- Industry: Weather
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The American Meteorological Society promotes the development and dissemination of information and education on the atmospheric and related oceanic and hydrologic sciences and the advancement of their professional applications. Founded in 1919, AMS has a membership of more than 14,000 professionals, ...
A series of compounds of entirely anthropogenic origin that were used in industrial applications throughout most of the twentieth century. The major CFCs are CFC-11 (CFCl3) and CFC-12 (CF2Cl2). These compounds have long atmospheric lifetimes (many decades) enabling them to be transported to the stratosphere. The discovery that liberation of chlorine from these species was responsible for the appearance of the antarctic ozone hole each spring led to the introduction of the Montreal Protocol, which banned the use of these species. Although they are no longer in use, their long lifetimes will lead to a very slow removal from the atmosphere.
Industry:Weather
A series of compounds of entirely anthropogenic origin that were used in industrial applications throughout most of the twentieth century. The major CFCs are CFC-11 (CFCl3) and CFC-12 (CF2Cl2). These compounds have long atmospheric lifetimes (many decades) enabling them to be transported to the stratosphere. The discovery that liberation of chlorine from these species was responsible for the appearance of the antarctic ozone hole each spring led to the introduction of the Montreal Protocol, which banned the use of these species. Although they are no longer in use, their long lifetimes will lead to a very slow removal from the atmosphere.
Industry:Weather
The ratio of power received in the transmission channel to power received in the orthogonal channel of a dual-channel radar when a circularly polarized signal is transmitted. Because the stronger component of the circularly polarized signal backscattered from hydrometeors has a polarization orthogonal to the transmitted polarization, the circular depolarization ratio yields a value less than unity or, equivalently, a negative decibel quantity. Note that relative to the receiver channels of the radar, the circular depolarization ratio is defined inversely to the linear depolarization ratio. Compare cancellation ratio.
Industry:Weather
In ocean wave studies, the integral of an energy spectrum. The area under a particular energy spectrum from a given frequency value to infinity is given by the value of the CCS curve at that frequency.
Industry:Weather
Hygroscopic aerosol particles that can serve as nuclei of atmospheric cloud droplets, that is, particles on which water condenses (activates) at supersaturations typical of atmospheric cloud formation (fraction of one to a few percent, depending on cloud type). Concentrations of CCN need to be given in terms of a supersaturation spectrum covering the range of interest or at a specified supersaturation value. Compare condensation nucleus.
Industry:Weather
On a thermodynamic diagram, the point of intersection of a sounding curve (representing the vertical distribution of temperature in an atmospheric column) with the saturation mixing ratio line corresponding to the average mixing ratio in the surface layer (i.e., approximately the lowest 1500 ft). The dry adiabat through this point determines, approximately, the lowest temperature to which the surface air must be heated before a parcel can rise dry-adiabatically to its lifting condensation level without ever being colder than the environment. This temperature, the convective temperature, is a useful parameter in forecasting the onset of convection. See conditional instability, level of free convection.
Industry:Weather
A principal cloud type (cloud genus), appearing as a thin, white patch of cloud without shadows, composed of very small elements in the form of grains, ripples, etc. The elements may be merged or separate, and more or less regularly arranged; they subtend an angle of less than 1° when observed at an angle of more than 30° above the horizon. Holes or rifts often occur in a sheet of cirrocumulus. Cirrocumulus may be composed of highly supercooled water droplets, as well as small ice crystals, or a mixture of both; usually, the droplets are rapidly replaced by ice crystals. Sometime corona or irisation may be observed. Mamma may appear. Small virga may fall, particularly from cirrocumulus castellanus and floccus. (For further details, see cirriform. ) Cirrocumulus, as well as altocumulus, often forms in a layer of cirrus and/or cirrostratus (Cc cirrogenitus or Cc cirrostratogenitus). In middle and high latitudes, cirrocumulus is usually associated in space and time with cirrus and/or cirrostratus; this association occurs less often in low latitudes. Cirrocumulus differs from these other cirriform clouds in that it is not on the whole fibrous, or both silky and smooth; rather, it is rippled and subdivided into little cloudlets. Cirrocumulus is most often confused with altocumulus. It differs primarily in that its constituent elements are very small (see above) and are without shadows. The term cirrocumulus is not used for incompletely developed small elements such as those on the margin of a sheet of altocumulus, or in separate patches at that level. See cloud classification.
Industry:Weather
The pressure unit of the meter–tonne–second system of physical units, equal to 10 millibars or 104 dynes cm−2.
Industry:Weather
A principal cloud type (cloud genus), exceptionally dense and vertically developed, occurring either as isolated clouds or as a line or wall of clouds with separated upper portions. These clouds appear as mountains or huge towers, at least a part of the upper portions of which is usually smooth, fibrous, or striated, and almost flattened as it approaches the tropopause. This part often spreads out in the form of an anvil (incus) or vast plume. Under the base of cumulonimbus, which is often very dark, there frequently exist virga, precipitation (praecipitatio), and low, ragged clouds (pannus), either merged with it or not. Its precipitation is often heavy and always of a showery nature. The usual occurrence of lightning and thunder within or from this cloud leads to its popular appellations: thundercloud, thunderhead (the latter usually refers only to the upper portion of the cloud), and thunderstorm. Cumulonimbus is composed of water droplets and ice crystals, the latter almost entirely in its upper portions. It also contains large water drops, snowflakes, snow pellets, and sometimes hail. The liquid water forms may be notably supercooled. Within a cold air mass in polar regions, the fibrous ice crystal structure may extend virtually throughout the cloud mass. Cumulonimbus always evolves from the further development of cumulus congestus, which, in turn, usually has resulted from the growth of cumulus (Cb cumulogenitus). This complete development may initiate also from stratocumulus castellanus (Cb stratocumulogenitus) or from altocumulus castellanus (Cb altocumulogenitus). In the latter case the cumulonimbus base is particularly high. It may also, but infrequently, develop from a portion of altostratus or nimbostratus (Cb altostratogenitus or Cb nimbostratogenitus). The formative process of cumulonimbus starts as a result of convection from the earth's surface or instability in the upper air, or both simultaneously. It therefore has a predominant diurnal cycle similar to that of cumulus. Cumulonimbus is rare over the polar regions, and becomes increasingly frequent with decreasing latitude, and is, in fact, an almost regular climax of the diurnal cloud cycle in the humid areas of the tropical regions and in humid and unstable air masses penetrating the temperate latitudes. Because of its great vertical size and of the magnitude and variety of forces that act within and upon it, cumulonimbus is a vertical cloud factory. In addition to the complex of accessory features it may possess, which includes tornadoes (tuba), it may also be responsible for the formation of nearly all of the other cloud genera. Cumulus congestus always preexists, and therefore is often easily confused with, cumulonimbus. A cloud is called cumulus congestus until its upper portion begins to show the diffuseness or fibrous quality indicative of ice crystal predominance. Only cumulonimbus is accompanied by lightning, thunder, or hail; only cumulus congestus can rival the intensity of its shower-type precipitation. See cloud classification, thunderstorm.
Industry:Weather
The path of an air parcel with absolute vorticity that remains constant in horizontal flow. Before the advent of modern numerical weather prediction, these trajectories, in conjunction with the theory of Rossby waves, were frequently used to forecast the movement of long tropospheric waves.
Industry:Weather
