Wavelike Structures in the Turbulent Layer during the Morning Development of Convection at Dome C, Antarctica

In the period January-February 2014, observations were made at the Concordia station, Dome C, Antarctica to study atmospheric turbulence in the boundary layer using a high-resolution sodar. The turbulence structure was observed beginning from the lowest heightofabout2m,withaverticalresolutionoflessthan2m.Typicalpatternsofthediurnal evolution of the spatio-temporal structure of turbulence detected by the sodar are analyzed. Here, we focus on the wavelike processes observed within the transition period from stable tounstablestratificationoccurringinthemorninghours.Thankstothehigh-resolutionsodar measurements during the development of the convection near the surface, clear undulations were detected inthe overlying turbulentlayer fora significantpartof the time. Thewavelike pattern exhibits a regular braid structure, with undulations associated with internal gravity wavesattributedtoKelvin-Helmholtzshearinstability.Themainspatialandtemporalscales of the wavelike structures were determined, with predominant periodicity of the observed wavypatternsestimatedtobe40-50s.ThehorizontalscalesroughlyestimatedusingTaylor's frozen turbulence hypothesis are about 250-350 m.