Royal Dutch Meteorological Institute; Ministery Of Infrastructure And The Environment

Publications, presentations and other activities
Evaluation of low-cloud climate feedback through Single-Column Model equilibrium states
2015
by S. Dal Gesso (KNMI), A.P. Siebesma (KNMI), S.R. de Roode (TU Delft),

Equilibrium states of stratocumulus are evaluated for a range of free tropospheric conditions
in a mixed-layer model framework using a number of different entrainment formulations.
The equilibrium states show that a reduced lower tropospheric stability (LTS) and a drier free
troposphere support a thicker cloud layer. Furthermore, cooler and drier free-tropospheric
conditions promote decoupling which is the first stage of stratocumulus break-up into
cumulus. The qualitative results hold for all the considered entrainment formulations,
although the precise quantitative details of the boundary-layer state do vary with the choice
of entrainment parametrization. Perturbations of the equilibrium states by increasing the
sea-surface temperature while keeping the LTS and the free-tropospheric relative humidity
constant leads to cloud thinning and an increased occurrence of decoupling regime. These
results are in line with recent large-eddy simulation studies and increase the confidence in
them by showing their validity for a large range of free tropospheric conditions.

Bibliographic data
Dal Gesso, S., A.P. Siebesma and S.R. de Roode, Evaluation of low-cloud climate feedback through Single-Column Model equilibrium states
Quart. J. Royal Meteor. Soc., 2015, 141, 819-832, doi:10.1002/qj.2398.
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