Evaluation of low-cloud climate feedback through Single-Column Model equilibrium states

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.