Solar "shortwave" irradiance is the main source of energy to the surface and the atmosphere. Outgoing thermal "longwave" irradiance and reflected shortwave irradiance is the only energy sink from the atmosphere. Both shortwave and longwave irradiances interact with the surface, clouds and aerosols in complex manners that are not yet comprehensively modelled in weather and climate models. Here, we will address the current state-of-the-art of these interactions, as they are represented in contemporary models. The increasing need for accurate radiation outputs for the growing renewable energy sector will also be addressed. Attention will be paid to the validation of modelled radiation output by using ground-based and satellite measurements of irradiances.

This session is expected to focus on the above points and to gather presentations and posters on the following topics:

• Handling of radiative transfer in clear and cloudy atmospheric boundary layers including three-dimensional radiative transfer aspects.
• Surface-radiation interactions including both general radiative properties of the surface and interactions with complex topographies and canopies.
• Evaluation of radiation and cloud output from NWP models and use of shortwave radiation measurements for cloud verification.
• General aspects of radiation and microphysics parametrizations and their interactions in NWP models
• Obtaining the inherent optical properties of cloud, precipitation and aerosol particles for the use of NWP models
• Time, space and spectral resolution of the radiation parametrizations required by the models from mesoscale to global circulation.