A study of motions in the winter mesosphere using the partial reflection drift technique

Intensive partial reflection drift observations were made at Adelaide (35°S) for a seven day period in June 1973. The results have been analysed to isolate the prevailing motion and oscillations of various time scales: planetary, 24 hr, 12 hr and gravity waves. Each is discussed in turn with particular emphasis on the variability of energy from day to day and as a function of height. Evidence is presented for the local generation of planetary waves, the presence of the evanescent S_?2¹ mode in the 24 hr oscillation, the influence of the S₄² mode in the 12 hr oscillation and a definite polarization of gravity waves. The energies of all the forms of motion are shown to decay exponentially with increasing height and the deposition of energy and momentum in the upper mesosphere and lower thermosphere is discussed.