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 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.