- 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, ...
A relatively shallow region of cold air of limited horizontal extent. For example, during winter at high latitudes in mountainous regions, cold air can become trapped in valleys, analogous to pools of water. See'' also'' cold-air pool.
Industry:Weather
A relatively dark area on the surface of the sun consisting of a dark central umbra surrounded by a penumbra, which is intermediate in brightness between the umbra and the surrounding photosphere. Sunspots are often nearly circular with a typical dimension of 20 000 km. The strongest solar magnetic fields, up to 4000 gauss, are found within the umbra. Sunspots usually occur in pairs with opposite magnetic polarities. They have a lifetime ranging from a few days to several months. Their occurrence exhibits approximately an 11-year period (the sunspot cycle). See relative sunspot number.
Industry:Weather
A relatively cool layer of air, usually adjacent to a ground surface cooled by net loss of radiation, in which the air temperature increases with height. Sometimes this term is also loosely extended to include layers in which the potential temperature increases with height, that is, to all statically stable layers of air formed by radiatively cooled ground. Radiational cooling is responsible for forming nocturnal stable boundary layers. It is also associated with formation of dew, frost, and fog if the humidity is sufficiently high. It is rare for elevated radiation inversions to form because cooling that creates a relative minimum in potential temperature at some height above the surface would cause cold air to descend from the inversion, creating turbulence that would destroy the inversion.
Industry:Weather
A relationship claimed to exist between solar phenomena and tropospheric weather phenomena.
Industry:Weather
A region of space bounded by arbitrarily selected streamlines of a fluid.
Industry:Weather
A region of sharply reduced precipitation on the lee side of an orographic barrier, as compared with regions upwind of the barrier. Slopes facing windward with respect to prevailing or seasonal moisture-bearing flows typically experience heavy orographic precipitation. To the lee of the barrier, however, the sinking air warms, dries, and becomes more stable, suppressing precipitation. Two dramatic and often-cited examples are the Ghat Mountains of western India, which receive annually more than 600 cm of rainfall at locations on their western slopes but 60 cm or less on their eastern slopes, and the island of Hawaii, where up to 450 cm of rain falls on the slopes facing the northeast trade winds, but less than 100 cm falls at locations on the lee side of the island. A good example of rain shadow in the United States is the region east of the Sierra Nevadas; there the prevailing westerly winds deposit most of their moisture on the western slopes of the range, whereas to the east lies the Great Basin desert.
Industry:Weather
A received signal with a power level that exceeds the dynamic range of the receiver. For such a signal, any increase in the power level causes no appreciable change in the output of the receiver.
Industry:Weather
A region of precipitation from a nimbostratus cloud, which may or may not be an outgrowth of a cumulonimbus cloud, in which the air motions are strong enough for vapor to be condensed or deposited on particles but weak enough that the particles cannot grow effectively by collection of cloud water droplets. Generally the vertical motions are weak enough that the growing particles fall relative to the ground. In especially well-developed stratiform precipitation, precipitating ice particles falling and growing by vapor deposition aggregate to form large snowflakes; then the snowflakes melt and produce a bright band on radar.
Industry:Weather
A record of a plant or crop describing the physiological development stage or physical stage. For example, date of tillering (rapid vegetative plant growth stage in wheat), date of flowering, date of physiological maturity, date of planting, etc. See phenology.
Industry:Weather
