- 行业: Weather
- Number of terms: 60695
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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, ...
Statistics of the durations of calm periods and storms in connection with wind waves. The expected durations are useful when planning activities that may require a certain number of hours, days or weeks to be completed. For example, the expected duration of wave heights below a specific value are useful when planning critical construction operations at offshore locations.
Industry:Weather
A curve indicating the total time during which event data exceed specified values.
Industry:Weather
In connection with wind waves, the duration is the length of time that winds generating surface waves have been present. This, in addition to the fetch (which is the distance over which these winds act) and wind direction, determines the amplitude and direction of the wind-generated waves.
Industry:Weather
Simplifying approximation that water flow is horizontal and evenly distributed with depth below a water table. The approximation is valid for mildly sloping water tables and for flow that is constrained to shallow depths.
Industry:Weather
A cloud variety composed of superimposed layers, sheets, or patches. These stratified parts, at slightly different levels, are sometimes partly merged. This variety modifies the species fibratus, uncinus, stratiformis, and lenticularis in the genera cirrus, cirrostratus, altocumulus, and altostratus. See cloud classification.
Industry:Weather
A radar device that allows a single antenna to serve as both the transmitter and the receiver. Modern radars use a duplexer consisting of a ferrite circulator and a passive, radioactive gas- primed TR tube to protect the receiver.
Industry:Weather
The vegetative matter, such as leaves, twigs, dead logs, etc. , that covers the ground in the forest; unconsolidated decomposing and partially decomposed organic material immediately under a layer of leaf litter. Duff forms a layer about 5 cm (2 in. ) thick that overlies the soil of a forest floor. Its thermal insulation is an important factor in the formation of permafrost, and the quality and moisture content of duff is significant in considerations of forest fire hazard (fire weather).
Industry:Weather
Applied to the atmosphere and ocean, any region with vertically varying properties such that waves of any kind (e.g., electromagnetic and acoustic) launched in certain directions are guided by or trapped within the region rather than propagating radially from their source. For a duct to exist, attenuation must be negligible over distances comparable to the characteristic linear dimensions of the duct.
Industry:Weather
A radar capable of transmitting signals having two wavelengths and measuring separately the echoes at the two wavelengths. Properties of the scattering medium (cloud, precipitation, or the clear air) may be deduced from the difference in reflectivity or the difference in attenuation at the two wavelengths. See differential reflectivity, differential attenuation.
Industry:Weather
A radar capable of transmitting and receiving two orthogonal polarizations. The transmitted polarization must be switchable at a rate that is fast compared with the timescale of changes in the scattering properties of the target and the propagation medium. Compare dual-channel radar, polarimetric radar, polarization-diversity radar.
Industry:Weather
