The low stratiform cloud model presented here appears as a generalization of Lilly's model (1968). Its main new apsects lie 1) in a detailed vertical computation of the longwave and the shortwave radiative flux profiles and 2) in a formulation of the entrainment rate and the turbulent flux profiles which takes into account the nonlinear vertical structure of the radiative fluxes. Furthermore, the radiative divergence is no longer externally prescribed, like in other models; it is determined as function of the mixed-layer and cloud characteristics. All these features allow a more complete coupling between the turbulent mixing and the radiative fluxes. Within the cloud, the turbulent flux profiles of the moist static energy and the virtual dry static energy are nonlinear functions of height, due to the radiative divergence. This nonlinear structure results in a realistic negative entrainment flux at cloud top. In the sensitivity tests, the stress has been put on the variability of the radiative and turbulent fluxes as functions of the cloud microphysics. The result is that the integrated liquid water content (liquid water path) is the predominant factor in fixing the radiative and turbulent fluxes, with a secondary but non-negligible role played by the drop size distribution. For optically thin clouds where the shortwave absorption is negligible, the infrared cooling is distributed throughout the whole cloud and is highly sensitive to the liquid water path; thus the turbulent fluxes and the entrainment rate also depend strongly on the liquid water path. When increasing the liquid water path, the longwave cooling becomes saturated and localized in a layer of progressively reduced thickness at cloud top. Thus for thick clouds, with no solar flux, our model gives results which are similar to those of Lilly-type models. The solar heating does not saturate as the liquid water path increases. Moreover, since it is distributed throughout the cloud deck, it not only reduces the radiative divergence and the turbulent kinetic energy production at cloud top, but it also acts as a source of this latter energy component near the cloud base. The overall result is a noticeable reduction of the entrainment rate. This suggests a strong diurnal cycle for thick stratocumulus decks.