VARIATIONS IN THE AMPLITUDE OF SEMIDIURNAL ZONAL TIDE IN THE LOWER THERMOSPHERE AT MIDLATITUDES

G. V. Vergasova and E. S. Kazimirovskii

The variability of zonal semidiurnal tide in the upper mesosphere-lower thermosphere is studied from a bulk of statistical material (1982-1994) from the data of two longitudinally spaced and latitudinally close observatories at Badary (Eastern Siberia) and Kollm (Central Europe). It is found that the spectrum of oscillations varies substantially from month to month, from season to season, and from year to year. The differences in quasiperiodic variations in the amplitudes of semidiurnal zonal tide at Kollm and Badary are related to the climatic features of the regions considered. The calculation results were indicative of the available interseasonal oscillations in the lower thermosphere over midlatitudes. A quasibiennial periodicity is established in amplitude variations.

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