Abstract

Clouds are primary modulators of Earth's energy balance, in both short and longwave parts of the energy spectrum. It is thus important to understand the links connecting variabilities in cloudiness to variabilities in other state variables of the climate system, and also describe how these links would change in a changing climate. A conceptual model of planetary cloudiness can help elucidate these points. In this work we derive simple representations of cloudiness, that can be useful in creating a theory of planetary cloudi-ness. These representations illustrate how both spatial and temporal variability of cloudi-ness over the whole planet can be expressed in terms of basic state variables. Specifically, cloud albedo is captured by a nonlinear combination of pressure velocity and a measure of the temperature inversion, and cloud longwave effect is captured by surface temperature , pressure velocity, and standard deviation of pressure velocity. From these predic-tors, qualitative links may be drawn between equator-to-pole temperature gradients and cloudiness, which are relevant for an energy balance model. We conclude with a short discussion on the usefulness of this work in the context of global warming response studies .