- 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, ...
The root-mean-square sound pressure at which an average person will begin to experience physical pain from ambient sound. It corresponds to a sound pressure level of 134 dB, that is, 100 N m<sup>−2</sup> or 1 millibar.
Industry:Weather
The particular falling speed, for any given object moving through a fluid medium of specified physical properties, at which the drag forces and buoyant forces exerted by the fluid on the object just equal the gravitational force acting on the object. It falls at constant speed, unless it moves into air layers of different physical properties. In the atmosphere, the latter effect is so gradual that objects such as raindrops, which attain terminal velocity at great heights above the surface, may be regarded as continuously adjusting their speeds to remain at all times essentially in the terminal fall condition. The terminal fall velocity of water droplets in still air can be computed from Stokes's law for drops smaller than 80 μm in diameter. Above that size, empirical values must be used.
Industry:Weather
An instrument for measuring the extinction coefficient of the atmosphere and for the determination of visual range. See runway visual range, visibility meter.
Industry:Weather
A wave that results in no mean displacement of the particles of the fluid in the direction of motion of the wave, in contrast to a wave of translation. Compare transverse wave.
Industry:Weather
A hot wind in Argentina. The name seems to apply to two winds of quite different origin. 1) The most common use is for a dry foehn wind descending the eastern slopes of the Andes in the central Argentine in winter, probably polar maritime air warmed by descent from the crest, which is some 5500 m (18 000 ft) above sea level. It may exceed a velocity of 11 m s<sup>−1</sup> (25 mph). Like the foehn, it sometimes begins with a high foehn (zonda de altura) that overrides a layer of cold air in the lee of the mountains, eventually sweeping it away and descending to ground level as zonda de superficie (or just “zonda”), but this initial cold air mass is not always present. The zondas carry a lot of dust in the dry season. 2) It also describes a hot, humid north wind in the pampas, in advance of a depression moving eastward, and preceding the pampero.
Industry:Weather
Generally, 1 October to 30 September in the Northern Hemisphere, 1 July to 30 June in the Southern Hemisphere; the annual cycle that is associated with the natural progression of the hydrologic seasons. It commences with the start of the season of soil moisture recharge, includes the season of maximum runoff (or season of maximum groundwater recharge), if any, and concludes with the completion of the season of maximum evapotranspiration (or season of maximum soil moisture utilization).
Industry:Weather
Generally, 1 October to 30 September in the Northern Hemisphere, 1 July to 30 June in the Southern Hemisphere; the annual cycle that is associated with the natural progression of the hydrologic seasons. It commences with the start of the season of soil moisture recharge, includes the season of maximum runoff (or season of maximum groundwater recharge), if any, and concludes with the completion of the season of maximum evapotranspiration (or season of maximum soil moisture utilization).
Industry:Weather
Closed isotherms indicating an area of the surface that is relatively warm; most commonly associated areas of human disturbance such as towns and cities. The physiographic analogy derives from the similarity between the pattern of isotherms and height contours of an island on a topographic map. Heat islands commonly also possess “cliffs” at the urban–rural fringe and a “peak” in the most built-up core of the city. The annual mean temperature of a large city (say 10<sup>6</sup> inhabitants) may be 1°–2°C warmer than before development, and on individual calm, clear nights may be up to 12°C warmer. The warmth extends vertically to form an urban heat dome in near calm, and an urban heat plume in more windy conditions.
Industry:Weather
A wave that results in no mean displacement of the particles of the fluid in the direction of motion of the wave, in contrast to a wave of translation. Compare transverse wave.
Industry:Weather
An area of low atmospheric pressure near the surface resulting from heating of the lower troposphere and the subsequent lifting of isobaric surfaces and divergence of air aloft. Thermal lows are common to the continental subtropics in summer; they remain stationary over the warm surface areas that produce them; their cyclonic circulation is generally weak and diffuse; they are nonfrontal. Compare monsoon low.
Industry:Weather
