, and barely ever shines at all in the winter...
ocean
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% 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 cloud
Cumulus cloud
Cumulus 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 rain
Rain
Rain is liquid precipitation, as opposed to non-liquid kinds of precipitation such as snow, hail and sleet. Rain requires the presence of a thick layer of the atmosphere to have temperatures above the melting point of water near and above the Earth's surface...
or snow
Snow
Snow is a form of precipitation within the Earth's atmosphere 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...
. 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
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower 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. If the cloud type observed is cirrocumulus followed by altocumulus and then stratocumulus it usually means the approach of a cold front, the next cloud usually being rain-bearing nimbostratus.
These are same in appearance to altocumuli
Altocumulus cloud
Altocumulus 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 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 stratus
Stratus
-Weather:*Stratus cloud, a cloud type**Nimbostratus cloud, a cloud type**Stratocumulus cloud, a cloud type**Altostratus cloud, a cloud type**Altostratus undulatus cloud, a cloud type**Cirrostratus cloud, a cloud type-Music:...
. Stratocumulus opacus, if it is seen after perculidus or translucidus, which in turn are seen after altocumulus, usually means the approach of a cold front and rain.
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 perculidus at sunset or sunrise often produces crepuscular rays
Crepuscular rays
Crepuscular rays , in atmospheric optics, are rays of sunlight that appear to radiate from a single point in the sky. These rays, which stream through gaps in clouds or between other objects, are columns of sunlit air separated by darker cloud-shadowed regions...
.
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, such as Foehn winds, 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 atmosphere. 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 cloud
Mammatus cloud
Mammatus, also known as mammatocumulus , 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 cloud
Cumulus cloud
Cumulus 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 cumulus
Cumulus cloud
Cumulus 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.
External links
- Clouds-Online.com Cloud Atlas with many photos and description of the different cloud genus
- National Science Digital Library - Stratocumulus
- Muriel Martin Online - Stratocumulus Cloud
- WW2010 University of Illinois - Stratocumulus Clouds
- BBC Weather Centre - Types of Cloud - Stratocumulus and Altocumulus