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A buoyancy‐based mixing‐length proposal for cloudy boundary layers
Author(s) -
Sáanchez E.,
Cuxart J.
Publication year - 2004
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 - 10.1256/qj.03.121
Subject(s) - parametrization (atmospheric modeling) , buoyancy , turbulence kinetic energy , mixing (physics) , turbulence , convection , atmospheric sciences , environmental science , boundary layer , meteorology , mechanics , geology , physics , quantum mechanics , radiative transfer
Abstract The parametrization of boundary‐layer clouds is approached here using a turbulence–kinetic energy closure, in conservative variables for non‐precipitating processes and through a new proposal for the turbulence mixing length. A subgrid condensation scheme able to treat partially saturated conditions in a model grid cell is also necessary. An extension of the buoyancy‐based Bougeault–Lacarrère mixing length is proposed, to take into account moist processes, and specifically the effects of phase changes. The asymmetry between upward and downward mixing processes is also considered for partial cloudiness conditions. The new proposal is tested for stratocumulus‐capped marine boundary layers and for shallow cumulus convection, both over land and sea. The validation ismade against large‐eddy simulation results obtained from model intercomparison cases, for stationary regimes as a first step, and then for the diurnal evolution of marine stratocumulus and shallow convection over land. Copyright © 2004 Royal Meteorological Society