Difference between revisions of "Condensation"

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<div class="definition"><div class="short_definition">In general, the physical process by which a [[vapor]] becomes a liquid or solid; the  opposite of [[evaporation]], although on the molecular [[scale]], both processes are always occurring.</div><br/> <div class="paragraph">In meteorological usage, this term is applied only to the transformation from vapor to liquid;  any process in which a solid forms directly from its vapor is termed [[deposition]], and the reverse  process [[sublimation]]. In meteorology, condensation is considered almost exclusively with reference  to [[water vapor]] that changes to [[dew]], [[fog]], or [[cloud]]. Condensation in the [[atmosphere]] occurs by  either of two processes: cooling of air to its [[dewpoint]], or addition of enough water vapor to bring  the mixture to the point of [[saturation]] (that is, the [[relative humidity]] is raised to 100 percent).  When either of these processes occurs, condensation ensues only if [[condensation nuclei]] or other  surfaces are present. In the complete absence of such, condensation does not occur at nominal  saturation. The spontaneous formation of liquid or solid droplets from water vapor ([[homogeneous  nucleation]]) is opposed by the surface free-energy increase that attends the creation of new surfaces  of the liquid or solid [[phase]]. Only for extreme [[supersaturation]] does this free-energy balance swing  in favor of [[spontaneous nucleation]].</div><br/> </div>
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<div class="definition"><div class="short_definition">In general, the physical process by which a [[vapor]] becomes a liquid or solid; the  opposite of [[evaporation]], although on the molecular [[scale]], both processes are always occurring.</div><br/> <div class="paragraph">In meteorological usage, this term is applied only to the transformation from vapor to liquid;  any process in which a solid forms directly from its vapor is termed [[deposition]], and the reverse  process [[sublimation]]. In meteorology, condensation is considered almost exclusively with reference  to [[water vapor]] that changes to [[dew]], [[fog]], or [[cloud]]. Condensation in the [[atmosphere]] occurs by  either of two processes: cooling of air to its [[dewpoint]], or addition of enough water vapor to bring  the mixture to the point of [[saturation]] (that is, the [[relative humidity]] is raised to 100 percent).  When either of these processes occurs, condensation ensues only if [[condensation nucleus|condensation nuclei]] or other  surfaces are present. In the complete absence of such, condensation does not occur at nominal  saturation. The spontaneous formation of liquid or solid droplets from water vapor ([[homogeneous nucleation|homogeneous  nucleation]]) is opposed by the surface free-energy increase that attends the creation of new surfaces  of the liquid or solid [[phase]]. Only for extreme [[supersaturation]] does this free-energy balance swing  in favor of [[spontaneous nucleation]].</div><br/> </div>
 
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Latest revision as of 16:40, 25 April 2012



condensation

In general, the physical process by which a vapor becomes a liquid or solid; the opposite of evaporation, although on the molecular scale, both processes are always occurring.

In meteorological usage, this term is applied only to the transformation from vapor to liquid; any process in which a solid forms directly from its vapor is termed deposition, and the reverse process sublimation. In meteorology, condensation is considered almost exclusively with reference to water vapor that changes to dew, fog, or cloud. Condensation in the atmosphere occurs by either of two processes: cooling of air to its dewpoint, or addition of enough water vapor to bring the mixture to the point of saturation (that is, the relative humidity is raised to 100 percent). When either of these processes occurs, condensation ensues only if condensation nuclei or other surfaces are present. In the complete absence of such, condensation does not occur at nominal saturation. The spontaneous formation of liquid or solid droplets from water vapor (homogeneous nucleation) is opposed by the surface free-energy increase that attends the creation of new surfaces of the liquid or solid phase. Only for extreme supersaturation does this free-energy balance swing in favor of spontaneous nucleation.