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Cloud-cover symbols used on weather teleprinters and aviation reports in the US [6] In the early 20th century, it was common for weather maps to be hand drawn. The symbols for cloud cover on these maps, like the modern symbols, were drawn inside the circle marking the position of the weather station making the measurements.
Clouds of the genus nimbostratus tend to bring constant precipitation and low visibility. This cloud type normally forms above 2 kilometres (6,600 ft) [10] from altostratus cloud but tends to thicken into the lower levels during the occurrence of precipitation. The top of a nimbostratus deck is usually in the middle level of the troposphere.
These clouds are often ragged or wispy in appearance. When caught in the outflow beneath a thunderstorm, scud clouds will often move faster than the storm clouds themselves. If the parent cloud that scud clouds pair with were to suddenly dissipate, the pannus cloud accessory would not be able to be told apart from a fractus cloud formation.
The luminance or brightness of a cloud is determined by how light is reflected, scattered, and transmitted by the cloud's particles. Its brightness may also be affected by the presence of haze or photometeors such as halos and rainbows. [114] In the troposphere, dense, deep clouds exhibit a high reflectance (70–95%) throughout the visible ...
Castellanus (clouds made of very narrow columns) are notorious [17] as being unusable by glider pilots. In order for a cloud to have a usable thermal, the updraft column needs to exist under the cloud, in which case the cloud will have a flat base. An altocumulus castellanus, however, can be identified by the lack of a well-defined base. As ...
The yellow color is due to the presence of pollutants in the smoke. Yellowish clouds caused by the presence of nitrogen dioxide are sometimes seen in urban areas with high air pollution levels. [22] Red, orange and pink clouds occur almost entirely at sunrise and sunset and are the result of the scattering of sunlight by the atmosphere.
Polar stratospheric clouds over Western Norway. The stratosphere is very dry; unlike the troposphere, it rarely allows clouds to form.In the extreme cold of the polar winter, however, stratospheric clouds of different types may form, which are classified according to their physical state (super-cooled liquid or ice) and chemical composition.
Asperitas (formerly known as Undulatus asperatus) is a cloud formation first popularized and proposed as a type of cloud in 2009 by Gavin Pretor-Pinney of the Cloud Appreciation Society. Added to the International Cloud Atlas as a supplementary feature in March 2017, it is the first cloud formation added since cirrus intortus in 1951. [2]