GABLS4: a model inter-comparison study in extremely stable conditions

The 4th inter-comparison case (GABLS4) aims to study: the interaction between the boundary layer and the surface in strong stability and the decrease of the turbulence during the diurnal transition. This exercise is being conducted in collaboration with the GEWEX Panel on Global Atmospheric Study (GASS) and the Global Land Atmosphere System Study (GLASS).

This intercomparison uses observations from the Dome C Research Station on the Antarctic Plateau during the summer. The boundary layer observations with turbulent fluxes and meteorological variables acquired from a 45-m tower are on a homogenous surface such as snow (low conductivity) and on a flat topography. The inter-comparison will consist of 3 inter-comparisons : Single Column Model (SCM), Large Eddy Simulation (LES) and land-snow model (LSM). It is organized in 3 steps. The first one is dedicated to the LSM and the SCM with an interactive surface (snow) scheme. Then, in the second one, the observed surface temperature will be prescribed in the SCM and in the LES models. The third one is an idealized one or simplified one, was designed for a wider LES community or for explicit algebraic turbulence models. After a rapid overview of the setup, we will focus on the SCM results and how the results are sensitive to the surface characteristics and the vertical resolution. In particular, a large variability in surface fluxes was highlighted in all types of simulations with variations about 30W/m2 during daytime and night-time which is about 100% of the ensemble mean value.