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The height of the cloud base can be measured using a ceilometer. This device reflects a beam of light off the cloud base and then calculates its distance using either triangulation or travel time. Alternatively, the cloud base can be estimated from surface measurements of air temperature and humidity by calculating the lifted condensation level.
Cloud chart showing major tropospheric cloud types identified by standard two-letter abbreviations and grouped by altitude and form. See table below for full names and classification. The table that follows is very broad in scope much like the cloud genera template near the bottom of the article and upon which this table is partly based.
The cloud height, more commonly known as cloud thickness or depth, is the distance between the cloud base and the cloud top. [1] It is traditionally expressed either in metres or as a pressure difference in hectopascal (hPa, equivalent to millibar ).
An optical drum ceilometer uses triangulation to determine the height of a spot of light projected onto the base of the cloud. [5] It consists essentially of a rotating projector, a detector, and a recorder. [6] The projector emits an intense beam of light above into the sky at an angle that varies with the rotation.
The base-height range for each level varies depending on the latitudinal geographical zone. [7] Each altitude level comprises two or three genus-types differentiated mainly by physical form. [41] [5] The standard levels and genus-types are summarised below in approximate descending order of the altitude at which each is normally based. [42]
The LCL is a good approximation of the height of the cloud base which will be observed on days when air is lifted mechanically from the surface to the cloud base (e.g. due to convergence of airmasses).
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Cloud top height is often much more variable than cloud base elevation. Clouds greatly affect the transfer of radiation in the atmosphere. In the solar spectral domain, cloud albedo is directly related to the nature, size and shape of cloud particles, which themselves are affected by the height of the cloud top.