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  • Author or Editor: A. G. Kjelaas x
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A. G. Kjelaas and G. R. Ochs

Abstract

A wind-measuring system using three separate optical systems, each consisting of a 3 mW He-Ne 1aser and two photodiode receivers, forming an equilateral triangle 300 m on a side, has successfully measured the divergence over the area of the triangle, and the space-averaged horizontal wind vector. Good correlation was found between the flow into the triangle and occurrences of thermal plumes seen by an adjacent acoustic sounder. The flow into the triangle was proportional to the vertical velocity. During large convective activity, there was a certain periodicity in the occurrence of plumes.

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D. T. Gjessing, A. G. Kjelaas, and J. Nordø

Abstract

The influence of atmospheric stability on the vertical spectra of refractive index and air velocity is studied.

Spectra of refractive index and air velocity are deduced from beam-swinging experiments in the area between Norway and Denmark where a height interval from some 400 m to some 12 km is involved. These spectra are compared with the results of data obtained from radiosondes.

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A. G. Kjelaas, D. W. Beran, W. H. Hooke, and B. R. Bean

Abstract

Three acoustic sounders, with antennas having vertically-pointed beams located at the vertices of a triangle about 300 m on a side, have been used successfully to calculate horizontal phase velocities of gravity waves in the lowest 1000 m of the atmosphere. The wave parameters obtained were compared with those obtained by an array of micrographs. The results from the two independent techniques agreed well in all cases where the waves were detected by both methods. However, the acoustic-sounder array was also able to detect gravity waves propagating in an inversion overlying the convective boundary layer that were undetected by the microbarograph array because of wave attenuation in the convective region.

Wave-associated vertical-velocity fluctuations inside the undulating structure were measured using Doppler techniques to an accuracy of about ±0.1 m sec−1. Vertical-velocity fluctuations of about ±0.5 m sec−1 were measured inside one wave with displacement amplitude of 120 m and wavelength of 5.5 km. From wave-associated vertical-velocity fluctuations, displacement amplitude and wave period, we could calculate the wind speed component along the wave propagation direction. This calculated wind speed component agreed reasonably well with the value derived independently from radiosonde measurements.

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