- 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 general term applied to the atmosphere above the troposphere. See atmospheric shell.
Industry:Weather
The general term for a cyclone that originates over the tropical oceans. This term encompasses tropical depressions, tropical storms, hurricanes, and typhoons. At maturity, the tropical cyclone is one of the most intense and feared storms of the world; winds exceeding 90 m s<sup>−1</sup>(175 knots) have been measured, and its rains are torrential. Tropical cyclones are initiated by a large variety of disturbances, including easterly waves and monsoon troughs. Once formed, they are maintained by the extraction of latent heat from the ocean at high temperature and heat export at the low temperatures of the tropical upper troposphere. After formation, tropical cyclones usually move to the west and generally slightly poleward, then may “recurve,” that is, move into the midlatitude westerlies and back toward the east. Not all tropical cyclones recurve. Many dissipate after entering a continent in the Tropics, and a smaller number die over the tropical oceans. Tropical cyclones are more nearly circularly symmetric than are frontal cyclones. Fully mature tropical cyclones range in diameter from 100 to well over 1000 km. The surface winds spiral inward cyclonically, becoming more nearly circular near the center. The wind field pattern is that of a circularly symmetric spiral added to a straight current in the direction of propagation of the cyclone. The winds do not converge toward a point but rather become, ultimately, roughly tangent to a circle bounding the eye of the storm. Pressure gradients, and resulting winds, are nearly always much stronger than those of extratropical storms. The cloud and rain patterns vary from storm to storm, but in general there are spiral bands in the outer vortex, while the most intense rain and winds occur in the eyewall. Occasionally, multiple eyewalls occur and evolve through a concentric eyewall cycle. Tropical cyclones are experienced in several areas of the world. In general, they form over the tropical oceans (except the South Atlantic and the eastern South Pacific) and affect the eastern and equatorward portions of the continents. They occur in the tropical North Atlantic (including the Caribbean Sea and Gulf of Mexico), the North Pacific off the west coast of Mexico and occasionally as far west as Hawaii, the western North Pacific (including the Philippine Islands and the China Sea), the Bay of Bengal and the Arabian Sea, the southern Indian Ocean off the coasts of Madagascar and the northwest coast of Australia, and the South Pacific Ocean from the east coast of Australia to about 140°W. By international agreement, tropical cyclones have been classified according to their intensity as follows: 1) tropical depression, with winds up to 17 m s<sup>−1</sup>(34 knots); 2) tropical storm, with winds of 18–32 m s<sup>−1</sup>(35–64 knots); and 3) severe tropical cyclone, hurricane or typhoon, with winds of 33 m s<sup>−1</sup>(65 knots) or higher. It should be noted that the wind speeds referred to above are 10-min average wind speeds at standard anemometer level (10 m), except that in the United States, 1-min average wind speeds are used.
Industry:Weather
The general term for instruments used to make direct measurements of visual range in the atmosphere or of the physical characteristics of the atmosphere that determine the visual range. Visibility meters may be classified according to the quantities that they measure. Telephotometers and transmissometers measure the transmissivity or, alternatively, the extinction coefficient of the atmosphere. Nephelometers measure the scattering function of the particles suspended in the atmosphere. A third category of visibility meters makes use of an artificial “haze” of variable density that is used to obscure a marker at a fixed distance from the visibility meter.
Industry:Weather
The global database for an expert system that contains all known facts about the situation to which the expert system is currently being applied.
Industry:Weather
The great circle of transition from daylight to darkness on the earth's surface. The terminator appears in visible environmental satellite imagery as a gradual change from easily detectable cloud features to nearly black imagery.
Industry:Weather
The highest and lowest values of temperatures attained at a specified location during a given time interval, for example, daily, monthly, or seasonal. In climatology, if this is the whole period for which observations are available, it is called the “absolute extreme. ”
Industry:Weather
The incorporation of laminar air having high velocity into a turbulent region of lower mean velocity.
Industry:Weather
The indefinite range of wavelengths of visible radiation, sometimes taken (for convenience) to lie between 400 and 700 nm. Radiation with wavelengths less than 400 nm is called ultraviolet radiation; radiation with wavelengths greater than 700 nm is called infrared radiation.
Industry:Weather
