Articles | Volume 19, issue 5
31 May 2001
 | 31 May 2001

On the longitudinal structure of the transient day-to-day variation of the semidiurnal tide in the mid-latitude lower thermosphere − I. Winter season

E. G. Merzlyakov, Yu. I. Portnyagin, C. Jacobi, N. J. Mitchell, H. G. Muller, A. H. Manson, A. N. Fachrutdinova, W. Singer, and P. Hoffmann

Abstract. The longitudinal structure of the day-to-day variations of semidiurnal tide amplitudes is analysed based on coordinated mesosphere/lower thermosphere wind measurements at several stations during three winter campaigns. Possible excitation sources of these variations are discussed. Special attention is given to a nonlinear interaction between the semidiurnal tide and the day-to-day mean wind variations. Data processing includes the S-transform analysis which takes into account transient behaviour of secondary waves. It is shown that strong tidal modulations appear during a stratospheric warming and may be caused by aperiodic mean wind variations during this event.

Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides)