10 Spectacular Cloud Formations! |
Clouds have always fascinating us.
When we picture heaven, clouds usually make an appearance of some kind.
They are the mystreious figures that are always hovering above us,
showeing us with water, and floating as if by magic. Clouds are our
almsot constant companions, and yet, most of us know very little about
our up top neighbors. So here is your chance to learn about 10
incredible cloud formations:
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1. Lenticular Clouds
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Lenticular clouds (Altocumulus
lenticularis) are stationary lens-shaped clouds that form at high
altitudes, normally aligned perpendicular to the wind direction.
Lenticular clouds can be separated into altocumulus standing
lenticularis (ACSL), stratocumulus standing lenticular (SCSL), and
cirrocumulus standing lenticular (CCSL). Due to their shape, they have
been offered as an explanation for some Unidentified Flying Object (UFO)
sightings.
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Where stable moist air flows over a
mountain or a range of mountains, a series of large-scale standing waves
may form on the downwind side. If the temperature at the crest of the
wave drops to the dew point, moisture in the air may condense to form
lenticular clouds. As the moist air moves back down into the trough of
the wave, the cloud may evaporate back into vapor.
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2. Wave Clouds |
A wave cloud is a cloud form created
by atmospheric internal waves. The atmospheric internal waves that form
wave clouds are created as stable air flows over a raised land feature
such as a mountain range, and can form either directly above or in the
lee of the feature. As an air mass travels through the wave, it
undergoes repeated uplift and descent. If there is enough moisture in
the atmosphere, clouds will form at the cooled crests of these waves. In
the descending part of the wave, those clouds will evaporate due to
adiabatic heating, leading to the characteristic clouded and clear
bands. The cloud base on the leeward side is higher than on the windward
side, because precipitation on the windward side removes water from the
air.
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It is possible that simple convection
from mountain summits can also form wave clouds. This occurs as the
convection forces a wave or lenticular wave cloud into the more stable
air above.
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3. Noctilucent (night) clouds
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Night clouds or noctilucent clouds
are tenuous cloud-like phenomena that are the “ragged-edge” of a much
brighter and pervasive polar cloud layer called polar mesospheric clouds
in the upper atmosphere, visible in a deep twilight. They are made of
crystals of water ice. The name means roughly night shining in Latin.
They are most commonly observed in the summer months at latitudes
between 50° and 70° north and south of the equator.
They are the highest clouds in the
Earth’s atmosphere, located in the mesosphere at altitudes of around 76
to 85 kilometres (47 to 53 mi). They are normally too faint to be seen,
and are visible only when illuminated by sunlight from below the horizon
while the lower layers of the atmosphere are in the Earth’s shadow.
Noctilucent clouds are not fully understood and are a recently
discovered meteorological phenomenon; there is no record of their
observation before 1885.
Noctilucent clouds can form only
under very restrictive conditions; their occurrence can be used as a
sensitive guide to changes in the upper atmosphere. Since they are a
relatively recent classification, the occurrence of noctilucent clouds
appears to be increasing in frequency, brightness and extent. It is
theorized that this increase is connected to climate change.
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4. Morning Glory Clouds |
The Morning Glory cloud is a rare
meteorological phenomenon occasionally observed in different locations
around the world. The southern part of Northern Australia’s Gulf of
Carpentaria is the only known location where it can be predicted and
observed on a more or less regular basis. The settlement of Burketown
attracts glider pilots intent on riding this phenomenon.
Morning Glory clouds can most often
be observed in Burketown in September to mid-November, when the chance
to see it early in the morning is approximately 40%. A Morning Glory
cloud is a roll cloud that can be up to 1,000 kilometres (620 mi) long, 1
to 2 kilometres (0.62 to 1.2 mi) high, often only 100 to 200 metres
(330 to 660 ft) above the ground and can move at speeds up to 60
kilometres (37 mi) per hour. Sometimes there is only one cloud,
sometimes there are up to eight consecutive roll clouds.
The Morning Glory is often
accompanied by sudden wind squalls, intense low-level wind shear, a
rapid increase in the vertical displacement of air parcels, and a sharp
pressure jump at the surface. In the front of the cloud, there is strong
vertical motion that transports air up through the cloud and creates
the rolling appearance, while the air in the middle and rear of the
cloud becomes turbulent and sinks. The cloud can also be described as a
solitary wave or a soliton, which is a wave that has a single crest and
moves without changing speed or shape.
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5. Pyrocumuls Cloud |
A pyrocumulus, or fire cloud, is a
dense cumuliform cloud associated with fire or volcanic activity. A
pyrocumulus is similar dynamically in some ways to a firestorm, and the
two phenomena may occur in conjunction with each other. However, one may
occur without the other. A pyrocumulus cloud is produced by the intense
heating of the air from the surface.
The intense heat induces convection
which causes the air mass to rise to a point of stability, usually in
the presence of moisture. Phenomena such as volcanic eruptions, forest
fires, and occasionally industrial activities can induce formation of
this cloud. The detonation of a nuclear weapon in the atmosphere will
also produce a pyrocumulus in the form of a mushroom cloud which is made
by the same mechanism. The presence of a low level jet stream can
enhance its formation. Condensation of ambient moisture (moisture
already present in the atmosphere) as well as moisture evaporated from
burnt vegetation or volcanic outgassing occurs readily on particles of
ash.
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6. Wave windows |
In meteorology, lee waves are
atmospheric standing waves. Both lee waves and the rotor may be
indicated by specific wave cloud formations if there is sufficient
moisture in the atmosphere, and sufficient vertical displacement to cool
the air to the dew point. Waves may also form in dry air without cloud
markers. Wave clouds do not move downwind as clouds usually do, but
remain fixed in position relative to the obstruction that forms them.
Adiabatic compression heating in the
trough of each wave oscillation may evaporate cumulus or stratus clouds
in the airmass, creating a “wave window” or “Foehn gap”.
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7. Undulatus asperatus |
Undulatus asperatus (or alternately,
asperatus) is a cloud formation, proposed in 2009 as a separate cloud
classification by the founder of the Cloud Appreciation Society. If
successful it will be the first cloud formation added since cirrus
intortus in 1951 to the International Cloud Atlas of the World
Meteorological Organization. The name translates approximately as
roughened or agitated waves
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The clouds are most closely related
to undulatus clouds. Although they appear dark and storm-like, they tend
to dissipate without a storm forming. The ominous-looking clouds have
been particularly common in the Plains states of the United States,
often during the morning or midday hours following convective
thunderstorm activity.
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8. Fallstreak Hole or Hole Punch Cloud |
A fallstreak hole, also known as a
hole punch cloud, punch hole cloud, canal cloud or cloud hole, is a
large circular gap that can appear in cirrocumulus or altocumulus
clouds. Such holes are formed when the water temperature in the clouds
is below freezing but the water has not frozen yet due to the lack of
ice nucleation particles.
When a portion of the water does
start to freeze it will set off a domino effect, due to the Bergeron
process, causing the water vapor around it to freeze and fall to the
earth as well. This leaves a large, often circular, hole in the cloud.
It is believed that a disruption in the stability of the cloud layer,
such as that caused by a passing jet, may induce the domino process of
evaporation which creates the hole. Such clouds are not unique to any
one geographic area and have been photographed from the United States to
Russia. Because of their rarity and unusual appearance, fallstreak
holes are often mistaken for or attributed to unidentified flying
objects.
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9. Mamatus Clouds |
Mammatus, 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. The name mammatus, derived from the
Latin mamma (meaning “udder” or “breast”), refers to a resemblance
between the characteristic shape of these clouds and the breast of a
woman.
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Mammatus are most often associated
with the anvil cloud and also severe thunderstorms. They often extend
from the base of a cumulonimbus, but may also be found under
altocumulus, altostratus, stratocumulus, and cirrus clouds, as well as
volcanic ash clouds.Mammatus are most often associated with the anvil
cloud and also severe thunderstorms. They often extend from the base of a
cumulonimbus, but may also be found under altocumulus, altostratus,
stratocumulus, and cirrus clouds, as well as volcanic ash clouds. |
10. Cloud iridescence |
Cloud iridescence is the occurrence
of colors in a cloud similar to those seen in oil films on puddles, and
is similar to irisation. It is a fairly uncommon phenomenon, most often
observed in altocumulus, cirrocumulus and lenticular clouds, and very
rarely in Cirrus clouds. The colors are usually pastel, but can be very
vivid. Iridescence is generally produced near the sun, with the sun’s
glare masking it, so it is more easily seen by hiding the sun behind a
tree or building. Other aids are dark glasses, or observing the sky
reflected in a convex mirror or in a pool of water.
Iridescent clouds are a diffraction
phenomenon cause by small water droplets or small ice crystals
individually scattering light. Larger ice crystals produce halos, which
are a refraction phenomena rather than iridescence. Iridescence should
similarly be distinguished from the refraction in larger raindrops that
makes a rainbow.
If parts of clouds have small
droplets or crystals of similar size, their cumulative effect is seen as
colors. The cloud must be optically thin, so that most rays encounter
only a single droplet. Iridescence is therefore mostly seen at cloud
edges or in semi-transparent clouds, and newly forming clouds produce
the brightest and most colorful iridescence.
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dimanche 12 octobre 2014
10 Spectacular Cloud Formations!
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