- 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. A disturbance in the troposphere of wave length 1000–4000 km (cyclonic scale). They are recognized on synoptic charts as migratory high and low pressure systems. These waves have been identified with the unstable perturbations discussed in connection with baroclinic instability and shearing instability. See short wave, barotropic disturbance. 2. A frontal wave at the crest of which there is a center of cyclonic circulation; therefore, the frontal wave of a wave cyclone.
Industry:Weather
1. A layer in the atmosphere in which are found certain cloud genera. Three such levels are usually defined: high, middle, and low. See cloud classification. 2. At a particular time, the layer in the atmosphere bounded by the limits of the bases and tops of an existing cloud form.
Industry:Weather
1. A nautical term for winds off the Spanish Mediterranean coast that blow from opposite directions at points not far apart. 2. (Rare. ) A change of wind direction with height shown by the movements of clouds at different levels.
Industry:Weather
1. A scheme of distinguishing and grouping clouds according to their appearance, and, where possible, to their process of formation. The one in general use, based on a classification system introduced by Luke Howard in 1803, is that adopted by the World Meteorological Organization and published in the International Cloud Atlas (1956). This classification is based on the determination: 1) genera - the main characteristic forms of clouds; 2) species - the peculiarities in shape and differences in internal structure of clouds; 3) varieties - special characteristics of arrangement and transparency of clouds; 4) supplementary features and accessory clouds - appended and associated minor cloud forms; and 5) mother-clouds - the origin of clouds if formed from other clouds. The ten cloud genera are cirrus, cirrocumulus, cirrostratus, altocumulus, altostratus, nimbostratus, stratocumulus, stratus, cumulus, and cumulonimbus. The fourteen cloud species are fibratus, uncinus, spissatus, castellanus, floccus, stratiform, nebulosus, lenticularis, fractus, humilis, mediocris, congestus, calvus, and capillatus. The nine cloud varieties are intortus, vertebratus, undulatus, radiatus, lacunosus, duplicatus, translucidus, perlucidus, and opacus. The nine supplementary features and accessory clouds are incus, mamma, virga, praecipitatio, arcus, tuba, pileus, velum, and pannus. (Note: Although these are Latin words, it is proper convention to use only the singular endings, e.g., more than one cirrus cloud is cirrus, not cirri. ) 2. A scheme of classifying clouds according to their usual altitudes. Three classes are distinguished: high, middle, and low. High clouds include cirrus, cirrocumulus, cirrostratus, occasionally altostratus, and the tops of cumulonimbus. The middle clouds are altocumulus, altostratus, nimbostratus and portions of cumulus and cumulonimbus. The low clouds are stratocumulus, stratus and most cumulus and cumulonimbus bases, and sometimes nimbostratus. 3. A scheme of classifying clouds according to their particulate composition, namely, water clouds, ice-crystal clouds, and mixed clouds. The first are composed entirely of water droplets (ordinary and/or supercooled), the second entirely of ice crystals, and the third a combination of the first two. Of the cloud genera, only cirrostratus and cirrus are always ice-crystal clouds; cirrocumulus can also be mixed; and only cumulonimbus is always mixed. Altostratus is nearly always mixed, but can occasionally be water. All the rest of the genera are usually water clouds, occasionally mixed; altocumulus, cumulus, nimbostratus, and stratocumulus.
Industry:Weather
1. (Sometimes called asymptote of convergence. ) Any horizontal line along which horizontal convergence of the airflow is occurring. If mass convergence is taking place in a plane near the surface of the earth, the incoming air must be rising at the convergence line. Hence the lines are often associated with convective clouds. 2. Radar signature of horizontal convergence at the surface. See fine line.
Industry:Weather
1. (Or convective current. ) Any current of air involved in convection. In meteorology, this is usually applied to the upward moving portion of a convection circulation, such as a thermal or the updraft in cumulus clouds. 2. Any net transport of electric charge effected through mass motions of some charged medium; any electric current induced by other than electrical forces. In atmospheric electricity, the convection current is part of the air–earth current of charge transfer vertically between the earth's surface and the upper atmosphere. The term includes not only eddy diffusion currents existing in regions of net space charge but also currents due to fall of charged precipitation particles (precipitation current). See convection.
Industry:Weather
1. (Also called cold drop, cold-air drop. ) A region, or “pool,”of relatively cold air surrounded by warmer air; the opposite of a warm pool. This is usually applied to cold air of appreciable vertical extent that has been isolated in lower latitudes as part of the formation of a cut-off low. Cold pools are best identified as thickness minima on thickness charts. They are cyclonic-scale phenomena. 2. Any large-scale mass of cold air; a cold air mass or cold dome.
Industry:Weather
1. (Obsolete. ) Same as westerlies. 2. (Obsolete. ) Same as antitrades.
Industry:Weather
1. (Also called cloud cap. ) An approximately stationary cloud, or standing cloud, on or hovering above an isolated mountain peak. It is formed by the cooling and condensation in moist air forced up over the peak. Compare crest cloud, banner cloud; see lenticularis. 2. Same as pileus.
Industry:Weather
“The study of (ground movement caused by) intensive frost action and of permafrost, their causes and occurrences, and the engineering devices and practices which may be devised to overcome difficulties brought about by them. ” (from Glossary of Arctic and Subarctic Terms 1955).
Industry:Weather
