Atmospheric Mesostructure and Clear Air Turbulence

Atmospheric Mesostructure and Clear Air Turbulence

Author: Gary J. Thompson

Publisher:

Published: 1973

Total Pages: 32

ISBN-13:

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The mesoscale atmospheric structure in and around regions of clear air turbulence (CAT) is investigated. It is shown that the formation and dissipation of clear air turbulence at several different altitudes is closely related to changes in the atmospheric mesostructure. The turbulence is located in the region of two sloping boroclinic zones and can be attributed to Kelvin-Helmholtz instability resulting from strong wind directional oscillations between these two stable layers. The meteorological sounding data reveal that the lower stable layer and the layer of strong directional oscillations undergo significant upward vertical displacement. The change in turbulence activity can be directly correlated with this motion, and the breakdown of the turbulence and the double stability structure occur almost simultaneously. (Author).


Turbulence in the Free Atmosphere

Turbulence in the Free Atmosphere

Author: N. Vinnichenko

Publisher: Springer Science & Business Media

Published: 2013-11-11

Total Pages: 318

ISBN-13: 1475701004

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Turbulence-the randomly disordered movement of volumes of air of widely varying size-is one of the characteristic features of atmospheric air flows; its investigation is essential for the solution of several theoretical and practical problems. Until recently, owing to experimental difficulties, research on turbu lence was confmed mainly to the lower half of the troposphere. Theoretical investigations have consequently been based on these data. The rapid development of high-altitude aviation and cases of aircraft encoun tering hazardous turbulence led to a sharp intensification of research on turbu lence in the atmosphere up to 10-12 km, and subsequently at greater altitudes. Such research was confined initially to the characterization of the frequency of occurrence of gusts of different speeds, their relation to altitude, geographical conditions, time of day and year, and so on. At the end of the fifties, when the required measuring equipment and experimental techniques had been developed, it became possible to investigate the complete statistical characteristics of turbu lence: the spectral densities of the velocity fluctuations of air flows, structure functions, etc. These data stimulated the further development of theory related to the specific conditions of the free atmosphere.


The Nature of the Mesoscale Wind and Temperature Structure During a Case of CAT

The Nature of the Mesoscale Wind and Temperature Structure During a Case of CAT

Author: Gary J. Thompson

Publisher:

Published: 1973

Total Pages: 28

ISBN-13:

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An examination of the atmospheric mesostructure in regions of clear air turbulence by means of a special network of radiosondes revealed further evidence that Kelvin-Helmholtz (K-H) instabilities may be responsible for the formation of CAT. Significant CAT was encountered in the region of a relatively weak jet maximum. Rapid shear intensification occurred in this region, however, as the result of the development of large wind direction oscillations. A baroclinic zone was observed to form prior to and at the same level as the strongest turbulence. (Author).