The Composite Shape and Structure of Braid Patterns in Kelvin–Helmholtz Billows Observed with a Sodar

Vasily Lyulyukin A.M. Obukhov Institute of Atmospheric Physics, Moscow, Russia

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Rostislav Kouznetsov A.M. Obukhov Institute of Atmospheric Physics, Moscow, Russia, and Finnish Meteorological Institute, Helsinki, Finland

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Margarita Kallistratova A.M. Obukhov Institute of Atmospheric Physics, Moscow, Russia

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Abstract

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 2008–10. 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.

Corresponding author address: Vasily Lyulyukin, A.M. Obukhov Institute of Atmospheric Physics, Pyzhevsky per. 3, Moscow, 119017 Russia. E-mail: lyulyukin@gmail.com

This article is included in the ISARS 2012 special collection.

Abstract

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 2008–10. 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.

Corresponding author address: Vasily Lyulyukin, A.M. Obukhov Institute of Atmospheric Physics, Pyzhevsky per. 3, Moscow, 119017 Russia. E-mail: lyulyukin@gmail.com

This article is included in the ISARS 2012 special collection.

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