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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 6
Ann. Geophys., 15, 813–822, 1997
https://doi.org/10.1007/s00585-997-0813-8
© European Geosciences Union 1997
Ann. Geophys., 15, 813–822, 1997
https://doi.org/10.1007/s00585-997-0813-8
© European Geosciences Union 1997

  30 Jun 1997

30 Jun 1997

Long-period unstable gravity-waves and associated VHF radar echoes

R. M. Worthington and L. Thomas R. M. Worthington and L. Thomas
  • Department of Physics, University of Wales, Aberystwyth, Dyfed, SY23 3BZ, UK

Abstract. VHF atmospheric radar is used to measure the wind velocity and radar echo power related to long-period wind perturbations, including gravity waves, which are observed commonly in the lower stratosphere and tropopause region, and sometimes in the troposphere. These wind structures have been identified previously as either inertia-gravity waves, often associated with jet streams, or mountain waves. At heights of peak wind shear, imbalances are found between the echo powers of a symmetric pair of radar beams, which are expected to be equal. The largest of these power differences are found for conditions of simultaneous high wind shear and high aspect sensitivity. It is suggested that the effect might arise from tilted specular reflectors or anisotropic turbulent scatterers, a result of, for example, Kelvin-Helmholtz instabilities generated by the strong wind shears. This radar power-difference effect could offer information about the onset of saturation in long-period waves, and the formation of thin layers of turbulence.

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