THE BIENNIAL WIND AND TEMPERATURE OSCILLATIONS OF THE EQUATORIAL STRATOSPHERE AND THEIR POSSIBLE EXTENSION TO HIGHER LATITUDES

Abstract

In equatorial latitudes, during the past decade, a pronounced oscillation in the zonal wind of approximately 26-month period has been noted at pressure surfaces of 25 and 50 mb. The oscillation decreases in amplitude downward and becomes almost undetectable at 100 mb. While this oscillation appears to be in phase at all longitudes, there is an obvious variation in phase with height with the maximum westerly winds occurring about 4 months earlier at 25 mb. than at 50 mb. and 5 to 6 months earlier at 50 mb. than at 100 mb. There is also good evidence for a latitudinal phase lag in the Tropics with the maximum westerly wind at these levels occurring about 6 months earlier at 30° N. than at the equator. There is a suggestion that this approximately biennial oscillation can be traced through the temperate latitudes of the United States and is first to be noted between latitudes 40° and 50° N., from whence the oscillation propagates northward and southward. Near the equator at these levels the biennial temperature maximum occurs about 3 months prior to the biennial west wind maximum, but from 25° to 35° X., at 25 and 50 mb., the maximum temperature is almost exactly out of phase with the maximum west wind, whereas at 100 mb. the two biennial oscillations are nearly in phase.