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Clouds ~ 1920 US Department of Agriculture Educational Film Service
🕑 Added 2020-12-05 22:38:57 +0000 UTCmore at http://quickfound.net/
Silent, with title cards. 'Directed by C.C. Clark and Raymond Evans. Photographed by Corliss Cramer. Contribution from The Weather Bureau.'
Originally a public domain film from the Prelinger Archives, slightly cropped to remove uneven edges, with the aspect ratio corrected, and one-pass brightness-contrast-color correction & mild video noise reduction applied.
https://en.wikipedia.org/wiki/Cloud
Wikipedia license: http://creativecommons.org/licenses/by-sa/3.0/
In meteorology, a cloud is an aerosol consisting of a visible mass of minute liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body. Water or various other chemicals may compose the droplets and crystals. On Earth, clouds are formed as a result of saturation of the air when it is cooled to its dew point, or when it gains sufficient moisture (usually in the form of water vapor) from an adjacent source to raise the dew point to the ambient temperature. They are seen in the Earth's homosphere (which includes the troposphere, stratosphere, and mesosphere). Nephology is the science of clouds, which is undertaken in the cloud physics branch of meteorology.
...Cloud types in the troposphere, the atmospheric layer closest to Earth's surface, have Latin names... stratiform sheets, cirriform wisps and patches, stratocumuliform layers (mainly structured as rolls, ripples, and patches), cumuliform heaps, and very large cumulonimbiform heaps that often show complex structure... The Latin names for applicable high-level genera carry a cirro- prefix, and an alto- prefix is added to the names of the mid-level genus-types... Very low stratiform clouds that extend down to the Earth's surface are given the common names fog and mist...
Taken as a whole, homospheric clouds can be cross-classified by form and level to derive the ten tropospheric genera, the fog and mist that forms at surface level, and several additional major types above the troposphere. The cumulus genus includes three species that indicate vertical size. Clouds with sufficient vertical extent to occupy more than one altitude level are officially classified as low- or mid-level according to the altitude range at which each initially forms. However they are also more informally classified as multi-level or vertical...
Physical forms
Clouds in the troposphere assume five physical forms based on structure and process of formation...
Stratiform
Non-convective stratiform clouds appear in stable airmass conditions and, in general, have flat sheet-like structures that can form at any altitude in the troposphere. The stratiform group is divided by altitude range into the genera cirrostratus (high-level), altostratus (mid-level), stratus (low-level), and nimbostratus (multi-level). Fog is commonly considered a surface-based cloud layer...
Cirriform
Cirriform clouds in the troposphere are of the genus cirrus and have the appearance of detached or semi-merged filaments. They form at high tropospheric altitudes in air that is mostly stable with little or no convective activity...
Stratocumuliform
Clouds of this structure have both cumuliform and stratiform characteristics in the form of rolls, ripples, or elements. They generally form as a result of limited convection in an otherwise mostly stable airmass topped by an inversion layer. If the inversion layer is absent or higher in the troposphere, increased air mass instability may cause the cloud layers to develop tops in the form of turrets consisting of embedded cumuliform buildups. The stratocumuliform group is divided into cirrocumulus (high-level), altocumulus (mid-level), and stratocumulus (low-level).
Cumuliform
Cumuliform clouds generally appear in isolated heaps or tufts. They are the product of localized but generally free-convective lift where there are no inversion layers in the troposphere to limit vertical growth. In general, small cumuliform clouds tend to indicate comparatively weak instability. Larger cumuliform types are a sign of greater atmospheric instability and convective activity. Depending on their vertical size, clouds of the cumulus genus type may be low-level or multi-level with moderate to towering vertical extent.
Cumulonimbiform
The largest free-convective clouds comprise the genus cumulonimbus which have towering vertical extent. They occur in highly unstable air and often have fuzzy outlines at the upper parts of the clouds that sometimes include anvil tops. These clouds are the product of very strong convection that can penetrate the lower stratosphere.
