Why is Earth’s albedo hemispherically symmetric despite static asymmetries?

Most planets have an elliptic orbit and non-zero obliquity. Even though Kepler’s 2nd law states that each hemisphere receives the same total amount of sunlight, they do not do so in the same way. Specifically for the Earth, the southern hemisphere has its summer near the sun, receiving more intense sunlight but for less time, with respect to the northern hemisphere. In addition, the surface-to-land ratio between the two hemispheres is different, which has direct impact on the (average) surface albedo value: the northern hemisphere has 10% larger surface albedo. For timescales less than thousands of years, these imbalances are static.
Even though these static imbalances exist, the Earth’s albedo (how much incoming solar radiation is reflected in total, at the top of the atmosphere) displays hemispheric symmetry. The reasons for this are unclear because both imbalances can be assumed to cause asymmetries.

To better understand efefcts of the static asymmetries we suggest for this project to perform and analyze idealized simulations with an aquaplanet configuration of the ICON atmospheric general circulation models where different asymmetries are switched on and off individually at varying strength.

More information is provided here.

Supervisors: George Datseris, Hauke Schmidt, and Bjorn Stevens