View source for Atmospheric boundary layer



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== atmospheric boundary layer ==
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<div class="definition"><div class="short_definition">(Abbreviated ABL; <br/>''also called'' boundary layer, planetary boundary  layer.) The bottom layer of the [[troposphere]] that is in contact with the surface of the earth.</div><br/> <div class="paragraph">It is often turbulent and is capped by a [[static stability|statically stable]] layer of air or [[temperature inversion]].  The ABL depth (i.e., the [[inversion]] height) is variable in time and space, ranging from tens of  meters in strongly statically stable situations, to several kilometers in convective conditions over  deserts. During [[fair]] weather over land, the ABL has a marked [[diurnal]] cycle. During daytime, a  [[mixed layer]] of vigorous [[turbulence]] grows in depth, capped by a statically stable [[entrainment zone|entrainment  zone]] of intermittent turbulence. Near [[sunset]], turbulence decays, leaving a [[residual layer]] in place  of the mixed layer. During nighttime, the bottom of the residual layer is transformed into a statically  [[stable boundary layer]] by contact with the radiatively cooled surface. [[cumulus|Cumulus]] and [[stratocumulus]]  clouds can form within the top portion of a humid ABL, while [[fog]] can form at the bottom of a  stable boundary layer. The bottom 10% of the ABL is called the [[surface layer]]. <br/>''Compare'' [[Ekman layer|Ekman  layer]].</div><br/> </div><div class="reference">Stull, R. B. 1988. An Introduction to Boundary Layer Meteorology.  666 pp. </div><br/> 
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