Evaluation of Southern Ocean cloud in the HadGEM3 general circulation model and MERRA-2 reanalysis using ship-based observations

Atmospheric Chemistry and Physics (2020)

Southern Ocean shortwave radiation biases are a common problem in contemporary general circulation models.

We use multi-year ship-based observations and the CERES spaceborne radiation budget measurements to contrast cloud representation and shortwave radiation in the atmospheric component Global Atmosphere (GA) version 7.1 of the HadGEM3 GCM and the MERRA-2 reanalysis.

We find that the prevailing bias is negative in GA7.1 and positive in MERRA-2, suggesting that cloud and boundary layer parameterisations are responsible for the bias and that in GA7.1 a major part of the shortwave radiation bias can be explained by cloud cover underestimation, relative to underestimation of cloud albedo.