Clouds are primary modulators of Earth's energy balance. 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 global cloudiness can help elucidate these points. In this work we derive simple representations of cloudiness, that can be useful in creating a theory of global cloudiness. These representations illustrate how both spatial and temporal variability of cloudiness 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 low-level stability, and cloud longwave effect is captured by surface temperature, pressure velocity, and standard deviation of pressure velocity. We conclude with a short discussion on the usefulness of this work in the context of global warming response studies.

The properties of Earth’s albedo and its symmetries are analyzed using twenty years of space-based Energy Balanced And Filled product of Clouds and the Earth’s Radiant Energy System measurements. Despite surface asymmetries, top of the atmosphere temporally & hemispherically averaged albedo appears symmetric over Northern/Southern hemispheres. This is confirmed with the use of surrogate time-series, which fails to refute the hypothesis that the hemispheric albedo difference is distinguishable from zero. An analysis of reflected irradiance time-series fails to find any indicators of some dynamics enforcing this albedo symmetry. This analysis shows that variability in the reflected solar irradiance is almost entirely (99%) due to the seasonal (yearly and half yearly cycle) variations, mostly due to seasonal variations in insolation. Hemispheric residuals of the de-seasonalized reflected solar irradiance are not only small, but indistinguishable from noise, and thus not correlated across hemispheres. The residuals contain a global trend that is large, as compared to expected albedo feedbacks, and is also hemispherically symmetric. Neither the magnitude of these trends nor its symmetry – which could be indicative of a symmetry preserving cloud dynamics – is well understood. To pinpoint precisely which parts of the Earth system establish the hemispheric symmetry, we create an energetically consistent cloud-albedo field from the data. We show that the surface albedo asymmetry is compensated by asymmetries between clouds over extra-tropical oceans, with southern hemispheric storm-tracks being 11% cloudier than their northern hemisphere counterparts.