Earth Planets Space, Vol. 51 (Nos. 7, 8), pp. 711-717, 1999
Yu. I. Portnyagin1, E. G. Merzlyakov1, Ch. Jacobi2, N. J. Mitchell3, H. G. Muller4, A. H. Manson5, W. Singer6, P. Hoffmann6, and A. N. Fachrutdinova7
1Institute for Experimental Meteorology, Obninsk, Russia
2Institute for Meteorology, University of Leipzig, Germany
3Department of Physics, University of Wales, Aberystwyth, U.K.
4Cranfield University, RMCS Shrivenham, Swindon, U.K.
5Institute for Space and Atmospheric Studies University of Saskatchewan,, Saskatoon, Canada
6Institute of Atmospheric Physics, Kuehlungsborn, Germany
7Kazan State University, Kazan, Russia
(Received July 28, 1998; Revised February 8, 1999; Accepted April 20, 1999)
Abstract: Technique appropriate to the analysis of lower thermospheric wind data recorded by global-scale networks of ground-based instruments are discussed. The S-transform technique is shown to be effective in the analysis of the main features of travelling planetary waves and this method is applied to the time series of horizontal-velocity data obtained during the DYANA campaign (January-March, 1990). The analysis reveals strongly transient behavior of the day-to-day lower thermosphere wind variations, as well as their specific longitudinal structure. In particular, it was found that the revealed quasi-15 day and quasi-5 day wind oscillations may be described as transient westward-propagating waves with zonal wavenumber s=1, while an oscillation with the a period near 7 days is tentatively identified as having a wavenumber s=0.