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Cirrocumulus
clouds
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Look Like rippled sand. An omen
of fair weather, they usually follow a storm and
dissipate to leave a clear blue sky. 5-8 km
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Altocumulus
clouds
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Fair-weather clouds, on a larger
scale than cirrocumulus, thicker, not so white and
with shadows in them. Usually appear after a
storm, drifting at 1.5-6 km
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Cumulonimbus
clouds
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Low thunder clouds. Dark and
menacing, with the top flattering out in an anvil
shape. Bring hail, a strong wind, thunder and
lightning. False cirrus appear above them, false
nimbustratus below. 1.5-10 km
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Cumulus
Clouds
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Easily
recognisable: fluffy white clouds. Usually
indicates fair weather when widely separated, but
if large and many-headed, they are capable of
producing sudden heavy showers. When seen at sea
is an otherwise cloudless sky, they are often an
indication of land beneath. 2.5 km and less.
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Cirrus
Clouds
High,
wispy clouds formed from ice crystals which them a
white appearance. Seen in fine weather. 5-9km
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Cloud,
condensed form of atmospheric moisture consisting of small
water droplets or tiny ice crystals.
Clouds are the principal visible phenomena of the
atmosphere. They represent a transitory but vital step in
the water cycle, which includes evaporation of moisture
from the surface of the earth, carrying of this moisture
into higher levels of the atmosphere, condensation of
water vapor into cloud masses, and final return of water
to the surface as precipitation.
The
formation of clouds caused by cooling of the air results
in the condensation of invisible water vapor that produces
visible cloud droplets or ice particles.
Cloud
particles range in size from about 5 to 75 micrometers
(0.0005 to 0.008 cm/0.0002 to 0.003 in). The particles are
so small that light, vertical currents easily sustain them
in the air. The different cloud formations result partly
from the temperature at which condensation takes place.
When condensation occurs at temperatures below freezing,
clouds are usually composed of ice crystals; those that
form in warmer air usually consist of water droplets.
Occasionally, however, supercooled clouds contain water
droplets at subfreezing temperatures. The air motion
associated with cloud development also affects formation.
Clouds that develop in calm air tend to appear as sheets
or stratified formations; those that form under windy
conditions or in air with strong vertical currents have a
towering appearance.
Clouds
perform a very important function in modifying the
distribution of solar heat over the earth's surface and
within the atmosphere. In general, because reflection from
the tops of clouds is greater than reflection from the
surface of the earth, the amount of solar energy reflected
back to space is greater on cloudy days. Although most
solar radiation is reflected back by the upper layers of
the clouds, some radiation penetrates to the surface of
the earth, which absorbs this energy and reradiates it.
The lower parts of clouds are opaque to this long-wave
earth radiation and reflect it back toward earth. The
result is that the lower atmosphere generally absorbs more
radiative heat energy on a cloudy day because of the
presence of this trapped radiation. By contrast, on a
clear day more solar radiation is initially absorbed by
the surface of the earth, but when reradiated this energy
is quickly dissipated because of the absence of clouds.
Disregarding related meteorological elements, the
atmosphere actually absorbs less radiation on clear days
than on cloudy days.
Cloudiness
has considerable influence on human activities. Rainfall,
which is very important for agricultural activities, has
its genesis in the formation of clouds. The marked effect
of clouds on visibility at flight levels proved to be a
major difficulty during the early days of the airplane, a
hazard that was alleviated with the development of
instrument flying, which permits the pilot to navigate
even in the midst of a thick cloud. The sharp increase in
consumption of electricity for lighting during cloudy days
represents one of the major scheduling problems faced by
the electric-power industry.
this
information has brought it to you from Encarta 2002
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Cirrostratus
Clouds
Made
up of ice particles and look like white veins.
These produce a halo round the Sun or Moon. If a
cirrus-filled sky darkens and the clouds change to
cirrostratus it is an indication that rain or snow
is on the way. 5-9km
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Altostratus
Clouds
Form
greyish veil over the sun or moon. If wet weather
is approaching the cloud will darken and thicken,
obscuring the sun and moon until it begin to rain.
2.5-6km
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Nimbostratus
Clouds
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Form
low, dark blankets, which signals rain or snow
within 4-5 hours, usually lasting several hours. 1.5-5km
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Stratocumulus
Clouds
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Form
a low, lumpy, rolling mass, usually covering the
whole sky, though often thin enough for the sun to
filter through. Light showers may precipitate from
them, but these clouds usually dissipate in the
afternoon, leaving a clear night sky. Below
2.5km
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Stratus
Clouds
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These
are the lowest of clouds and form a uniform layer
like fog in the air – they are often described
as hill fog. Although not a normal rain cloud,
they can produce drizzle. When they form thickly
overnight and cover the morning sky they will
usually be followed by a fine day. Less
than 2.5km
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