The main objective of this session is to discuss the nature, theory and parameterisation of boundary layer processes relevant to weather-prediction, climate and air-pollution modelling. Improved parameterisation of geophysical turbulent boundary layers became a challenging problem in the light of new demands from operational modelling employing very high resolution general circulation models (GCMs), especially the coupled atmosphere-ice-ocean model suites needed to realistically predict local consequences of the climate change. The session will cover the following main topics:

1. New developments in experimental studies and theoretical modelling of turbulent boundary layers in the atmosphere and the ocean
(a) Stable and neutral regimes (role of internal gravity waves)
(b) Convective regimes (role of large-scale semi-organised structures)
(c) Advanced turbulence closure models (achievements, experimental verification, limits of applicability, alternative approaches)

2. Large-eddy simulation of turbulent boundary layers

3. Modelling of boundary-layer type flows (sea breezes, katabatic winds, internal boundary layers, etc.) and parameterisation of the sub-grid scale flows in GCMs

4. Calculation of the near-surface turbulent fluxes: experimental verification, comparison, and testing of schemes currently used in GCMs; modern demands and prospects for improvement
(a) over land (vegetation, urban canopy, dust, snow, etc.)
(b) over water (open ocean, costal waters, storms, swell)

5. Boundary-layer clouds and marine, cloud toped boundary layers within atmospheric GCMs

6. Atmospheric boundary layers over heterogeneous terrain, archipelago and coastal zones: flux aggregation problem

7. Weather and climate phenomena essentially dependent on the interactions between the atmosphere and underlying land/sea/ice surface