Abstract
Abstract. Mesospheric data were analyzed by a composite method combining phase and group velocity tracing technique and the spectra method of Stokes parameter analysis to obtain the propagation parameters of atmospheric gravity waves (AGW) in the height ranges between 63.6 and 99.3 km, observed using the MU radar at Shigaraki in Japan in the months of November and July in the years 1986, 1988 and 1989. The data of waves with downward phase velocity and the data of waves with upward phase velocity were independently treated. First, the vertical phase velocity and vertical group velocity as well as the characteristic wave period for each wave packet were obtained by phase and group velocity tracing technique. Then its horizontal wavelength, intrinsic wave period and horizontal group velocity were obtained by the dispersion relation. The intrinsic frequency and azimuth of wave vector of each wave packet were checked by Stokes parameters analysis. The results showed that the waves with intrinsic periods in the range 30 min–4.5 h had horizontal wavelength ranging from 25 to 240 km, vertical wavelength from 2.5 to 12 km, and horizontal group velocities from 15 to 60 m s−1. Both upward moving wave packets and downward moving wave packets had horizontal group velocities mostly directed in the sector between directions NNE (north-north-east) and SEE in the month of November, and mostly in the sector between directions NW and SWS in the month of July. Comparing with mean wind directions, the gravity waves appeared to be more likely to propagate along with mean wind than against it. This apparent prevalence for downstream wave packets was found to be caused by a systematic filtering effect existing in the process of phase and group velocity tracing analysis: A significant portion of upstream wave packets might have been Doppler shifted out of the vertical range in phase and group velocity tracing analysis.
Highlights
If |φk − φh| < 90◦, there exist two downstream solutions; on the other hand, if 90◦ < |φk − φh| < 180◦, there are two upstream solutions. By this inversion procedure for mid-frequency waves, we have calculated ω, kh, and φk from the measurement values of σ, vpz, and vgz of 364 wave events observed by east–west beam, and have compared outcomes with the corresponding www.ann-geophys.net/31/845/2013/
As long as the inversion solution exists, the corresponding solution obtained by optimization procedure always exists with its cost function S smaller than 0.04, and these two solutions are consistent with each other within only a few percentage of difference; on the contrary, if the solution obtained by optimization procedure has a cost function larger than 0.06, the corresponding inversion solution never exists
Inversion for medium frequency wave approximation is valid only if the measurement errors are sufficiently small
Summary
Azimuth of wave vector of each wave packet were checked of both upward propagating waves and downward propagatby Stokes parameters analysis. This apparent prevalence for But because data of upward propagating waves and downdownstream wave packets was found to be caused by a sys- ward propagating waves were not separately treated, no contematic filtering effect existing in the procHessyodfrpohlaosegayndandsistent pattern of horizontal propaHgaytiodnrdoirloecgtioyn aconudld be group velocity tracing analysis: stream wave packets might have. Lue et al.: Studies of gravity wave propagation in the mesosphere observed by MU radar technique (Kuo et al, 1998, 2007, 2008, 2009) and spectral method of Stokes parameters analysis (Vincent and Fritts, 1987; Eckermann and Vincent, 1989).
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