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  • Author or Editor: Earl E. Gossard x
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Earl E. Gossard
and
A. Shelby Frisch

Abstract

The relationship between the variances of temperature and vertical velocity fluctuations is examined experimentally and theoretically. Comparison of the variance data and the mean gradient data recorded on the 300 m tower at the Boulder Atmospheric Observatory leads to the conclusion that the remotely sensed ratio of the temperature and velocity variances offers hope of measuring gradients of temperature and radar refractive index from ground-based acoustic or radar clear-air sounders. Relationships in which temperature gradient depends only on the ratio of the variances of temperature and vertical velocity are found both from the flux equation and from the energy budget/temperature variance equations. From the two independent relations, a theoretical expression for Prandtl number versus Richardson number is found for a limited range of Richardson numbers. Finally, the character and magnitude of the influence of the stress and conductivity terms are estimated from the linearized problem, and solutions are found in terms of eddy viscosity and conductivity.

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Earl E. Gossard
and
Richard G. Strauch

Abstract

When long-wavelength radars are used to observe the atmosphere, there are occasions when radar return from a volume of cloud is unexpectedly large relative to that predicted by the classical incoherent scatter from individual cloud droplets. The assumption of incoherence predicts the scattered power to be proportional to the inverse fourth power of the wavelength. The observed weaker wavelength dependence could result from Bragg-coherent scatter from the ensemble of droplets or it could result from an enhancement by the cloud of inhomogeneities in the dielectric constant of the gaseous medium within the cloud. Both mechanisms are discussed and compared with data acquired in a forward-scatter mode by two 3 cm wavelength radars of NOAA's Wave Propagation Laboratory. Observed differences between the in-cloud and out-of-cloud refractive index spectra are discussed and conclusions are suggested.

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Earl E. Gossard
,
Russell B. Chadwick
,
Thomas R. Detman
, and
John Gaynor

Abstract

Radars and acoustic sounding systems sense properties of the turbulence structure of the atmosphere. If atmospheric turbulence can be related to the mean gradient parameters, Doppler radars and acoustic sounders can provide information about height profiles of quantities such as temperature and refractive index as well as wind in stable regions of the atmosphere. In this paper turbulent and mean quantities were measured on the 300 m meteorological tower at the Boulder Atmospheric Observatory near Erie, Colorado, and the relationships between the turbulent and mean gradient quantities were examined in order to evaluate hypotheses for simplifying the kinetic energy balance and refractive index variance equations. FM-CW radar measurements of backscattered power and Doppler spectral width were also made for comparison with tower-measured refractive index spectra and Doppler velocity spectra. Height distributions of the turbulent dissipation rate within stable layers are shown and viscous cutoff radar wavelengths calculated.

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