- 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, ...
A fluid having density variation along the axis of gravity, usually implying upward decrease of density, that is, a stratification characterized by static stability.
Industry:Weather
A flue gas system that removes most of the sulfur dioxide, SO<sub>2</sub>, from exhaust gases; generally used for large coal-fired boilers. See'' also'' limestone scrubbing.
Industry:Weather
A flat or gently undulating plain that is grassy and generally treeless; specifically, such an area in southern Canada and the northern and central United States where it extends from the foothills of the Rocky Mountains to about 88°W longitude. Its climate, with light summer rains and high summer temperatures, is highly favorable for the growth of cereals, but there is a considerable risk of drought especially in certain portions, where a semiarid climate (steppe climate) prevails. The prairie is similar, but not completely analogous, to the steppe regions of Europe and Asia.
Industry:Weather
A flash of red light seen on or (seemingly) adjacent to the lower rim of the low sun (at either sunrise or sunset). Much of what is said about the green flash applies to the red flash, only transferred to the base of the sun and applied to multiple images of the lower red rim. During a sunset, an island of red light will sometimes form just below the rest of the sun, proceed to join the main disc, and then progress up the sides of the sun as serrations. The red flash is not perceived as being as striking an event as the green flash if for no other reason than that its color is more characteristic of the low sun.
Industry:Weather
A finite difference approximation in which some terms producing time change are specified at an earlier time level. The approximation (''f<sup>n'' + 1</sup> − ''f<sup>n'' − 1</sup>)/2Δ''t'' = ''g''(''f<sup>n'' + 1</sup>) + ''h''(''f<sup>n</sup>'') (where superscript ''n'' denotes a point in time, separated by step Δ''t'' from the prior (''n'' − 1) and subsequent (''n'' + 1) discrete time level) is an example of a semi-implicit approximation to ''df''/''dt'' = ''g''(''f'') + ''h''(''f''). Semi-implicit approximations may increase computational efficiency when ''g'' produces relatively higher frequencies or more rapid time changes in ''f'' than does ''h''. See implicit time difference.
Industry:Weather
A filament-like protuberance from the chromosphere of the sun. Prominences can be observed visually (optically) whenever the sun's disk is masked, as during an eclipse or by using a coronagraph; and can be observed instrumentally by filtering in certain wavelengths, as with a spectroheliograph. A typical prominence is 6000 to 12 000 km thick, 60 000 km high, and 200 000 km long. These features appear as filaments when they are seen against the solar disk.
Industry:Weather
A faint band, purple in color, seen over much of the solar sky during a clear twilight. The purple light exists when sun elevation −2° < ''h''<sub>0</sub> < −6°. Its azimuthal width is ∼40°–80°, and its vertical or elevation-angle width is ∼10°–15°. Maximum luminance occurs at ''h''<sub>0</sub> ∼ −4°, and the area of purple light steadily descends toward the solar point during evening twilight. At ''h''<sub>0</sub> ∼ −7°, the bright segment replaces the purple light.
Industry:Weather
