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Unified treatment of dry convective and stratocumulus‐topped boundary layers in the ECMWF model
Author(s) -
Köhler M.,
Ahlgrimm M.,
Beljaars A.
Publication year - 2011
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.713
Subject(s) - parametrization (atmospheric modeling) , entrainment (biomusicology) , environmental science , atmospheric sciences , troposphere , marine stratocumulus , boundary layer , convection , meteorology , geology , radiative transfer , physics , mechanics , aerosol , quantum mechanics , rhythm , acoustics
The unified parametrization of the dry boundary layer and stratocumulus in the ECMWF model is described using the eddy diffusivity mass‐flux framework. Model simulations are compared to observations at a few selected research field experiments, to ISCCP cloud cover, to LIDAR from space cloud observations, to SYNOP observations over Europe and to the climatology. It is shown that the new stratocumulus formulation improved the quality of the stratocumulus simulations rather dramatically. The key ingredients are: (i) mixing in moist conserved variables, (ii) diffusion related to cloud‐top cooling, (iii) an additional mass‐flux term, (iv) an entrainment parametrization and (v) a switching between shallow cumulus and stratocumulus based on lower tropospheric stability. To illustrate the relevance of various aspects, the sensitivity to different parameters is also presented. Copyright © 2011 Royal Meteorological Society