Article ID: 2021-062
We analyse a multi-model ensemble at convection-resolving resolution based on the DYAMOND models, and a resolution ensemble based on the limited area model COSMO over 40 days to study how tropical and subtropical marine low clouds are represented at kilometer-scale resolution.
The analysed simulations produce low cloud fields that look in general realistic in comparison to satellite images. The evaluation of the radiative balance, however, reveals substantial inter-model differences and an underestimated low cloud cover in most models. Models that simulate increased low cloud cover are found to have a deeper marine boundary layer (MBL), stronger entrainment, and an enhanced latent heat flux. These findings demonstrate that some of the fundamental relations of the MBL are systematically represented by the model ensemble which implies that the relevant dynamical processes start to become resolved on the model grid at kilometer-scale resolution. A sensitivity experiment with the COSMO model suggests that differences in the strength of turbulent vertical mixing may contribute to the inter-model spread in cloud cover.