Cloud Decoupling of the Surface and Planetary Radiative Budgets

Abstract

We employ a one-dimensional radiative-convective equilibrium model with multiple cloud layers to demonstrate that the surface equilibrium temperature is highly sensitive to the vertical distribution of effective cloud base heights. It is also demonstrated that the reflected solar flux from an ensemble of cloud layers is independent of the vertical distribution of these cloud layers and is a function only of the total water path integrated in the vertical, a property which also determines the solar radiation reaching the surface. The downward longwave radiation, on the other hand, depends strongly on the effective cloud base height as well as the background water vapor distribution. It is argued that the longwave radiative transfer processes of cloud tend to decouple the radiative budgets at the top of the atmosphere and the surface. Thus, for a given total atmospheric optical thickness, it is possible to obtain different values of surface temperature under conditions of radiative equilibrium at the top of the atmosphere.