How clouds are formed

Clouds are condensed droplets or ice crystals from atmospheric water vapor. Clouds form by the rising and cooling of air caused by convection, topography, convergence, and frontal lifting. Convection occurs when the Sun’s radiation heats the ground surface, and warm air rises, cooling as it goes. Air also is cooled if an air mass is forced to move upward as a result of higher topography (e.g., a mountain range) in a process known as orographic lifting. Interestingly, when the air mass descends on the other side of the mountain, it warms and the clouds may disappear as the droplets transfer back to vapor. *

The counterclockwise motion of a low-pressure center draws air inward, and the convergence forces the air upward. Air also is lifted and cooled along either a cold front or a warm front. A cold front is the leading edge of an air mass that is colder than the air it is replacing. The front forms a wedge that pushes under the warmer air ahead, lifting it. A warm front is the leading edge of an air mass warmer than the air it is replacing. As the air mass pushes forward, the warm air slides up over the wedge of cold air ahead of it, as shown in the following figure.

Precipitation and Clouds, Formation of
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NWPSAF ECMWF High Resolution Infrared Sounders Aerosol and Cloud Detection

An algorithm to separate and detect clouds from the ground image. The software manual explains more about it.

References

McNally, A.P. and P.D.Watts, 2003. A cloud detection algorithm for high-spectral-resolution infrared sounders Quarterly Journal of the Royal Meteorological Society, 129, 3411-3423.

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Data Sources

Satellite Data of Europe is provided by European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT). Data from the Meteosat, Metop and NOAA satellites are held by the organisation.

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Clouds from Mount Washington B

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Clouds from Mount Washington A

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Timelapse of cloud formation in Orlando 2

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Timelapse of Cloud formation in Orlando

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