The role of Earth's major cloud systems in the hemispheric albedo symmetry

Abstract

We investigate in depth the role of major cloud systems in the well-known symmetry of albedo or reflected solar radiation (RSR) between the Earth’s Northern and Southern hemispheres which has been shown previously to be quite robust on multi-annual time scales. Here we quantify the degree of symmetry for the entirety of a recent 22-year period, while also analyzing the modulation of its interannual variability by clouds. To achieve this, we employ climatological cloud regimes which we have previously termed “regimes of regimes” or RORs. By pairing RORs with monthly RSR values from the CERES EBAF dataset we elucidate how several large RSR asymmetries at the ROR level, mainly due to ROR hemispheric population contrasts, conspire to produce near-symmetry at the hemispheric level. We also investigate how interannual variations of small deviations from hemispheric RSR symmetry relate to interannual variations of the ROR RSR asymmetries. Finally, we probe the role of the complementary symmetry in absorbed solar radiation (ASR), and specifically of its atmospheric component, in the broader context of hemispheric energetics. Our analysis sheds light on the role of major global cloud systems in modulating the mean state and variability of the equitable contribution of the two hemispheres to the global RSR.