Altostratus cloud
Encyclopedia
Altostratus is a cloud
belonging to a class characterized by a generally uniform gray to bluish-gray sheet or layer, lighter in color than nimbostratus
and darker than cirrostratus
. The sun can be seen through thin altostratus, but thicker layers can be quite opaque. They can look similar to lower altitude stratus cloud
s.
Altostratus clouds are formed by the rising of a large air mass
that condenses into a cloud. They can produce light precipitation, often in the form of virga
. If the precipitation increases in persistence and intensity, the altostratus cloud may thicken into nimbostratus.
Altostratus most often takes the form of a featureless sheet of cloud but can be wavy (undulatus) as a result of wind shear through the cloud. It can also be fragmented (fibratus) with clear sky visible, which often signals the approach of a weakened warm front.
while flying near the top of the cloud, which indicated that the ice crystals were hexagonal near the top. However, farther down, the ice crystals became more conglomerated
.
that is lifted then condensed
, usually by an incoming frontal system, and they can be found over widespread areas. Their altitude is from 6,500–20,000 feet (2,400–6,100 meters). They are primarily composed of water droplets. They can rise at velocities up to .05 to .1 meters per second (.16 to .33 feet per second). They can also be the result of the thickening of a cirrostratus cloud
. Altostratus is rarely seen alone in the sky, as there is usually some accompanying stratocumulus or stratus fractus underneath it, this being due to the increased moisture beneath the altostratus or cumulus clouds dying as the altostratus dims heat from the sun.
belonging to a class characterized by a generally uniform gray to bluish-gray sheet or layer, lighter in color than nimbostratus
and darker than cirrostratus
. The sun can be seen through thin altostratus, but thicker layers can be quite opaque. They can look similar to lower altitude stratus cloud
s.
Altostratus clouds are formed by the rising of a large air mass
that condenses into a cloud. They can produce light precipitation, often in the form of virga
. If the precipitation increases in persistence and intensity, the altostratus cloud may thicken into nimbostratus.
Altostratus most often takes the form of a featureless sheet of cloud but can be wavy (undulatus) as a result of wind shear through the cloud. It can also be fragmented (fibratus) with clear sky visible, which often signals the approach of a weakened warm front.
while flying near the top of the cloud, which indicated that the ice crystals were hexagonal near the top. However, farther down, the ice crystals became more conglomerated
.
that is lifted then condensed
, usually by an incoming frontal system, and they can be found over widespread areas. Their altitude is from 6,500–20,000 feet (2,400–6,100 meters). They are primarily composed of water droplets. They can rise at velocities up to .05 to .1 meters per second (.16 to .33 feet per second). They can also be the result of the thickening of a cirrostratus cloud
. Altostratus is rarely seen alone in the sky, as there is usually some accompanying stratocumulus or stratus fractus underneath it, this being due to the increased moisture beneath the altostratus or cumulus clouds dying as the altostratus dims heat from the sun.
belonging to a class characterized by a generally uniform gray to bluish-gray sheet or layer, lighter in color than nimbostratus
and darker than cirrostratus
. The sun can be seen through thin altostratus, but thicker layers can be quite opaque. They can look similar to lower altitude stratus cloud
s.
Altostratus clouds are formed by the rising of a large air mass
that condenses into a cloud. They can produce light precipitation, often in the form of virga
. If the precipitation increases in persistence and intensity, the altostratus cloud may thicken into nimbostratus.
Altostratus most often takes the form of a featureless sheet of cloud but can be wavy (undulatus) as a result of wind shear through the cloud. It can also be fragmented (fibratus) with clear sky visible, which often signals the approach of a weakened warm front.
while flying near the top of the cloud, which indicated that the ice crystals were hexagonal near the top. However, farther down, the ice crystals became more conglomerated
.
that is lifted then condensed
, usually by an incoming frontal system, and they can be found over widespread areas. Their altitude is from 6,500–20,000 feet (2,400–6,100 meters). They are primarily composed of water droplets. They can rise at velocities up to .05 to .1 meters per second (.16 to .33 feet per second). They can also be the result of the thickening of a cirrostratus cloud
. Altostratus is rarely seen alone in the sky, as there is usually some accompanying stratocumulus or stratus fractus underneath it, this being due to the increased moisture beneath the altostratus or cumulus clouds dying as the altostratus dims heat from the sun.
belonging to a class characterized by a generally uniform gray to bluish-gray sheet or layer, lighter in color than nimbostratus
and darker than cirrostratus
. The sun can be seen through thin altostratus, but thicker layers can be quite opaque. They can look similar to lower altitude stratus cloud
s.
Altostratus clouds are formed by the rising of a large air mass
that condenses into a cloud. They can produce light precipitation, often in the form of virga
. If the precipitation increases in persistence and intensity, the altostratus cloud may thicken into nimbostratus.
Altostratus most often takes the form of a featureless sheet of cloud but can be wavy (undulatus) as a result of wind shear through the cloud. It can also be fragmented (fibratus) with clear sky visible, which often signals the approach of a weakened warm front.
while flying near the top of the cloud, which indicated that the ice crystals were hexagonal near the top. However, farther down, the ice crystals became more conglomerated
.
that is lifted then condensed
, usually by an incoming frontal system, and they can be found over widespread areas. Their altitude is from 6,500–20,000 feet (2,400–6,100 meters). They are primarily composed of water droplets. They can rise at velocities up to .05 to .1 meters per second (.16 to .33 feet per second). They can also be the result of the thickening of a cirrostratus cloud
. Altostratus is rarely seen alone in the sky, as there is usually some accompanying stratocumulus or stratus fractus underneath it, this being due to the increased moisture beneath the altostratus or cumulus clouds dying as the altostratus dims heat from the sun.
belonging to a class characterized by a generally uniform gray to bluish-gray sheet or layer, lighter in color than nimbostratus
and darker than cirrostratus
. The sun can be seen through thin altostratus, but thicker layers can be quite opaque. They can look similar to lower altitude stratus cloud
s.
Altostratus clouds are formed by the rising of a large air mass
that condenses into a cloud. They can produce light precipitation, often in the form of virga
. If the precipitation increases in persistence and intensity, the altostratus cloud may thicken into nimbostratus.
Altostratus most often takes the form of a featureless sheet of cloud but can be wavy (undulatus) as a result of wind shear through the cloud. It can also be fragmented (fibratus) with clear sky visible, which often signals the approach of a weakened warm front.
while flying near the top of the cloud, which indicated that the ice crystals were hexagonal near the top. However, farther down, the ice crystals became more conglomerated
.
that is lifted then condensed
, usually by an incoming frontal system, and they can be found over widespread areas. Their altitude is from 6,500–20,000 feet (2,400–6,100 meters). They are primarily composed of water droplets. They can rise at velocities up to .05 to .1 meters per second (.16 to .33 feet per second). They can also be the result of the thickening of a cirrostratus cloud
. Altostratus is rarely seen alone in the sky, as there is usually some accompanying stratocumulus or stratus fractus underneath it, this being due to the increased moisture beneath the altostratus or cumulus clouds dying as the altostratus dims heat from the sun.
belonging to a class characterized by a generally uniform gray to bluish-gray sheet or layer, lighter in color than nimbostratus
and darker than cirrostratus
. The sun can be seen through thin altostratus, but thicker layers can be quite opaque. They can look similar to lower altitude stratus cloud
s.
Altostratus clouds are formed by the rising of a large air mass
that condenses into a cloud. They can produce light precipitation, often in the form of virga
. If the precipitation increases in persistence and intensity, the altostratus cloud may thicken into nimbostratus.
Altostratus most often takes the form of a featureless sheet of cloud but can be wavy (undulatus) as a result of wind shear through the cloud. It can also be fragmented (fibratus) with clear sky visible, which often signals the approach of a weakened warm front.
while flying near the top of the cloud, which indicated that the ice crystals were hexagonal near the top. However, farther down, the ice crystals became more conglomerated
.
that is lifted then condensed
, usually by an incoming frontal system, and they can be found over widespread areas. Their altitude is from 6,500–20,000 feet (2,400–6,100 meters). They are primarily composed of water droplets. They can rise at velocities up to .05 to .1 meters per second (.16 to .33 feet per second). They can also be the result of the thickening of a cirrostratus cloud
. Altostratus is rarely seen alone in the sky, as there is usually some accompanying stratocumulus or stratus fractus underneath it, this being due to the increased moisture beneath the altostratus or cumulus clouds dying as the altostratus dims heat from the sun.
belonging to a class characterized by a generally uniform gray to bluish-gray sheet or layer, lighter in color than nimbostratus
and darker than cirrostratus
. The sun can be seen through thin altostratus, but thicker layers can be quite opaque. They can look similar to lower altitude stratus cloud
s.
Altostratus clouds are formed by the rising of a large air mass
that condenses into a cloud. They can produce light precipitation, often in the form of virga
. If the precipitation increases in persistence and intensity, the altostratus cloud may thicken into nimbostratus.
Altostratus most often takes the form of a featureless sheet of cloud but can be wavy (undulatus) as a result of wind shear through the cloud. It can also be fragmented (fibratus) with clear sky visible, which often signals the approach of a weakened warm front.
while flying near the top of the cloud, which indicated that the ice crystals were hexagonal near the top. However, farther down, the ice crystals became more conglomerated
.
that is lifted then condensed
, usually by an incoming frontal system, and they can be found over widespread areas. Their altitude is from 6,500–20,000 feet (2,400–6,100 meters). They are primarily composed of water droplets. They can rise at velocities up to .05 to .1 meters per second (.16 to .33 feet per second). They can also be the result of the thickening of a cirrostratus cloud
. Altostratus is rarely seen alone in the sky, as there is usually some accompanying stratocumulus or stratus fractus underneath it, this being due to the increased moisture beneath the altostratus or cumulus clouds dying as the altostratus dims heat from the sun.
belonging to a class characterized by a generally uniform gray to bluish-gray sheet or layer, lighter in color than nimbostratus
and darker than cirrostratus
. The sun can be seen through thin altostratus, but thicker layers can be quite opaque. They can look similar to lower altitude stratus cloud
s.
Altostratus clouds are formed by the rising of a large air mass
that condenses into a cloud. They can produce light precipitation, often in the form of virga
. If the precipitation increases in persistence and intensity, the altostratus cloud may thicken into nimbostratus.
Altostratus most often takes the form of a featureless sheet of cloud but can be wavy (undulatus) as a result of wind shear through the cloud. It can also be fragmented (fibratus) with clear sky visible, which often signals the approach of a weakened warm front.
while flying near the top of the cloud, which indicated that the ice crystals were hexagonal near the top. However, farther down, the ice crystals became more conglomerated
.
that is lifted then condensed
, usually by an incoming frontal system, and they can be found over widespread areas. Their altitude is from 6,500–20,000 feet (2,400–6,100 meters). They are primarily composed of water droplets. They can rise at velocities up to .05 to .1 meters per second (.16 to .33 feet per second). They can also be the result of the thickening of a cirrostratus cloud
. Altostratus is rarely seen alone in the sky, as there is usually some accompanying stratocumulus or stratus fractus underneath it, this being due to the increased moisture beneath the altostratus or cumulus clouds dying as the altostratus dims heat from the sun.
belonging to a class characterized by a generally uniform gray to bluish-gray sheet or layer, lighter in color than nimbostratus
and darker than cirrostratus
. The sun can be seen through thin altostratus, but thicker layers can be quite opaque. They can look similar to lower altitude stratus cloud
s.
Altostratus clouds are formed by the rising of a large air mass
that condenses into a cloud. They can produce light precipitation, often in the form of virga
. If the precipitation increases in persistence and intensity, the altostratus cloud may thicken into nimbostratus.
Altostratus most often takes the form of a featureless sheet of cloud but can be wavy (undulatus) as a result of wind shear through the cloud. It can also be fragmented (fibratus) with clear sky visible, which often signals the approach of a weakened warm front.
while flying near the top of the cloud, which indicated that the ice crystals were hexagonal near the top. However, farther down, the ice crystals became more conglomerated
.
that is lifted then condensed
, usually by an incoming frontal system, and they can be found over widespread areas. Their altitude is from 6,500–20,000 feet (2,400–6,100 meters). They are primarily composed of water droplets. They can rise at velocities up to .05 to .1 meters per second (.16 to .33 feet per second). They can also be the result of the thickening of a cirrostratus cloud
. Altostratus is rarely seen alone in the sky, as there is usually some accompanying stratocumulus or stratus fractus underneath it, this being due to the increased moisture beneath the altostratus or cumulus clouds dying as the altostratus dims heat from the sun.
Image:Altostratus undulatus at sunrise.jpg|Altostratus undulatus at sunrise
Image:Unusually well defined warm front.jpg|Altostratus opacus at the edge of a warm front
Image:As 1.jpg|Altostratus translucidus with stratocumulus below
Image:Altostratus.jpg|Altostratus translucidus
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...
belonging to a class characterized by a generally uniform gray to bluish-gray sheet or layer, lighter in color than nimbostratus
Nimbostratus cloud
A Nimbostratus cloud is characterized by a formless cloud layer that is almost uniformly dark gray. "Nimbo" is from the Latin word "nimbus", which denotes precipitation. It is generally a stratiform cloud of moderate vertical development that produces precipitation, developing cloud bases between...
and darker than cirrostratus
Cirrostratus cloud
Cirrostratus clouds are thin, generally uniform clouds, composed of ice-crystals. They are difficult to detect and if capable of forming halos the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no haloes if it is thicker cirrostratus fibratus. On the...
. The sun can be seen through thin altostratus, but thicker layers can be quite opaque. They can look similar to lower altitude stratus cloud
Stratus cloud
A stratus cloud is a cloud belonging to a class characterized by horizontal layering with a uniform base, as opposed to convective clouds that are as tall or taller than wide . More specifically, the term stratus is used to describe flat, hazy, featureless clouds of low altitude varying in color...
s.
Altostratus clouds are formed by the rising of a large air mass
Air mass
In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. They are classified according to latitude and their continental or maritime...
that condenses into a cloud. They can produce light precipitation, often in the form of virga
Virga
In meteorology, virga is an observable streak or shaft of precipitation that falls from a cloud but evaporates before reaching the ground. At high altitudes the precipitation falls mainly as ice crystals before melting and finally evaporating; this is usually due to compressional heating, because...
. If the precipitation increases in persistence and intensity, the altostratus cloud may thicken into nimbostratus.
Altostratus most often takes the form of a featureless sheet of cloud but can be wavy (undulatus) as a result of wind shear through the cloud. It can also be fragmented (fibratus) with clear sky visible, which often signals the approach of a weakened warm front.
Description
Altostratus clouds may be composed of either water droplets or ice crystals. In some ice crystal altostratus, very thin, rapidly-disappearing horizontal sheets of water droplets appear at random. The sizes of the ice crystals in the cloud tended to increase as altitude decreased. However, close to the bottom of the cloud, the particles decreased in size again. During the sampling of one cloud, the scientists noted a haloHalo (optical phenomenon)
A halo from Greek ἅλως; also known as a nimbus, icebow or gloriole) is an optical phenomenon produced by ice crystals creating colored or white arcs and spots in the sky. Many are near the sun or moon but others are elsewhere and even in the opposite part of the sky...
while flying near the top of the cloud, which indicated that the ice crystals were hexagonal near the top. However, farther down, the ice crystals became more conglomerated
Conglomerate (geology)
A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts...
.
Formation
Altostratus is caused by a large air massAir mass
In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. They are classified according to latitude and their continental or maritime...
that is lifted then condensed
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
, usually by an incoming frontal system, and they can be found over widespread areas. Their altitude is from 6,500–20,000 feet (2,400–6,100 meters). They are primarily composed of water droplets. They can rise at velocities up to .05 to .1 meters per second (.16 to .33 feet per second). They can also be the result of the thickening of a cirrostratus cloud
Cirrostratus cloud
Cirrostratus clouds are thin, generally uniform clouds, composed of ice-crystals. They are difficult to detect and if capable of forming halos the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no haloes if it is thicker cirrostratus fibratus. On the...
. Altostratus is rarely seen alone in the sky, as there is usually some accompanying stratocumulus or stratus fractus underneath it, this being due to the increased moisture beneath the altostratus or cumulus clouds dying as the altostratus dims heat from the sun.
External links
- Clouds-Online.com Cloud Atlas with many photos and description of the different cloud genus
- National Science Digital Library - Altostratus
Gallery
Altostratus is a cloudCloud
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...
belonging to a class characterized by a generally uniform gray to bluish-gray sheet or layer, lighter in color than nimbostratus
Nimbostratus cloud
A Nimbostratus cloud is characterized by a formless cloud layer that is almost uniformly dark gray. "Nimbo" is from the Latin word "nimbus", which denotes precipitation. It is generally a stratiform cloud of moderate vertical development that produces precipitation, developing cloud bases between...
and darker than cirrostratus
Cirrostratus cloud
Cirrostratus clouds are thin, generally uniform clouds, composed of ice-crystals. They are difficult to detect and if capable of forming halos the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no haloes if it is thicker cirrostratus fibratus. On the...
. The sun can be seen through thin altostratus, but thicker layers can be quite opaque. They can look similar to lower altitude stratus cloud
Stratus cloud
A stratus cloud is a cloud belonging to a class characterized by horizontal layering with a uniform base, as opposed to convective clouds that are as tall or taller than wide . More specifically, the term stratus is used to describe flat, hazy, featureless clouds of low altitude varying in color...
s.
Altostratus clouds are formed by the rising of a large air mass
Air mass
In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. They are classified according to latitude and their continental or maritime...
that condenses into a cloud. They can produce light precipitation, often in the form of virga
Virga
In meteorology, virga is an observable streak or shaft of precipitation that falls from a cloud but evaporates before reaching the ground. At high altitudes the precipitation falls mainly as ice crystals before melting and finally evaporating; this is usually due to compressional heating, because...
. If the precipitation increases in persistence and intensity, the altostratus cloud may thicken into nimbostratus.
Altostratus most often takes the form of a featureless sheet of cloud but can be wavy (undulatus) as a result of wind shear through the cloud. It can also be fragmented (fibratus) with clear sky visible, which often signals the approach of a weakened warm front.
Description
Altostratus clouds may be composed of either water droplets or ice crystals. In some ice crystal altostratus, very thin, rapidly-disappearing horizontal sheets of water droplets appear at random. The sizes of the ice crystals in the cloud tended to increase as altitude decreased. However, close to the bottom of the cloud, the particles decreased in size again. During the sampling of one cloud, the scientists noted a haloHalo (optical phenomenon)
A halo from Greek ἅλως; also known as a nimbus, icebow or gloriole) is an optical phenomenon produced by ice crystals creating colored or white arcs and spots in the sky. Many are near the sun or moon but others are elsewhere and even in the opposite part of the sky...
while flying near the top of the cloud, which indicated that the ice crystals were hexagonal near the top. However, farther down, the ice crystals became more conglomerated
Conglomerate (geology)
A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts...
.
Formation
Altostratus is caused by a large air massAir mass
In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. They are classified according to latitude and their continental or maritime...
that is lifted then condensed
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
, usually by an incoming frontal system, and they can be found over widespread areas. Their altitude is from 6,500–20,000 feet (2,400–6,100 meters). They are primarily composed of water droplets. They can rise at velocities up to .05 to .1 meters per second (.16 to .33 feet per second). They can also be the result of the thickening of a cirrostratus cloud
Cirrostratus cloud
Cirrostratus clouds are thin, generally uniform clouds, composed of ice-crystals. They are difficult to detect and if capable of forming halos the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no haloes if it is thicker cirrostratus fibratus. On the...
. Altostratus is rarely seen alone in the sky, as there is usually some accompanying stratocumulus or stratus fractus underneath it, this being due to the increased moisture beneath the altostratus or cumulus clouds dying as the altostratus dims heat from the sun.
External links
- Clouds-Online.com Cloud Atlas with many photos and description of the different cloud genus
- National Science Digital Library - Altostratus
Gallery
Altostratus is a cloudCloud
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...
belonging to a class characterized by a generally uniform gray to bluish-gray sheet or layer, lighter in color than nimbostratus
Nimbostratus cloud
A Nimbostratus cloud is characterized by a formless cloud layer that is almost uniformly dark gray. "Nimbo" is from the Latin word "nimbus", which denotes precipitation. It is generally a stratiform cloud of moderate vertical development that produces precipitation, developing cloud bases between...
and darker than cirrostratus
Cirrostratus cloud
Cirrostratus clouds are thin, generally uniform clouds, composed of ice-crystals. They are difficult to detect and if capable of forming halos the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no haloes if it is thicker cirrostratus fibratus. On the...
. The sun can be seen through thin altostratus, but thicker layers can be quite opaque. They can look similar to lower altitude stratus cloud
Stratus cloud
A stratus cloud is a cloud belonging to a class characterized by horizontal layering with a uniform base, as opposed to convective clouds that are as tall or taller than wide . More specifically, the term stratus is used to describe flat, hazy, featureless clouds of low altitude varying in color...
s.
Altostratus clouds are formed by the rising of a large air mass
Air mass
In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. They are classified according to latitude and their continental or maritime...
that condenses into a cloud. They can produce light precipitation, often in the form of virga
Virga
In meteorology, virga is an observable streak or shaft of precipitation that falls from a cloud but evaporates before reaching the ground. At high altitudes the precipitation falls mainly as ice crystals before melting and finally evaporating; this is usually due to compressional heating, because...
. If the precipitation increases in persistence and intensity, the altostratus cloud may thicken into nimbostratus.
Altostratus most often takes the form of a featureless sheet of cloud but can be wavy (undulatus) as a result of wind shear through the cloud. It can also be fragmented (fibratus) with clear sky visible, which often signals the approach of a weakened warm front.
Description
Altostratus clouds may be composed of either water droplets or ice crystals. In some ice crystal altostratus, very thin, rapidly-disappearing horizontal sheets of water droplets appear at random. The sizes of the ice crystals in the cloud tended to increase as altitude decreased. However, close to the bottom of the cloud, the particles decreased in size again. During the sampling of one cloud, the scientists noted a haloHalo (optical phenomenon)
A halo from Greek ἅλως; also known as a nimbus, icebow or gloriole) is an optical phenomenon produced by ice crystals creating colored or white arcs and spots in the sky. Many are near the sun or moon but others are elsewhere and even in the opposite part of the sky...
while flying near the top of the cloud, which indicated that the ice crystals were hexagonal near the top. However, farther down, the ice crystals became more conglomerated
Conglomerate (geology)
A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts...
.
Formation
Altostratus is caused by a large air massAir mass
In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. They are classified according to latitude and their continental or maritime...
that is lifted then condensed
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
, usually by an incoming frontal system, and they can be found over widespread areas. Their altitude is from 6,500–20,000 feet (2,400–6,100 meters). They are primarily composed of water droplets. They can rise at velocities up to .05 to .1 meters per second (.16 to .33 feet per second). They can also be the result of the thickening of a cirrostratus cloud
Cirrostratus cloud
Cirrostratus clouds are thin, generally uniform clouds, composed of ice-crystals. They are difficult to detect and if capable of forming halos the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no haloes if it is thicker cirrostratus fibratus. On the...
. Altostratus is rarely seen alone in the sky, as there is usually some accompanying stratocumulus or stratus fractus underneath it, this being due to the increased moisture beneath the altostratus or cumulus clouds dying as the altostratus dims heat from the sun.
External links
- Clouds-Online.com Cloud Atlas with many photos and description of the different cloud genus
- National Science Digital Library - Altostratus
Gallery
Altostratus is a cloudCloud
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...
belonging to a class characterized by a generally uniform gray to bluish-gray sheet or layer, lighter in color than nimbostratus
Nimbostratus cloud
A Nimbostratus cloud is characterized by a formless cloud layer that is almost uniformly dark gray. "Nimbo" is from the Latin word "nimbus", which denotes precipitation. It is generally a stratiform cloud of moderate vertical development that produces precipitation, developing cloud bases between...
and darker than cirrostratus
Cirrostratus cloud
Cirrostratus clouds are thin, generally uniform clouds, composed of ice-crystals. They are difficult to detect and if capable of forming halos the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no haloes if it is thicker cirrostratus fibratus. On the...
. The sun can be seen through thin altostratus, but thicker layers can be quite opaque. They can look similar to lower altitude stratus cloud
Stratus cloud
A stratus cloud is a cloud belonging to a class characterized by horizontal layering with a uniform base, as opposed to convective clouds that are as tall or taller than wide . More specifically, the term stratus is used to describe flat, hazy, featureless clouds of low altitude varying in color...
s.
Altostratus clouds are formed by the rising of a large air mass
Air mass
In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. They are classified according to latitude and their continental or maritime...
that condenses into a cloud. They can produce light precipitation, often in the form of virga
Virga
In meteorology, virga is an observable streak or shaft of precipitation that falls from a cloud but evaporates before reaching the ground. At high altitudes the precipitation falls mainly as ice crystals before melting and finally evaporating; this is usually due to compressional heating, because...
. If the precipitation increases in persistence and intensity, the altostratus cloud may thicken into nimbostratus.
Altostratus most often takes the form of a featureless sheet of cloud but can be wavy (undulatus) as a result of wind shear through the cloud. It can also be fragmented (fibratus) with clear sky visible, which often signals the approach of a weakened warm front.
Description
Altostratus clouds may be composed of either water droplets or ice crystals. In some ice crystal altostratus, very thin, rapidly-disappearing horizontal sheets of water droplets appear at random. The sizes of the ice crystals in the cloud tended to increase as altitude decreased. However, close to the bottom of the cloud, the particles decreased in size again. During the sampling of one cloud, the scientists noted a haloHalo (optical phenomenon)
A halo from Greek ἅλως; also known as a nimbus, icebow or gloriole) is an optical phenomenon produced by ice crystals creating colored or white arcs and spots in the sky. Many are near the sun or moon but others are elsewhere and even in the opposite part of the sky...
while flying near the top of the cloud, which indicated that the ice crystals were hexagonal near the top. However, farther down, the ice crystals became more conglomerated
Conglomerate (geology)
A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts...
.
Formation
Altostratus is caused by a large air massAir mass
In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. They are classified according to latitude and their continental or maritime...
that is lifted then condensed
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
, usually by an incoming frontal system, and they can be found over widespread areas. Their altitude is from 6,500–20,000 feet (2,400–6,100 meters). They are primarily composed of water droplets. They can rise at velocities up to .05 to .1 meters per second (.16 to .33 feet per second). They can also be the result of the thickening of a cirrostratus cloud
Cirrostratus cloud
Cirrostratus clouds are thin, generally uniform clouds, composed of ice-crystals. They are difficult to detect and if capable of forming halos the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no haloes if it is thicker cirrostratus fibratus. On the...
. Altostratus is rarely seen alone in the sky, as there is usually some accompanying stratocumulus or stratus fractus underneath it, this being due to the increased moisture beneath the altostratus or cumulus clouds dying as the altostratus dims heat from the sun.
External links
- Clouds-Online.com Cloud Atlas with many photos and description of the different cloud genus
- National Science Digital Library - Altostratus
Gallery
Altostratus is a cloudCloud
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...
belonging to a class characterized by a generally uniform gray to bluish-gray sheet or layer, lighter in color than nimbostratus
Nimbostratus cloud
A Nimbostratus cloud is characterized by a formless cloud layer that is almost uniformly dark gray. "Nimbo" is from the Latin word "nimbus", which denotes precipitation. It is generally a stratiform cloud of moderate vertical development that produces precipitation, developing cloud bases between...
and darker than cirrostratus
Cirrostratus cloud
Cirrostratus clouds are thin, generally uniform clouds, composed of ice-crystals. They are difficult to detect and if capable of forming halos the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no haloes if it is thicker cirrostratus fibratus. On the...
. The sun can be seen through thin altostratus, but thicker layers can be quite opaque. They can look similar to lower altitude stratus cloud
Stratus cloud
A stratus cloud is a cloud belonging to a class characterized by horizontal layering with a uniform base, as opposed to convective clouds that are as tall or taller than wide . More specifically, the term stratus is used to describe flat, hazy, featureless clouds of low altitude varying in color...
s.
Altostratus clouds are formed by the rising of a large air mass
Air mass
In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. They are classified according to latitude and their continental or maritime...
that condenses into a cloud. They can produce light precipitation, often in the form of virga
Virga
In meteorology, virga is an observable streak or shaft of precipitation that falls from a cloud but evaporates before reaching the ground. At high altitudes the precipitation falls mainly as ice crystals before melting and finally evaporating; this is usually due to compressional heating, because...
. If the precipitation increases in persistence and intensity, the altostratus cloud may thicken into nimbostratus.
Altostratus most often takes the form of a featureless sheet of cloud but can be wavy (undulatus) as a result of wind shear through the cloud. It can also be fragmented (fibratus) with clear sky visible, which often signals the approach of a weakened warm front.
Description
Altostratus clouds may be composed of either water droplets or ice crystals. In some ice crystal altostratus, very thin, rapidly-disappearing horizontal sheets of water droplets appear at random. The sizes of the ice crystals in the cloud tended to increase as altitude decreased. However, close to the bottom of the cloud, the particles decreased in size again. During the sampling of one cloud, the scientists noted a haloHalo (optical phenomenon)
A halo from Greek ἅλως; also known as a nimbus, icebow or gloriole) is an optical phenomenon produced by ice crystals creating colored or white arcs and spots in the sky. Many are near the sun or moon but others are elsewhere and even in the opposite part of the sky...
while flying near the top of the cloud, which indicated that the ice crystals were hexagonal near the top. However, farther down, the ice crystals became more conglomerated
Conglomerate (geology)
A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts...
.
Formation
Altostratus is caused by a large air massAir mass
In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. They are classified according to latitude and their continental or maritime...
that is lifted then condensed
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
, usually by an incoming frontal system, and they can be found over widespread areas. Their altitude is from 6,500–20,000 feet (2,400–6,100 meters). They are primarily composed of water droplets. They can rise at velocities up to .05 to .1 meters per second (.16 to .33 feet per second). They can also be the result of the thickening of a cirrostratus cloud
Cirrostratus cloud
Cirrostratus clouds are thin, generally uniform clouds, composed of ice-crystals. They are difficult to detect and if capable of forming halos the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no haloes if it is thicker cirrostratus fibratus. On the...
. Altostratus is rarely seen alone in the sky, as there is usually some accompanying stratocumulus or stratus fractus underneath it, this being due to the increased moisture beneath the altostratus or cumulus clouds dying as the altostratus dims heat from the sun.
External links
- Clouds-Online.com Cloud Atlas with many photos and description of the different cloud genus
- National Science Digital Library - Altostratus
Gallery
Altostratus is a cloudCloud
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...
belonging to a class characterized by a generally uniform gray to bluish-gray sheet or layer, lighter in color than nimbostratus
Nimbostratus cloud
A Nimbostratus cloud is characterized by a formless cloud layer that is almost uniformly dark gray. "Nimbo" is from the Latin word "nimbus", which denotes precipitation. It is generally a stratiform cloud of moderate vertical development that produces precipitation, developing cloud bases between...
and darker than cirrostratus
Cirrostratus cloud
Cirrostratus clouds are thin, generally uniform clouds, composed of ice-crystals. They are difficult to detect and if capable of forming halos the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no haloes if it is thicker cirrostratus fibratus. On the...
. The sun can be seen through thin altostratus, but thicker layers can be quite opaque. They can look similar to lower altitude stratus cloud
Stratus cloud
A stratus cloud is a cloud belonging to a class characterized by horizontal layering with a uniform base, as opposed to convective clouds that are as tall or taller than wide . More specifically, the term stratus is used to describe flat, hazy, featureless clouds of low altitude varying in color...
s.
Altostratus clouds are formed by the rising of a large air mass
Air mass
In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. They are classified according to latitude and their continental or maritime...
that condenses into a cloud. They can produce light precipitation, often in the form of virga
Virga
In meteorology, virga is an observable streak or shaft of precipitation that falls from a cloud but evaporates before reaching the ground. At high altitudes the precipitation falls mainly as ice crystals before melting and finally evaporating; this is usually due to compressional heating, because...
. If the precipitation increases in persistence and intensity, the altostratus cloud may thicken into nimbostratus.
Altostratus most often takes the form of a featureless sheet of cloud but can be wavy (undulatus) as a result of wind shear through the cloud. It can also be fragmented (fibratus) with clear sky visible, which often signals the approach of a weakened warm front.
Description
Altostratus clouds may be composed of either water droplets or ice crystals. In some ice crystal altostratus, very thin, rapidly-disappearing horizontal sheets of water droplets appear at random. The sizes of the ice crystals in the cloud tended to increase as altitude decreased. However, close to the bottom of the cloud, the particles decreased in size again. During the sampling of one cloud, the scientists noted a haloHalo (optical phenomenon)
A halo from Greek ἅλως; also known as a nimbus, icebow or gloriole) is an optical phenomenon produced by ice crystals creating colored or white arcs and spots in the sky. Many are near the sun or moon but others are elsewhere and even in the opposite part of the sky...
while flying near the top of the cloud, which indicated that the ice crystals were hexagonal near the top. However, farther down, the ice crystals became more conglomerated
Conglomerate (geology)
A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts...
.
Formation
Altostratus is caused by a large air massAir mass
In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. They are classified according to latitude and their continental or maritime...
that is lifted then condensed
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
, usually by an incoming frontal system, and they can be found over widespread areas. Their altitude is from 6,500–20,000 feet (2,400–6,100 meters). They are primarily composed of water droplets. They can rise at velocities up to .05 to .1 meters per second (.16 to .33 feet per second). They can also be the result of the thickening of a cirrostratus cloud
Cirrostratus cloud
Cirrostratus clouds are thin, generally uniform clouds, composed of ice-crystals. They are difficult to detect and if capable of forming halos the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no haloes if it is thicker cirrostratus fibratus. On the...
. Altostratus is rarely seen alone in the sky, as there is usually some accompanying stratocumulus or stratus fractus underneath it, this being due to the increased moisture beneath the altostratus or cumulus clouds dying as the altostratus dims heat from the sun.
External links
- Clouds-Online.com Cloud Atlas with many photos and description of the different cloud genus
- National Science Digital Library - Altostratus
Gallery
Altostratus is a cloudCloud
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...
belonging to a class characterized by a generally uniform gray to bluish-gray sheet or layer, lighter in color than nimbostratus
Nimbostratus cloud
A Nimbostratus cloud is characterized by a formless cloud layer that is almost uniformly dark gray. "Nimbo" is from the Latin word "nimbus", which denotes precipitation. It is generally a stratiform cloud of moderate vertical development that produces precipitation, developing cloud bases between...
and darker than cirrostratus
Cirrostratus cloud
Cirrostratus clouds are thin, generally uniform clouds, composed of ice-crystals. They are difficult to detect and if capable of forming halos the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no haloes if it is thicker cirrostratus fibratus. On the...
. The sun can be seen through thin altostratus, but thicker layers can be quite opaque. They can look similar to lower altitude stratus cloud
Stratus cloud
A stratus cloud is a cloud belonging to a class characterized by horizontal layering with a uniform base, as opposed to convective clouds that are as tall or taller than wide . More specifically, the term stratus is used to describe flat, hazy, featureless clouds of low altitude varying in color...
s.
Altostratus clouds are formed by the rising of a large air mass
Air mass
In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. They are classified according to latitude and their continental or maritime...
that condenses into a cloud. They can produce light precipitation, often in the form of virga
Virga
In meteorology, virga is an observable streak or shaft of precipitation that falls from a cloud but evaporates before reaching the ground. At high altitudes the precipitation falls mainly as ice crystals before melting and finally evaporating; this is usually due to compressional heating, because...
. If the precipitation increases in persistence and intensity, the altostratus cloud may thicken into nimbostratus.
Altostratus most often takes the form of a featureless sheet of cloud but can be wavy (undulatus) as a result of wind shear through the cloud. It can also be fragmented (fibratus) with clear sky visible, which often signals the approach of a weakened warm front.
Description
Altostratus clouds may be composed of either water droplets or ice crystals. In some ice crystal altostratus, very thin, rapidly-disappearing horizontal sheets of water droplets appear at random. The sizes of the ice crystals in the cloud tended to increase as altitude decreased. However, close to the bottom of the cloud, the particles decreased in size again. During the sampling of one cloud, the scientists noted a haloHalo (optical phenomenon)
A halo from Greek ἅλως; also known as a nimbus, icebow or gloriole) is an optical phenomenon produced by ice crystals creating colored or white arcs and spots in the sky. Many are near the sun or moon but others are elsewhere and even in the opposite part of the sky...
while flying near the top of the cloud, which indicated that the ice crystals were hexagonal near the top. However, farther down, the ice crystals became more conglomerated
Conglomerate (geology)
A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts...
.
Formation
Altostratus is caused by a large air massAir mass
In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. They are classified according to latitude and their continental or maritime...
that is lifted then condensed
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
, usually by an incoming frontal system, and they can be found over widespread areas. Their altitude is from 6,500–20,000 feet (2,400–6,100 meters). They are primarily composed of water droplets. They can rise at velocities up to .05 to .1 meters per second (.16 to .33 feet per second). They can also be the result of the thickening of a cirrostratus cloud
Cirrostratus cloud
Cirrostratus clouds are thin, generally uniform clouds, composed of ice-crystals. They are difficult to detect and if capable of forming halos the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no haloes if it is thicker cirrostratus fibratus. On the...
. Altostratus is rarely seen alone in the sky, as there is usually some accompanying stratocumulus or stratus fractus underneath it, this being due to the increased moisture beneath the altostratus or cumulus clouds dying as the altostratus dims heat from the sun.
External links
- Clouds-Online.com Cloud Atlas with many photos and description of the different cloud genus
- National Science Digital Library - Altostratus
Gallery
Altostratus is a cloudCloud
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...
belonging to a class characterized by a generally uniform gray to bluish-gray sheet or layer, lighter in color than nimbostratus
Nimbostratus cloud
A Nimbostratus cloud is characterized by a formless cloud layer that is almost uniformly dark gray. "Nimbo" is from the Latin word "nimbus", which denotes precipitation. It is generally a stratiform cloud of moderate vertical development that produces precipitation, developing cloud bases between...
and darker than cirrostratus
Cirrostratus cloud
Cirrostratus clouds are thin, generally uniform clouds, composed of ice-crystals. They are difficult to detect and if capable of forming halos the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no haloes if it is thicker cirrostratus fibratus. On the...
. The sun can be seen through thin altostratus, but thicker layers can be quite opaque. They can look similar to lower altitude stratus cloud
Stratus cloud
A stratus cloud is a cloud belonging to a class characterized by horizontal layering with a uniform base, as opposed to convective clouds that are as tall or taller than wide . More specifically, the term stratus is used to describe flat, hazy, featureless clouds of low altitude varying in color...
s.
Altostratus clouds are formed by the rising of a large air mass
Air mass
In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. They are classified according to latitude and their continental or maritime...
that condenses into a cloud. They can produce light precipitation, often in the form of virga
Virga
In meteorology, virga is an observable streak or shaft of precipitation that falls from a cloud but evaporates before reaching the ground. At high altitudes the precipitation falls mainly as ice crystals before melting and finally evaporating; this is usually due to compressional heating, because...
. If the precipitation increases in persistence and intensity, the altostratus cloud may thicken into nimbostratus.
Altostratus most often takes the form of a featureless sheet of cloud but can be wavy (undulatus) as a result of wind shear through the cloud. It can also be fragmented (fibratus) with clear sky visible, which often signals the approach of a weakened warm front.
Description
Altostratus clouds may be composed of either water droplets or ice crystals. In some ice crystal altostratus, very thin, rapidly-disappearing horizontal sheets of water droplets appear at random. The sizes of the ice crystals in the cloud tended to increase as altitude decreased. However, close to the bottom of the cloud, the particles decreased in size again. During the sampling of one cloud, the scientists noted a haloHalo (optical phenomenon)
A halo from Greek ἅλως; also known as a nimbus, icebow or gloriole) is an optical phenomenon produced by ice crystals creating colored or white arcs and spots in the sky. Many are near the sun or moon but others are elsewhere and even in the opposite part of the sky...
while flying near the top of the cloud, which indicated that the ice crystals were hexagonal near the top. However, farther down, the ice crystals became more conglomerated
Conglomerate (geology)
A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts...
.
Formation
Altostratus is caused by a large air massAir mass
In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. They are classified according to latitude and their continental or maritime...
that is lifted then condensed
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
, usually by an incoming frontal system, and they can be found over widespread areas. Their altitude is from 6,500–20,000 feet (2,400–6,100 meters). They are primarily composed of water droplets. They can rise at velocities up to .05 to .1 meters per second (.16 to .33 feet per second). They can also be the result of the thickening of a cirrostratus cloud
Cirrostratus cloud
Cirrostratus clouds are thin, generally uniform clouds, composed of ice-crystals. They are difficult to detect and if capable of forming halos the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no haloes if it is thicker cirrostratus fibratus. On the...
. Altostratus is rarely seen alone in the sky, as there is usually some accompanying stratocumulus or stratus fractus underneath it, this being due to the increased moisture beneath the altostratus or cumulus clouds dying as the altostratus dims heat from the sun.
External links
- Clouds-Online.com Cloud Atlas with many photos and description of the different cloud genus
- National Science Digital Library - Altostratus
Gallery
Altostratus is a cloudCloud
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...
belonging to a class characterized by a generally uniform gray to bluish-gray sheet or layer, lighter in color than nimbostratus
Nimbostratus cloud
A Nimbostratus cloud is characterized by a formless cloud layer that is almost uniformly dark gray. "Nimbo" is from the Latin word "nimbus", which denotes precipitation. It is generally a stratiform cloud of moderate vertical development that produces precipitation, developing cloud bases between...
and darker than cirrostratus
Cirrostratus cloud
Cirrostratus clouds are thin, generally uniform clouds, composed of ice-crystals. They are difficult to detect and if capable of forming halos the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no haloes if it is thicker cirrostratus fibratus. On the...
. The sun can be seen through thin altostratus, but thicker layers can be quite opaque. They can look similar to lower altitude stratus cloud
Stratus cloud
A stratus cloud is a cloud belonging to a class characterized by horizontal layering with a uniform base, as opposed to convective clouds that are as tall or taller than wide . More specifically, the term stratus is used to describe flat, hazy, featureless clouds of low altitude varying in color...
s.
Altostratus clouds are formed by the rising of a large air mass
Air mass
In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. They are classified according to latitude and their continental or maritime...
that condenses into a cloud. They can produce light precipitation, often in the form of virga
Virga
In meteorology, virga is an observable streak or shaft of precipitation that falls from a cloud but evaporates before reaching the ground. At high altitudes the precipitation falls mainly as ice crystals before melting and finally evaporating; this is usually due to compressional heating, because...
. If the precipitation increases in persistence and intensity, the altostratus cloud may thicken into nimbostratus.
Altostratus most often takes the form of a featureless sheet of cloud but can be wavy (undulatus) as a result of wind shear through the cloud. It can also be fragmented (fibratus) with clear sky visible, which often signals the approach of a weakened warm front.
Description
Altostratus clouds may be composed of either water droplets or ice crystals. In some ice crystal altostratus, very thin, rapidly-disappearing horizontal sheets of water droplets appear at random. The sizes of the ice crystals in the cloud tended to increase as altitude decreased. However, close to the bottom of the cloud, the particles decreased in size again. During the sampling of one cloud, the scientists noted a haloHalo (optical phenomenon)
A halo from Greek ἅλως; also known as a nimbus, icebow or gloriole) is an optical phenomenon produced by ice crystals creating colored or white arcs and spots in the sky. Many are near the sun or moon but others are elsewhere and even in the opposite part of the sky...
while flying near the top of the cloud, which indicated that the ice crystals were hexagonal near the top. However, farther down, the ice crystals became more conglomerated
Conglomerate (geology)
A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts...
.
Formation
Altostratus is caused by a large air massAir mass
In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. They are classified according to latitude and their continental or maritime...
that is lifted then condensed
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
, usually by an incoming frontal system, and they can be found over widespread areas. Their altitude is from 6,500–20,000 feet (2,400–6,100 meters). They are primarily composed of water droplets. They can rise at velocities up to .05 to .1 meters per second (.16 to .33 feet per second). They can also be the result of the thickening of a cirrostratus cloud
Cirrostratus cloud
Cirrostratus clouds are thin, generally uniform clouds, composed of ice-crystals. They are difficult to detect and if capable of forming halos the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no haloes if it is thicker cirrostratus fibratus. On the...
. Altostratus is rarely seen alone in the sky, as there is usually some accompanying stratocumulus or stratus fractus underneath it, this being due to the increased moisture beneath the altostratus or cumulus clouds dying as the altostratus dims heat from the sun.
External links
- Clouds-Online.com Cloud Atlas with many photos and description of the different cloud genus
- National Science Digital Library - Altostratus
Gallery
Image:Altostratus undulatus at sunrise.jpg|Altostratus undulatus at sunrise
Image:Unusually well defined warm front.jpg|Altostratus opacus at the edge of a warm front
Image:As 1.jpg|Altostratus translucidus with stratocumulus below
Image:Altostratus.jpg|Altostratus translucidus