Entrainment velocity: Difference between revisions

Latest revision as of 07:59, 29 March 2024

The volume of entrained air per unit area per unit time, which has units of velocity.

It is a measure of dilution of an entity, such as a rising smoke plume, or of a whole layer, such as the atmospheric boundary layer. For a growing atmospheric mixed layer, the rate of rise of the top of the mixed layer z_i equals the entrainment velocity w_e minus any large-scale subsidence w_s that is imposed at the top of the boundary layer. During sunny days over land, the entrainment velocity is proportional to the heat flux from the surface divided by the potential temperature change across the entrainment zone (i.e., the strength of the capping inversion). On windy days, the entrainment velocity is proportional to the turbulence kinetic energy at the top of the boundary layer and is inversely proportional to the potential temperature change across the entrainment zone.
See entrainment rate.

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+{{Term
+|Display title=entrainment velocity
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+|Definitions={{Definition
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+|Num=1
+|Meaning=The volume of entrained air per unit area per unit time, which has units of  [[velocity]].
-<div class="termentry">
+|Explanation=It is a measure of dilution of an entity, such as a rising [[smoke plumes|smoke plume]], or of a whole layer,  such as the [[atmospheric boundary layer]]. For a growing atmospheric [[mixed layer]], the rate of  rise of the top of the mixed layer ''z''<sub>''i''</sub> equals the entrainment velocity ''w''<sub>''e''</sub> minus any large-scale  [[subsidence]] ''w''<sub>''s''</sub> that is imposed at the top of the [[boundary layer]]. During sunny days over land,  the entrainment velocity is proportional to the [[heat flux]] from the surface divided by the [[potential temperature|potential  temperature]] change across the [[entrainment zone]] (i.e., the strength of the [[capping inversion]]).  On windy days, the entrainment velocity is proportional to the [[turbulence kinetic energy]] at the  top of the boundary layer and is inversely proportional to the [[potential temperature]] change across  the entrainment zone. <br/>''See'' [[entrainment rate]].
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-== entrainment velocity ==
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-<div class="definition"><div class="short_definition">The volume of entrained air per unit area per unit time, which has units of  [[velocity]].</div><br/> <div class="paragraph">It is a measure of dilution of an entity, such as a rising [[smoke plumes|smoke plume]], or of a whole layer,  such as the [[atmospheric boundary layer]]. For a growing atmospheric [[mixed layer]], the rate of  rise of the top of the mixed layer ''z''<sub>''i''</sub> equals the entrainment velocity ''w''<sub>''e''</sub> minus any large-scale  [[subsidence]] ''w''<sub>''s''</sub> that is imposed at the top of the [[boundary layer]]. During sunny days over land,  the entrainment velocity is proportional to the [[heat flux]] from the surface divided by the [[potential temperature|potential  temperature]] change across the [[entrainment zone]] (i.e., the strength of the [[capping inversion]]).  On windy days, the entrainment velocity is proportional to the [[turbulence kinetic energy]] at the  top of the boundary layer and is inversely proportional to the [[potential temperature]] change across  the entrainment zone. <br/>''See'' [[entrainment rate]].</div><br/> </div>
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