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Ann. Geophys., 25, 77-86, 2007
www.ann-geophys.net/25/77/2007/
© European Geosciences Union 2007
Phase and group velocity tracing analysis of projected wave packet motion along oblique radar beams – qualitative analysis of QP echoes
F. S. Kuo1, H. Y. Lue2, and C. L. Fern3
1Department of Electro-Optical Engineering, Van Nung University, Chung-Li, Taiwan
2Department of Physics, Fu-Jen Catholic University, Hsin-Chuang, Taiwan
3General Education Center, National Yunlin University of Science and Technology, Touliu, Yunlin, Taiwan
Abstract. The wave packets of atmospheric gravity waves were numerically generated, with a given characteristic wave
period, horizontal wave length and projection mean wind along the horizontal
wave vector. Their projection phase and group
velocities along the oblique radar beam (vpr and vgr), with
different zenith angle θ and azimuth angle φ, were analyzed by
the method of phase- and group-velocity tracing. The results were
consistent with the theoretical calculations derived by the dispersion
relation, reconfirming the accuracy of the method of analysis. The RTI plot
of the numerical wave packets were similar to the striation patterns of the QP
echoes from the FAI irregularity region. We propose that the striation range
rate of the QP echo is equal to the radial phase velocity vpr, and the slope
of the energy line across the neighboring striations is equal to the radial
group velocity vgr of the wave packet; the horizontal distance between
two neighboring striations is equal to the characteristic wave period τ.
Then, one can inversely calculate all the properties of the gravity wave
responsible for the appearance of the QP echoes. We found that the possibility
of some QP echoes being generated by the gravity waves originated from lower
altitudes cannot be ruled out.
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