- 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 process or condition in which radiation travels between source and receiver via more than one propagation path. Because there can be only one “direct” path, some process of reflection, refraction, or scattering must account for multipath propagation.
Industry:Weather
A frequent condition in which the tropopause appears not as a continuous single “surface” of discontinuity between the troposphere and stratosphere but as a series of quasi-horizontal “leaves” that are partly overlapping in steplike arrangement. The multiple tropopause is most common above regions of large horizontal temperature contrast in the troposphere. In the more extreme conditions the components of the multiple tropopause are not distinct, and the tropopause is then just a deep zone of transition between troposphere and stratosphere.
Industry:Weather
Scattering of radiation, usually electromagnetic but possibly acoustic, by an array of objects (e.g., atoms, molecules, particles) each of which is excited to scatter (radiate) not only by an external source but also by the scattered radiation from the other objects in the array. Multiple scattering is distinguished from single scattering, an idealization strictly realized only with a single object excited by an infinitely distant source. Scattering as a consequence solely of excitation by the external source is sometimes referred to as primary scattering, the remaining scattering as secondary scattering, which is misleading in that it can be decomposed into an infinite series of primary, secondary, tertiary, and higher-order scattering. Multiple scattering can be classified according to the coherence properties of the array and the external source. For incoherent multiple scattering, phase differences of scattered waves are random, and scattered powers are additive. For coherent multiple scattering, phase differences of scattered waves are not random, and scattered fields are additive. Incoherent and coherent multiple scattering are idealizations. An example of (primarily) incoherent multiple scattering is scattering of sunlight by thick clouds. An example of (mostly) coherent multiple scattering is specular reflection by a glass of water. Scattering by a single cloud droplet is an example of scattering by a coherent array the water molecules in the droplet stick together (cohere) in the sense that the phase differences between their individual scattered waves are fixed whereas scattering by the entire cloud is incoherent in the sense that for droplets separated by random distances large compared with the wavelength, the phase differences between waves scattered by individual droplets are essentially random.
Industry:Weather
Hailstone growth by several ascents and descents within a cloud. At present, this is considered a common occurrence, but not a necessary one for the formation of hail.
Industry:Weather
A chronograph used to make a time record of certain measured meteorological elements. The most common type, the triple register, records wind direction and speed, duration of sunshine, and amount of rainfall (sensed, respectively, by a contact anemometer, Marvin sunshine recorder, and tipping-bucket rain gauge). The register consists of a rotating, clock-driven drum on a helical axis, a separate pen for each element, and the actuating mechanism for the pens. Double registers are also used. Multiple registers of this type are becoming obsolete.
Industry:Weather
In air navigation, a method of pressure-pattern flight utilizing a set of drift-correction angles applied over successive segments of the flight route. Multiple drift corrections are necessary to maintain a prescribed course over the earth when a single drift correction would result in a relatively meandering course. See minimal flight.
Industry:Weather
The process or condition in which radiation travels between source and receiver via more than one propagation path. Because there can be only one “direct” path, some process of reflection, refraction, or scattering must account for multipath propagation.
Industry:Weather
Generally, the climate of high elevations. Mountain climates are distinguished by the departure of their characteristics from those of surrounding lowlands, and the one common basis for this distinction is that of atmospheric rarefaction. Aside from this, great variety is introduced by differences in latitude, elevation, and exposure to the sun. Thus, there exists no single, clearly defined, mountain climate. The most common climatic results of high elevation are those of decreased pressure, reduced oxygen availability, decreased temperature, and increased insolation; the last two combine to produce a typical “hot sun and cold shade” condition. Precipitation is heavier on the windward side of a mountain barrier than on the leeward (orographic precipitation), and on the windward side it increases upward to the zone of maximum precipitation, then decreases again. On many tropical mountains the forest zone extends into the level of average cloud height, which causes an excessively damp climate and produces the so-called fog forest. The orography gives rise to many local winds, chief among which are the foehn, mountain and valley winds, mountain-gap winds, and downslope winds of many sorts. Great interest in mountain climate has centered in the relatively well- populated, equatorial Andes. There, four zones of elevation are delimited: tierra caliente (hot land); tierra tamplada (temperate land); tierra fria (cool land); and tierra helada (land of frost).
Industry:Weather
Propagation of acoustic or electromagnetic radiation between two points along two or more paths because of the nonuniformity of the propagating medium.
Industry:Weather
A radar capable of deriving more than one quantity from observations of a target. In meteorological applications, the term is usually applied to radars capable of measuring either 1) reflectivity and at least one polarization-dependent quantity, or 2) reflectivity and at least one wavelength-dependent quantity. The term is not ordinarily applied to radars that operate with a single wavelength and measure only reflectivity and Doppler velocity. Compare polarimetric radar.
Industry:Weather
