Abstract
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 height of about 2 m, with a vertical resolution of less than 2 m. Typical patterns of the diurnal 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 to unstable stratification occurring in the morning hours. Thanks to the high-resolution sodar measurements during the development of the convection near the surface, clear undulations were detected in the overlying turbulent layer for a significant part of the time. The wavelike pattern exhibits a regular braid structure, with undulations associated with internal gravity waves attributed to Kelvin–Helmholtz shear instability. The main spatial and temporal scales of the wavelike structures were determined, with predominant periodicity of the observed wavy patterns estimated to be 40–50 s. The horizontal scales roughly estimated using Taylor’s frozen turbulence hypothesis are about 250–350 m.
Highlights
Experimental investigation of internal shear-induced waves due to a Kelvin-Helmholtz (KH) instability is an important problem in the study and parametrization of the stably-stratifiedItaly 2 A.M
During the sodar measurements at Dome Charlie (Dome C), observations of the smoke flow from the chimney of the Concordia power station sometimes showed a wavelike pattern (Fig. 1) similar to that shown by the sodar
Concordia station is located at Dome Charlie (Dome C), Antarctic plateau, 900 km inland from the nearest coast (75◦06 S, 123◦21 E, 3233 m a.s.l.) with a surface slope ≈ 0.1%
Summary
Experimental investigation of internal shear-induced waves due to a Kelvin-Helmholtz (KH) instability is an important problem in the study and parametrization of the stably-stratified. The internal structure of an inversion layer capping a convective ABL was observed by Browning (1971), Browning et al (1973a) and Readings et al (1973) using pulsed Doppler radar, tethered balloon and radiosonde ascents. The climatological data on the occurrence of wavelike structures observed with conventional sodars are not very accurate, since these measurement systems are unable to detect the fine shortlived wavelike turbulent patterns with periods of a few tens of seconds This leads to the underestimation of the role of the wave processes in the energy transfer in the lower ABL. We analyze the characteristics of wavelike structures within an overlying turbulent inversion layer observed by sodar during the morning development of convection near the surface at Dome C in summer January-February 2014.
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