Direct Numerical Simulation of the Observed Radiative Antarctic Boundary Layer

Recent observations at Dome C, Antarctica, show that the stable boundary layer has a strong dependence on the near-surface wind speed. Under moderate winds, the stable boundary layer extends up to 100 meters and the near-surface temperature inversion is limited. However, under weak winds, the boundary layer may become 10 meters thick or less. In such a case, the surface temperature may be 25 Kelvin colder than the air above 10 meters. This regime, in particular, poses a challenge for state-of-the-art Large-Eddy Simulation and Numerical Weather Prediction models as turbulence becomes weak and restricted to this thin layer. As a result, their results can become heavily influenced by their respective turbulence parametrizations. Therefore, we opt for a novel approach. Direct Numerical Simulations (DNSs), which typically solve turbulence up to the smallest scales, are combined with a simplified atmospheric radiation scheme. In addition to turbulent heat transfer, it is expected that radiative energy transfer and heating by subsidence become equally important in the very stable regime. The simulated cases are based on two observed cases during the Antarctic winter. Intercomparison between the observations and simulations is achieved through non-dimensionalization. This enables us to gain valuable insight regarding the relative importance of these processes, and global intermittency of turbulence in the boundary layer.