The semidiurnal tide in the lower thermosphere

Abstract

The time variation of winds was measured from trails of chemiluminescent vapor throughout the night of December 3, 1962, in the northern hemisphere at Eglin Air Force Base, Florida, 29°N [Rosenberg and Justus, 1966]. They found the sinusoidal variation of both the north-south and the east-west wind profiles above 100 km to be characterized by a downward variation of phase velocity consistent with a periodicity of approximately 12 hours. Although my basic concern in this note is the reality of the midlatitude semidiurnal tide at these heights during winter, as evidenced by comparison with radio meteor winds determined in the southern hemisphere month of June 1961 at Adelaide, 35°S [Roper and Elford, 1965a],. it should be emphasized that, as has been shown by Hines [1966], the apparent dominance of a 12-hour component over the limited period of observation does not preclude the existence of an appreciable diurnal tide.