Earth’s Albedo and Its Symmetry

Abstract 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 reflected solar irradiance appears symmetric over Northern/Southern hemispheres. This is confirmed with the use of surrogate time‐series, which provides margins of for possible hemispheric differences supported by Clouds and Earth's Radiant System data. time‐series are further analyzed by decomposition into a seasonal (yearly and half yearly) cycle and residuals. Variability in the reflected solar irradiance is almost entirely (99%) due to the seasonal variations, mostly due to seasonal variations in insolation. The residuals of hemispherically averaged are not only small, but also indistinguishable from noise, and thus not correlated across hemispheres. This makes yearly and sub‐yearly timescales unlikely as the basis for a symmetry‐establishing mechanism. The residuals however contain a global trend that is large, as compared to expected albedo feedbacks. It is also hemispherically symmetric, and thus indicates the possibility of a symmetry enforcing mechanism at longer timescales. 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. This again indicates that, assuming the albedo symmetry is not a result of chance, its mechanism likely operates on large temporal and spatial scales.