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Earth's albedo and its symmetry
  • George Datseris,
  • Bjorn Stevens
George Datseris
Max Planck Institute for Meteorology

Corresponding Author:[email protected]

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Bjorn Stevens
Max Planck Institute for Meteorology
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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.