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  • Author or Editor: Earl E. Gossard x
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Earl E. Gossard

Abstract

Two theoretical models of shear layers in the atmosphere are examined. The conditions for their dynamic stability are found and their predictions of wavelength to layer-thickness ratio are compared with classical models and with available observational data. Although the models are only rigorously applicable to in-compressible fluids, it is suggested that they also represent conditions in the atmosphere, and clear-air returns published by Katz from the high-power pulse radar at Wallops Island are especially emphasized. Model 2 appears to be able to account for the narrow band characteristic of many of the observed events and also to explain better than other models the observed wavelength to layer-thickness ratios.

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Earl E. Gossard

Abstract

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Earl E. Gossard
and
William R. Moninger

Abstract

The dynamic instability and the kinematics of a multi-layer, shear model of a convective boundary layer are analyzed. Important features of the model include a capping temperature inversion that may or may not be accompanied by a wind discontinuity, a surface-based superadiabatic layer, and a statically stable upper atmosphere. It is shown that the capping inversion can result in a relatively narrow band of dynamically unstable wavenumbers that depend on shear layer thickness, implying a strong selection of scale in growing disturbances. The influence of the various model parameters on selection of the “most unstable” scales is shown and their corresponding propagation velocities are calculated.

A simple form of the model is also used to examine the characteristics of the convectively unstable modes. It is found that two-dimensional disturbances aligned transverse to the wind shear are most dynamically unstable, whereas two-dimensional disturbances parallel to the wind shear are most convectively unstable.

The vorticity and general kinematics of the disturbances are affected in an important way by the presence of a critical level within the height range occupied by the disturbance.

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Willilam R. Moninger
and
Earl E. Gossard

Abstract

A model having smooth wind and density profiles, for which a new solution of the Taylor-Goldstein equation can be found, is described. This model is particularly suitable for comparison with the analogous piecewise linear model so that the influence of “corners” in profiles can be judged. Such corners are found in models studied by Rayleigh, Goldstein, Taylor, Howard, Holmboe, and Gossard.

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