A spectral climatology of planetary waves and tidal variability

Four and a half years of data from a meteor radar based at Sheffield, UK, r epresenting measurements of neutral wind velocity in the meteor region abov e 53 degrees 27'N, 3 degrees 53/W, are analysed to produce climatologies of both longer-period (2-30 days) neutral-wind oscillations (e.g. planetary w aves) and longer-period variability in tidal amplitude measurements using r unning (dynamic) periodograms. The observed burst-like nature of longer-per iod oscillations and migration of period are discussed in the light of curr ent planetary-wave theory. Evidence for the cyclical modulation of tidal am plitude with periods similar to those of planetary waves is also presented and its possible origin discussed. (C) 2001 Elsevier Science Ltd. All right s reserved.