Some characteristics of turbulence from summertime measurements over an Antarctic ice sheet

Measurements of turbulence were made by fast response instrumentation over an Antarctic ice sheet during the austral summer. Turbulent fluxes of momentum, heat and water vapour were determined by the eddy correlation method. Dairy cycle of some relevant turbulence quantities were investigated to determine the mean seasonal characteristics of the atmospheric boundary layer. It is prevalently stably stratified, averaged heat flux is always negative and latent heat flux is positive but exchange processes are of limited extent being mostly inhibited by the low level of turbulence. Relevant deviations from this behaviour were observed during katabatic wind episodes and free convection events. In the first case it is observed that boundary layer stratification tends to become more neutral, temperature as well downward heat and upward water vapour fluxes increase notably and energy is stored inside the snow. Unstable thermal stratification occurs only in 15% of cases, it is concentrated in the central hours of the day and often a rapid transition to free convection is observed. Sporadic cases were also observed in late evening and early morning hours.