- 업종: 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, ...
An arc centered on the zenith and found at least 46° above the sun (or moon). It is produced by the refraction of light through the 90° prisms of ice crystals, having entered through the horizontal bases and passed out through the vertical sides. Normally, the crystals are large, oriented, hexagonal plates. The circumzenithal arc is the high sky counterpart of the circumhorizontal arc. The circumhorizontal arc is low in the sky when the sun is high (above 58° elevation); the circumzenithal arc is high in the sky when the sun is low (below 32° elevation). The majority of circumzenithal arcs are short-lived, short in length and faint or moderately bright. However, very colorful circumhorizontal arcs can occur when the refraction is close to the minimum angle of deviation, corresponding to a solar elevation angle of about 22°.
Industry:Weather
An approximation used in longwave radiative transfer whereby the transmittance of a given path through a nonisothermal gas is related to the transmittance through an equivalent isothermal gas.
Industry:Weather
An approach to the study of climate based on physics and mathematics rather than the more empirical and descriptive methods of traditional climatology. This term was coined by H. Lettau (1969) to describe his one-dimensional representation of climate based on the energy and water balances at the surface.
Industry:Weather
An apparent force, relative to the earth's surface, that causes deflection of moving objects to the right in the Northern Hemisphere and to the left in the Southern Hemisphere due to the earth's rotation. Named for Gustav Gaspard de Coriolis (1792–1843), a French mathematician who published a quantitative mathematical work on the subject in 1835.
Industry:Weather
An aerosol particle forming a center for condensation under extremely high supersaturations (up to 400% for water, but below that required to activate small ions). High supersaturations are produced in a condensation nuclei counter (often using a condensate other than water) to measure the concentration of such particles. Supersaturations greater than a few percent are rarely produced in clouds in the atmosphere but may exist in aircraft exhaust and over hot springs. Nuclei only active at such high suersaturations may coagulate to form larger particles that become condensation nuclei. Compare cloud condensation nuclei.
Industry:Weather
An acceleration of a parcel moving in a relative coordinate system. The total acceleration of the parcel, as measured in an inertial coordinate system, may be expressed as the sum of the acceleration within the relative system, the acceleration of the relative system itself, and the Coriolis acceleration. In the case of the earth moving with angular velocity Ω, a parcel moving relative to the earth with velocity u has the Coriolis acceleration 2Ω × u. If Newton's laws are to be applied in the relative system, the Coriolis acceleration and the acceleration of the relative system must be treated as forces. See apparent force, Coriolis force, inertial force, gravity.
Industry:Weather
An “implicit” method for numerically estimating the derivatives of data on a grid using coefficient templates spanning a more compact range of grid points than the conventional “explicit” differencing template at the same order of accuracy. For example, conventional fourth-order differencing on a uniform grid uses a centered template spanning five values of data; compact fourth-order differencing uses two three-point centered templates, one for the given data and one for the gridded derivatives themselves, which therefore must be solved for simultaneously. The superior accuracy of compact schemes makes them computationally advantageous, provided that the grid geometry is sufficiently regular.
Industry:Weather
Along with the calms of Capricorn, the light, variable winds and calms that occur in the centers of the subtropical high pressure belts over the oceans. They are named after the Tropic of Cancer and Tropic of Capricorn, although their usual position is at about latitudes 30°N and S, the horse latitudes.
Industry:Weather
Against the sun, hence cyclonic, descriptive of motion turning to the left in the Northern Hemisphere and to the right in the Southern Hemisphere; the reverse of cum sole. (These terms were introduced by V. W. Ekman in 1923. ) See also withershins.
Industry:Weather
