Earth’s Observed Hemispheric Albedo Symmetry by Cloud Type: Climatology, Trends, and Tests of Cloud Adjustment Hypotheses | CU Experts

Earth’s Northern and Southern Hemispheres reflect identical amounts of; sunlight. How — and whether — this hemispheric albedo symmetry is; maintained remains a mystery. We decompose Earth’s hemispheric albedo; symmetry into components associated with different cloud types as; defined by cloud effective pressure and optical thickness. Greater; reflection by the surface, clear-sky atmosphere, and high clouds in the; Northern Hemisphere is balanced by low and mid clouds (dominated by; stratocumulus) in the Southern Hemisphere. Both hemispheres have; darkened by ~0.5-0.8 W/m2/decade due to decreasing low; and mid cloud and surface reflection, partially offset by increasing; high cloud reflection. Cloud reflection trends largely follow cloud; fraction, with the exception of decreasing stratocumulus albedo in both; hemispheres. Hypotheses that all-sky symmetry is maintained despite; clear-sky changes via adjustments in high clouds within the; Intertropical Convergence Zone or in low and mid clouds in the Southern; Ocean are not supported at interannual or decadal timescales.

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