Clouds are a major challenge for climate science, and their effects are difficult to quantify precisely. Clouds interfere with atmospheric radiation. They scatter sunlight back into space and thus prevent the Earth from warming up. But clouds also hold back thermal radiation upwelling from the surface. The two effects usually cancel each other out to some extent, resulting in a net cloud radiative effect, the magnitude of which depends on the cloud type, the environment, and various cloud micro- and macrophysical properties. However, their detailed numerical representation becomes a challenge because cloud formation processes occur in a wide range of spatial and temporal scales. Moreover, aerosol can affect clouds in various ways. Beside the microphysical impact of aerosol particles on droplet nucleation and ice formation, the interference of aerosol with atmospheric radiation leads potentially to changes in local heating, surface fluxes and thus mesoscale circulations, all of which may also modify clouds.

The research presented in the talk focuses on disentangling the complex intertwining of cloud and aerosol effects with atmospheric radiation and dynamics. Methods and models are applied that span a wide range of scales. A general overview of the approaches will be given. Additionally, the representation of cloud properties and radiative effects in the ICON model, on local aerosol-mediated cloud adjustments over land and on the climate impacts of the extreme Australian wildfires will be discussed in detail. As a perspective, new technical possibilities in cloud modelling through improved parallelization concepts and machine-learning methods will be discussed.