Power Spectra of Oblique Velocities in the Troposphere and Lower Stratosphere Observed at Arecibo, Puerto Rico

M. F. Larsen Department of Physics and Astronomy, Clemson University, Clemson, SC 29631

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R. F. Woodman Instituto Geofisico del Peru, Apartado 3747, Lima 100, Peru

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T. Sato Radio Atmospheric Science Center, Kyoto University, Kyoto, Japan

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M. K. Davis School of electrical Engineering, Cornell University, Ithaca, NY 14853

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Abstract

Wind profiles measured with the Arecibo Observatory 430 MHz radar during 1979 and 1980 have been used to calculate frequency and radial wavenumber power spectra. Periods between 2 min and 6 h and vertical wavelength between 300 m and 13.5 km are covered by the spectra The data are line-of-sight velocity components obtained with a beam pointing between 5.4° and 15° off-vertical. The presented evidence supports the conclusion that the dominant contribution to the spectra at periods less than 1 h is from the vertical velocity component. The frequency spectra have spectral slopes near −1 for periods of less than 1 h, and the radial wavenumber spectra have slopes between −1 and −3/2. The results are discussed in the context of two-dimensional turbulence and a universal gravity-wave spectrum. We also present the spectra from an event associated with convection in the early evening hours. A strong peak in the spectral energy near the Brunt-Väisälä frequency was present during the convective activity. The energy content at longer. periods was found to be enhanced in the ensuing period when the convective energy input at shorter time scales new the Brunt-Väisälä period had diminished.

Abstract

Wind profiles measured with the Arecibo Observatory 430 MHz radar during 1979 and 1980 have been used to calculate frequency and radial wavenumber power spectra. Periods between 2 min and 6 h and vertical wavelength between 300 m and 13.5 km are covered by the spectra The data are line-of-sight velocity components obtained with a beam pointing between 5.4° and 15° off-vertical. The presented evidence supports the conclusion that the dominant contribution to the spectra at periods less than 1 h is from the vertical velocity component. The frequency spectra have spectral slopes near −1 for periods of less than 1 h, and the radial wavenumber spectra have slopes between −1 and −3/2. The results are discussed in the context of two-dimensional turbulence and a universal gravity-wave spectrum. We also present the spectra from an event associated with convection in the early evening hours. A strong peak in the spectral energy near the Brunt-Väisälä frequency was present during the convective activity. The energy content at longer. periods was found to be enhanced in the ensuing period when the convective energy input at shorter time scales new the Brunt-Väisälä period had diminished.

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