Premium
The generation of turbulence and entrainment by buoyancy reversal
Author(s) -
Lock A. P.,
Macvean M. K.
Publication year - 1999
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49712555513
Subject(s) - buoyancy , turbulence , entrainment (biomusicology) , parametrization (atmospheric modeling) , mechanics , boundary layer , sink (geography) , meteorology , scaling , atmospheric sciences , planetary boundary layer , environmental science , physics , geometry , optics , geography , mathematics , radiative transfer , cartography , rhythm , acoustics
In the stratocumulus‐capped atmospheric boundary layer, the evaporation of cloud droplets in mixtures of cloudy and entrained air can, under certain circumstances, reduce their buoyancy to less than that of the surrounding unmixed cloudy air. With a negative buoyancy excess, these parcels will sink away from cloud‐top and therefore generate turbulence within the boundary layer. Dimensional arguments are used to formulate a scaling for the generation of turbulence by this mechanism, referred to as buoyancy reversal, which is found to agree remarkably well with results from idealized high‐resolution three‐dimensional large‐eddy simulations (LES). Furthermore, simple arguments relating the turbulence generation by buoyancy reversal to entrainment at cloud‐top give a simple parametrization for the entrainment rate which is also found to agree very well with the LES.