- 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, ...
1. The dissipation of a front or frontal zone. 2. In general, a decrease in the horizontal gradient of an air mass property, principally density, and the dissipation of the accompanying features of the wind field.
Industry:Weather
1. The assumption that the horizontal wind may be represented by the geostrophic wind. 2. Same as quasigeostrophic approximation.
Industry:Weather
1. The annual spring rise of streams in cold climates as a result of melting snow. 2. A flood resulting from either rain or melting snow. In this sense it is usually applied only to small streams and to floods of minor severity. 3. A small freshwater stream.
Industry:Weather
1. See freezing. 2. The condition that exists when, over a widespread area, the surface temperature of the air remains below freezing (0°C) for a sufficient time to constitute the characteristic feature of the weather. This is a general term, and the time period necessary is usually considered to be two or more days; only the hardiest herbaceous crops survive. It differs from a dry freeze or black frost, for these terms are usually used to describe purely local freezing due to chilling of the surface air by rapid radiation from a restricted portion of the earth. Compare light freeze, hard freeze, killing freeze.
Industry:Weather
1. Pertaining to ice, especially in great masses, such as sheets of land ice or glaciers. 2. Pertaining to an interval of geologic time that was marked by an equatorward advance of ice during an ice age; the opposite of interglacial phase. These intervals are variously called glacial periods, glacial epochs, glacial “stages,” etc.
Industry:Weather
1. In open channel flow, a manufactured conduit (usually rectangular in shape) with a portion having a constricted cross section, which may be used to control and measure streamflow. 2. In geomorphology, a narrow, steep-sided valley. 3. In hydraulics, a channel used for studying the flow of fluids under gravity. The fluid is pumped from a sump to a stilling tank that acts as a reservoir from which the fluid is discharged down the flume at varying speeds. The motion is viewed from above or through glass sides.
Industry:Weather
1. In micrometeorology, the region of ground that affects a turbulent flux measurement above the surface. Also known as the source-weight distribution function, the footprint can figuratively be described as the ensemble average field-of-view of a turbulent flux measurement. The footprint function is derived from a suitable model of turbulent transport. Alternately, an analogous footprint can be defined for scalar concentrations or for radiative fluxes. 2. In remote sensing, the instantaneous field-of-view of an airborne remote sensing instrument.
Industry:Weather
1. In meteorology, generally, the interface or transition zone between two air masses of different density. Since the temperature distribution is the most important regulator of atmospheric density, a front almost invariably separates air masses of different temperature. Along with the basic density criterion and the common temperature criterion, many other features may distinguish a front, such as a pressure trough, a change in wind direction, a moisture discontinuity, and certain characteristic cloud and precipitation forms. The term front is used ambiguously for 1) frontal zone, the three- dimensional zone or layer of large horizontal density gradient, bounded by 2) frontal surfaces across which the horizontal density gradient is discontinuous (frontal surface usually refers specifically to the warmer side of the frontal zone); and 3) surface front, the line of intersection of a frontal surface or frontal zone with the earth's surface or, less frequently, with a specified constant-pressure surface. Types of front include polar front, arctic front, cold front, warm front, and occluded front. See also anafront, katafront, intertropical front, secondary front, upper front. 2. See wave front.
Industry:Weather
