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acclimation—1. Basically, same as acclimatization. 2. Adaptation of living organisms to all aspects of the environment, not just the climatic. Examples of acclimation would be adjustment of plants to growth at elevated atmospheric carbon dioxide concentrations or to soil water deficits.
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acclimatization—1. (Also called acclimation.) The process by which a living organism becomes adapted to a change of climatic environment. There has been a growing amount of research on the acclimatization of man to extreme environments such as polar and tropical regions and high altitudes. These studies are directed toward 1) determination of the internal physiological changes or skin changes produced by exposure to new climates, 2) determination of criteria for preselection (i.e., selecting the most adaptable type of man for a particular climate), and 3) development of external means of aiding adaptation (e.g., preconditioning, and modification of habits, diet, and clothing). As to usage, “acclimatization” has long been considered to be equivalent to “acclimation.” In some quarters, however, a fine distinction is drawn by calling “acclimation” a purely natural process (or state), and “acclimatization” a process (or state) influenced by human agency. The recent trend, at least in the United States, is to use “acclimatization” as the all-inclusive technical term, and to leave “acclimation” (which never was accepted in Great Britain) to more or less loose popular usage. 2. The state or degree of adaptation to climate.
Castellani, Sir Aldo, 1938: Climate and Acclimatization, 2d ed., 146–176.
Newburgh, L. H., ed., 1949: Physiology of Heat Regulation and the Science of Clothing, 3–67.
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accretion—1. (Sometimes incorrectly called coagulation.) In cloud physics, usually the growth of an ice hydrometeor by collision with supercooled cloud drops that freeze wholly or partially upon contact. May also refer to the collection of smaller ice particles. This has been called a form of agglomeration and is analogous to coalescence, in which liquid drops collect other liquid drops. See ice accretion; compare coagulation. 2. In cloud modeling, the collection of cloud drops by drizzle drops and raindrops. This nomenclature is used along with autoconversion and self collection to distinguish among three subprocesses, evident from numerical results, responsible for the growth of the drop-size distribution by the collision–coalescence process.
Kessler, E., 1969: On the Disribution and Continuity of Water Substance in Atmospheric Circulation, Amer. Meteor. Soc., Boston, 84 pp.
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accumulated cooling—The total cooling since the time in the evening when the turbulent heat flux near the ground produces a net heat flow from the earth to the atmosphere; used to measure or predict evolution of the stable boundary layer. It is defined as the integral of the surface kinematic heat flux  over time, starting from the time t0 just before sunset when the flux changes from positive to negative, and ending at any time te before the flux changes sign back to positive. Dimensions are temperature times length, such as (K·m). In the absence of advection and direct radiative cooling of the air, accumulated cooling (AC) also equals the area under the potential temperature profile z(θ), integrated from the surface potential temperature θs to the residual-layer potential temperature θRL, that is, 
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accumulated temperature—(Or cumulative temperature.) In Great Britain, the accumulated excess of temperature above a given standard temperature. It is expressed in degree-hours or degree-days. For each day, degree-hours are determined as the product of the length of time, in hours, during which temperatures are above the standard, and the amount, in degrees, by which the mean temperature of the period exceeds the standard. Division of the resulting degree-hour value by 24 gives a value in degree-days. Summation of either over the period of interest creates the accumulated temperature. The concept of accumulated temperature was introduced into plant geography by A. de Candolle (1855); his standard temperature was 6°C (42.8°F), below which he considered that no vegetative growth took place. It was introduced into agricultural meteorology in Britain in 1878, when accumulated temperatures in excess of 42°F were first published regularly in the Weekly Weather Report. These were calculated from the daily maximum and minimum temperatures. In heating calculations, a form of accumulated temperature is calculated as the number of degree-days below the standard, which is taken as 65°F in the United States and 60°F in Great Britain. Since the standard temperatures differ, degree-days are not interchangeable between the two countries.
de Candolle, A., 1855: Géographie Botanique Raisonné, 2 vols., Paris: V. Masson
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accumulation mode—Aerosol particles in the size range 0.5–2 μm in diameter. The name arises from the fact that particles in this size range are aerodynamically stable and do not settle out, nor do they agglomerate to form larger particles; thus they tend to accumulate in the atmosphere. See also agglomeration.
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accumulation rain gauge—(Also called accumulative rain gauge.) A class of rain gauges in which the precipitation is accumulated over time. The depth of accumulated precipitation can be determined by the level of a float, by weighing, or by manual direct measurement of water depth. For long-term, unattended operation a known amount of liquid that prevents evaporation is placed in the collection container.
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