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Ann. Geophys., 19, 883-888, 2001
www.ann-geophys.net/19/883/2001/
© European Geosciences Union 2001
Anisotropy of Doppler spectral parameters in the VHF radar observations at MU and White Sands
G. D. Nastrom1,* and T. Tsuda1
1Radio Science Center for Space and Atmosphere, Kyoto University, Kyoto 611, Japan
*Permanent address: Department of Earth Sciences, St. Cloud State University, St. Cloud, MN 56379, USA
Abstract. Significant differences
are found between the mean spectral widths from beams in the meridional plane
and in the zonal plane at both the MU and the White Sands VHF radars. The
spectral width in the beam directed perpendicular to the prevailing wind is
greater than that in the beam parallel to the wind. The magnitudes of the
differences in spectral width show a linear relationship with wind speed, with
the greatest differences at the greatest wind speeds. The differences in
spectral width show a positive correlation with the differences in
backscattered power. The anisotropy in backscattered power is well-known and is
usually attributed to aspect sensitivity effects. However, the anisotropy in
spectral width does not appear to be due to the same mechanism, and while
several hypotheses to account for this are considered, including finite
range-volume effects, effects from the tilting of isentropic layers, and
anisotropic turbulence effects, it is seen that each of these suggestions has
its shortcomings.
Key words. Meteorology and
atmospheric dynamics (turbulence; instruments and techniques)
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