- 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. In meteorology, a surface low pressure area or mesolow (or the envelope of several low pressure areas) to the rear of a squall line; most commonly found in squall lines with trailing stratiform precipitation regions, in which case the axis of the low is positioned near the back edge of the stratiform rain area. 2. In fluid dynamics, a low pressure area on the downstream side of an object embedded in a flow.
Industry:Weather
1. The disturbed state of a medium through which any wave form of energy is being propagated. 2. In synoptic meteorology, same as wave cyclone, but usually denoting an early stage in the development of a wave cyclone, or a poorly developed one. See disturbance.
Industry:Weather
1. In meteorology, a surface low pressure area or mesolow (or the envelope of several low pressure areas) to the rear of a squall line; most commonly found in squall lines with trailing stratiform precipitation regions, in which case the axis of the low is positioned near the back edge of the stratiform rain area. 2. In fluid dynamics, a low pressure area on the downstream side of an object embedded in a flow.
Industry:Weather
1. (Or geothermal gradient. ) According to Smithsonian Physical Tables, the rate of variation of temperature in soil and rock from the surface of the earth down to depths of the order of kilometers. It varies greatly from place to place, depending on the geological history of the region, the radioactivity of the underlying rocks, and the conductivity of the upper rocks. An average is about +10°C per km. 2. Same as temperature gradient. See Also lapse rate.
Industry:Weather
The pressure exerted by the molecules of a given vapor. For a pure, confined vapor, it is that vapor's pressure on the walls of its containing vessel; for a vapor mixed with other vapors or gases, it is that vapor's contribution to the total pressure (i.e., its partial pressure). In meteorology, vapor pressure is used almost exclusively to denote the partial pressure of water vapor in the atmosphere. Care must be exercised in interpreting the term's meaning as used in other branches of science. See saturation vapor pressure, equilibrium vapor pressure.
Industry:Weather
1. The wind system, occupying most of the Tropics, that blows from the subtropical highs toward the equatorial trough; a major component of the general circulation of the atmosphere. The winds are northeasterly in the Northern Hemisphere and southeasterly in the Southern Hemisphere; hence they are known as the northeast trades and southeast trades, respectively. The trade winds are best developed on the eastern and equatorial sides of the great subtropical highs, especially over the Atlantic. In the Northern Hemisphere they begin as north-northeast winds at about latitude 30°N in January and latitude 35°N in July, gradually veering to northeast and east-northeast as they approach the equator. Their southern limit is a few degrees north of the equator. The southeast trades occupy a comparable region in the Southern Hemisphere and similarly change from south-southeast on their poleward side to southeast near the equator. In the Pacific, the trade winds are properly developed only in the eastern half of that ocean, and in the Indian Ocean, only south of about 10°S. They are primarily surface winds, their usual depth being from 3000 to 5000 ft, although they sometimes extend to much greater altitudes. They are characterized by great constancy of direction and, to a lesser degree, speed; the trades are the most consistent wind system on earth. See antitrades, tropical easterlies, equatorial easterlies. 2. A name given to the prevailing westerlies in California and to the northwest winds that blow in Oregon in summer.
Industry:Weather
1. Any one of several possible horizontal belts of vegetation type found in mountainous terrain. These belts are primarily the result of vertical temperature variation. See, for example, frostless zone, timber line. 2. An elevation band along mountain and other terrain slopes where nighttime surface temperatures remain relatively mild compared with temperatures above and below. Drainage winds carry the coldest air down the slopes to the bottom of the valley. The belt of warmer air (thermal belt) lies above this pool of cold air. Above the warm belt, temperature exhibits its normal decline with elevation, augmented by increased radiation loss from lower air density and lower moisture content at higher altitudes. The impact of this milder slope climate is a longer growing season, an earlier leafing out and blossoming of trees and other vegetation, and the ability to grow crops that could not survive at lower or higher elevations (e.g., vineyards). Geiger (1965) suggests that this effect influenced early settlement locations: “In Germany this area was preferred for the earliest villages, monasteries, and country houses. ”
Industry:Weather
The situation in which the vertical wind shear vector does not change direction with height. Presented on a hodograph, unidirectional shear appears as a straight line. Unidirectional vertical wind shear does not always indicate unidirectional winds, since a straight-line hodograph can result from many different wind profiles.
Industry:Weather
1. Specifically, the dominant west-to-east motion of the atmosphere, centered over the middle latitudes of both hemispheres. At the earth's surface, the westerly belt (or west-wind belt, etc. ) extends, on the average, from about 35° to 65° latitude. At upper levels, the westerlies extend farther equatorward and poleward. The equatorward boundary is fairly well defined by the subtropical high pressure belt; the poleward boundary is quite diffuse and variable. Especially in the Northern Hemisphere, even the annual average westerlies are markedly enhanced in some regions, namely, the jet streams. See polar vortex, antitrades, tropical easterlies, zonal index. 2. Generally, any winds with components from the west. 3. See equatorial westerlies.
Industry:Weather
A noble gas, atomic number 54, atomic weight 131. 3; a heavy, unreactive, colorless element found in the atmosphere to the extent of only 0. 0000087% by volume.
Industry:Weather
