Sodar investigations of Kelvin-Helmholtz waves in low-level jets

The structure and dynamic characteristics of the Kelvin-Helmholtz billows (KHB), observed with a sodar
in the stable atmospheric boundary layer, are studied by means of composite analysis, which consists in the
averaging of samples selected according to certain criteria. Using a specific kind of this method allowed the
authors to obtain the fine structure of the perturbation velocity fields from the sodar data. The events of most
pronounced KHB were visually selected from echograms of continuous sodar measurements in the Moscow
region over 2008-2016. The composite patterns of KHB have been constructed for a few cases of clear inclined-
stripes echogram patterns to derive a typical finescale structure of billows and a spatial distribution of wind
speed and shear within them. The interconnection between echo intensity and wind shear variations within such
patterns is shown. The typical distributions of velocity perturbation within various forms of billows are found.