The main subjects of this session are the nature, theory and parameterisation of geophysical turbulence and boundary-layer processes relevant to the physics and modelling of weather, climate and air/water-quality. A principal progress in this area of research is needed to more realistically reproduce extreme and dangerous weather events and local consequences of climate change. The session covers the following main topics.

•Theoretical and experimental studies of turbulence-closure problem with emphasis on very stable stratification and turbulent convection, accounting for interactions between the mean flow, turbulence, internal waves and large-scale self-organised structures.
•Large-eddy simulation and direct numerical simulation of turbulent flows.
•Theory and modelling of boundary-layer type flows, such as katabatic winds, internal boundary layers, etc., and parameterisation of sub-grid scale motions in general circulation models (GCMs).
•Methods for calculation of near-surface turbulent fluxes in GCMs; their experimental verification, comparison, and testing; modern demands and prospects for their improvement over land (accounting for vegetation, urban canopy, dust or snow, etc.) and over water.
•Boundary-layer clouds and marine, cloud-topped boundary layers: physics and parameterisation within GCMs.
•Atmospheric boundary layers over heterogeneous terrains: flux-aggregation problems.
.Weather and climate phenomena essentially dependent on the interactions between the atmosphere and underlying land/sea/ice surface