- 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 fog that does not moisten exposed surfaces. 2. (Rare. ) A condition of reduced visibility due to the presence of dust, smoke, or haze in the air. It is not a true fog.
Industry:Weather
The process by which atmospheric gases and particles are transferred to the surface as a result of random turbulent air motions. See also deposition; compare wet deposition.
Industry:Weather
1. In atmospheric thermodynamics and chemistry, air that is assumed to contain no water vapor. Compare moist air. 2. Generally, air with low relative humidity.
Industry:Weather
A tiny ice particle, about 10–20 μm in diameter, formed by direct freezing of supercooled water droplets with little growth directly from the vapor. The term combines the words drop and crystal. Droxtals cause most of the visibility reduction in ice fog.
Industry:Weather
1. In W. Köppen's 1918 climatic classification, the major category (B climates), which includes steppe climate and desert climate. These climates, unlike the others in his work, are defined strictly by the amount of annual precipitation as a function of seasonal distribution and of annual temperature (see formulas under steppe climate). In contrast are the rainy climates. 2. In C. W. Thornthwaite's 1948 climatic classification, any climate type in which the seasonal water surplus does not counteract seasonal water deficiency; thus it has a moisture index of less than zero. These types include the dry subhumid, semiarid, and arid climates. In contrast are the moist climates. The dry climates are subdivided further according to values of humidity index into the following: little or no water surplus; moderate winter water surplus; moderate summer water surplus; large winter water surplus; large summer water surplus.
Industry:Weather
Computed value related to some of the cumulative effects of a prolonged and abnormal moisture deficiency; an index of hydrological drought corresponding to levels below the mean in streams, lakes, reservoirs, and the like. However, an index of the agricultural drought must relate to the cumulative effects of either an absolute or abnormal transpiration deficit (World Meteorological Organization). See Palmer Drought Severity Index, standard precipitation index.
Industry:Weather
A radiosonde with a parachute dropped from an airplane carrying receiving equipment for the purpose of obtaining an upper-air sounding during descent.
Industry:Weather
A period of abnormally dry weather sufficiently long enough to cause a serious hydrological imbalance. Drought is a relative term, therefore any discussion in terms of precipitation deficit must refer to the particular precipitation-related activity that is under discussion. For example, there may be a shortage of precipitation during the growing season resulting in crop damage (agricultural drought), or during the winter runoff and percolation season affecting water supplies (hydrological drought). Compare dry spell; see absolute drought, partial drought.
Industry:Weather
An instrument used to measure the amount of dew formed on a given surface. One type consists of a hemispheric glass vacuum cup exposed to the atmosphere. Dew forming on the glass surface automatically collects in the bottom of the cup and is weighed at the end of the exposure period. Another form of drosometer, the Duvdevani dew gauge, consists of a block of wood with its surface treated in such a manner that dew forms in characteristic patterns. Photographs are supplied with each instrument to enable the observer to match the dew formation with a set of standards corresponding to a dew “fall” of from 0. 01 to 0. 45 mm (0. 0004–0. 018 in. ).
Industry:Weather
