- 行业: 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, ...
1. Any of the geologic epochs characterized by an ice age. Thus, the Pleistocene epoch may be termed a “glacial epoch. ” 2. Generally, an interval of geologic time that was marked by a major equatorward advance of ice. This has been applied to an entire ice age or (rarely) to the individual glacial “stages” that make up an ice age. The term “epoch” here is not used in the most technical sense of a geologic epoch.
Industry:Weather
1. Any of the geologic periods that embraced an ice age. For example, the Quaternary period may be called a “glacial period. ” 2. Generally, an interval of geologic time that was marked by a major equatorward advance of ice. This may be applied to an entire ice age or (rarely) to the individual glacier “stages” that make up an ice age. The term “period” here is not used in the most technical sense of a geologic period.
Industry:Weather
1. Any process by which the Fourier components of a temporally or spatially varying output are different in amplitude or phase from the corresponding components of an input. Cellophane is a (temporal) filter: The amplitudes of the spectral components of white light (input) incident on the cellophane are different from those of the light it transmits (output). A thermometer is a low-pass filter; all components of air temperature are fed into the thermometer but it passes only the low-frequency components and suppresses the high-frequency components. Optical devices of all kinds are also spatial filters: They may transmit each spatial component of a pattern differently. 2. The separation of a wanted component of a time series from any unwanted residue (noise). See noise filtering.
Industry:Weather
1. For a given locality, the lowest altitude at which glaciers can develop. 2. Same as glacial maximum.
Industry:Weather
1. In British usage, a freezing condition injurious to vegetation, which is considered to have occurred when a minimum thermometer exposed to the sky at a point just above a grass surface records a temperature (grass temperature) of −0. 9°C (30. 4°F) or below. Since 1961 in Britain the statistics refer to the “number of days with grass minimum temperature below 0°C” rather than to ground frost. A fuller discussion is given in McIntosh (1963). See frost. 2. See frozen ground.
Industry:Weather
1. In flow over or past a solid obstacle, that part of the momentum or kinetic energy loss associated with the flow stagnation and related pressure distribution on the obstacle. The form drag scales as the square of the relative velocity, but also depends sensitively on the form of the obstacle. See gravity wave drag. 2. See drag.
Industry:Weather
1. In general, and in popular use, an unusually strong wind. 2. In storm-warning terminology, a wind of 28–47 knots (32–54 mph). In the Beaufort wind scale, a wind with a speed from 28–55 knots (32–63 mph) and categorized as follows: moderate gale, 28–33 knots (Force 7); fresh gale, 34–40 knots (Force 8); strong gale, 41–47 knots (Force 9); and whole gale, 48–55 knots (Force 10).
Industry:Weather
A chart showing the field of D-values (deviations of the actual altitudes along a constant- pressure surface from the standard atmosphere altitude of that surface) in terms of the three dimensions of space and one of time. It is a form of a four-dimensional display of pressure altitude. The space dimensions are represented by D-value contours, and the time dimension is provided by tau-value lines. 4D charts are used primarily for relatively long-distance preflight planning over ocean areas. See also S-values.
Industry:Weather
A characteristic deformation of isobars on a surface synoptic weather chart during a well-developed foehn. The flow produces a pressure ridge over and just windward of the mountain range and a lee trough on the downwind side. The isobars bulge correspondingly, giving a noselike profile in the pressure ridge over the mountains. This configuration is prominent and characteristic of the foehn over the Alps, but over the Rocky Mountains the ridge pattern is less pronounced (perhaps because of the more complicated upstream orography or the presence of cold-air layers, which obscure the surface-pressure pattern, in the valleys of the western United States).
Industry:Weather
A chamber used to check the sensing elements of radiosonde equipment. The chamber houses sources of heat and water vapor plus instruments for measuring temperature, humidity, and pressure. A motor-driven fan maintains air circulation in the chamber.
Industry:Weather
