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T. J. Herron

Abstract

Atmospheric gravity waves generated by low-altitude nuclear explosions have been detected by ground-level microbarographs and by ionospheric instruments. Group velocity dispersion curves have been computed for propagation over the short and long great-circle paths. Apparent lower velocities over the short paths are interpreted as due to the “rise time” of the nuclear disturbances to ionospheric levels with subsequent generation of gravity waves at those levels. Corrections to the travel times to account for the “rise time” delays are estimated to be ∼13 min or more. Corrected group velocity dispersion curves are found to agree with theoretical group velocity dispersion for atmospheric surface waves.

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I. Tolstoy and T. J. Herron

Abstract

It is shown, given perturbations of the jet stream wind system similar to those reported from balloon and aircraft studies, that it is possible to calculate ground level pressure fluctuations. Using a density stratified model of the troposphere and a constant gravity field, and assuming the jet stream to act as a traveling disturbance, a simple linear model predicts the correct order of magnitude and power spectra for microbarographic fluctuations in the 5–60 min period range.

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I. Tolstoy and T. J. Herron

Abstract

Atmospheric gravity waves excited by nuclear explosions were recorded on several occasions during the period 1967–68, on a large aperture (250 km × 200 km) array of long-period microbarographs (1–60 min period pass-band) in the New York-New jersey area. The spectrum of these waves peaks near a period of 15 min and their average group velocity (∼600 m sec−1), their dispersion and attenuation conform to theoretical predictions, for the surface mode.

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T. J. Herron and I. Tolstoy

Abstract

A major portion of atmospheric pressure fluctuations in the 30–90 min period range was observed to move across a small array of microbarographs with speeds and directions that correlate with jet stream winds. Measured speeds (10–50 m sec−1) and periods, with plane wave assumptions, yield wavelengths of the order of 100 km. The pressure fluctuations were observed, however, to decorrelate in much less than one wavelength, implying that they are not free waves, but more likely are disturbances dragged along by the tropopause winds.

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T. J. Herron and H. Montes

Abstract

The high energy disturbance in the South Pacific on 24 August 1968 generated long-period (10–15 min), high-velocity (600 m sec−1) atmospheric pressure waves observed on a large aperture (250 km) micro-barograph array. A vertical incidence ionospheric Doppler sounder (4.8 MHz), located at the center of the array, detected an ionospheric oscillation (at a height of ∼225 km) in high correlation with the ground-level pressure signal. Correlated ionospheric Doppler-shift and ground-level pressure signals were observed for both the short and long great-circle paths from the test site. The Doppler sounder signal is the result of vertical changes of the ionosphere accompanying the passage of the atmospheric wave which has been identified by Tolstoy and Herron as a surface gravity wave.

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