Turbulence mixing in very stable boundary layer at Dome C

The previous Gewex Atmospheric Boundary Layer Studies model inter-comparison cases highlighted that a better understanding of the boundary layer under stably stratified conditions remains a challenge.

Dome C, (75°S, 123°E, 3233 m asl) in the East Antarctic Plateau is a prefect place to study turbulent mixing in stratified flows and the transition between stable and unstable regimes. The lower boundary layer is continuously monitored since 2009. In summer, the strong surface-based temperature inversion observed at lower solar elevation angles (“night”) gives way to a slighty convective boundary layer during the « day ». The amplitude of the diurnal cycle can reach 18°C whereas the average temperature is about -30°C at the surface. Dome C has been selected for the GABLS4 intercomparison project case (see presentation by Bazile et al. In Boundary layer processes, observations and modeling, including interactions with the land surface and biosphere session.

The present study aims at characterizing turbulence using the statistics on both modelled and measured data. A large eddy simulation is in preparation with the non-hydrostatic atmospheric model Méso-nh coupled with the Surfex surface model. The objective is to reproduce the diurnal cycle, and compare the flow structures developed in the simulation with those observed with high frequency sensors. These sensors are classic meteorological instruments and sonic-anemometers profiling the boundary layer and measuring the temperature and the three components of wind velocity up to 10Hz.

A Large Eddy Simulation performed with a vertical resolution of 1m and an horizontal resolution of 10m is being set up, the results of which will be described as available by the time the conference takes place. The sensitivity studies with single column simulations with Méso-NH set up to optimize the LES configuration will be presented. In particular sensitivity to the surface forcing conditions will be discussed.