A numerical study of the interaction between stratocumulus and the air overlying it

We have developed a simple, one-dimensional model of the air in the lower free troposphere as it subsides to the stratocumulus cloud deck. First, we fixed the mixed layer in order to determine how the thermodynamic structure of the overlying air impacts the cloud. Our model shows that this overlying air can have a large impact on the net longwave flux across the cloud top and thus the longwave cloud-top cooling. The overlying air, which may require days to subside through a couple of kilometers, undergoes cooling at a rate that depends on its vapor content. The total cooling is thus strongly dependent on the large-scale divergence. This cooling is greatest immediately above the cloud top and can substantially change the strength of the inversion and the potential for a buoyancy reversal upon entrainment. We then coupled this model of the overlying air to a mixed-layer model. -from Authors