What are clouds and how do they form? - Met Office

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** What are clouds and how do they form? **

Clouds are made of tiny drops of water or ice crystals that settle on dust
particles in the atmosphere. The droplets are so small - a diameter of
about a hundredth of a millimetre - that each cubic metre of air will
contain 100 million droplets.

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How do clouds form

*Related articles*

· Cloud spotting guide
· High clouds
· Low-level clouds
· Mid-level clouds
· Other clouds
· Cloud names and classifications

*Related media*

· Clouds fact sheet (PDF, 12 MB)

Clouds will either be composed of ice or water droplets depending on the
height of the cloud and the temperature of the atmosphere. Because the
droplets are so small, they can remain in liquid form in temperatures as
low as -30 °C. Extremely high clouds at temperatures below -30 °C are
composed of ice crystals.

*How do clouds form?*

Clouds form when the invisible water vapour in the air condenses into
visible water droplets or ice crystals. There is water around us all the
time in the form of tiny gas particles, also known as water vapour. There
are also tiny particles floating around in the air - such as salt and dust

Source: www.metoffice.gov.uk/learning/clouds/what-are-clouds

how are clouds formed

Cloud - Wikipedia, the free encyclopedia


** Cloud **

From Wikipedia, the free encyclopedia
Jump to: navigation, search
For other uses, see Cloud (disambiguation).
Stratocumulus stratiformis cumulogenitus

In meteorology, a *cloud* is a visible mass of liquid droplets or frozen
crystals made of water or various chemicals suspended in the atmosphere
above the surface of a planetary body.^[1] These suspended particles are
also known as aerosols. Clouds in Earth's atmosphere are studied in the
cloud physics branch of meteorology. Two processes, possibly acting
together, can lead to air becoming saturated; cooling the air or adding
water vapor to the air. In general, precipitation will fall to the surface;
an exception is virga, which evaporates before reaching the surface.^[2]

The international cloud classification system is based on the fact that
clouds in their most basic forms can show free-convective upward growth
like cumulus, appear in non-convective layered sheets such as stratus, or
take the form of thin fibrous wisps, as in the case of cirrus. Prefixes are
used in connection with clouds to express variations or complexities in
these basic forms or to specify middle or high altitude ranges. These
include /strato-/ for low clouds with limited convection that form mostly
in uneven layers, /cumulo-/ for complex highly-convective storm clouds,
/nimbo-/ for thick layered clouds of some complexity that can produce
moderate to heavy precipitation, /alto-/ for middle clouds, and /cirro-/
for high clouds; the latter two of which may be of simple or moderately
complex structure. Whether or not a cloud is low, middle, or high level
depends on how far above the ground its base forms. Cloud types with
significant vertical extent can form in the low or middle altitude ranges
depending on the moisture content of the air. Clouds in the troposphere
have Latin names

Source: en.wikipedia.org/wiki/Cloud

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