Evidence of global-scale waves with zonal wave number zero in the stratosphere

Coherency spectra derived from time series of stratospheric quantities indicate oscillations in the frequency range below 0.5 d^–1 which are correlated on a global scale. Satellite observations of total ozone and stratospheric radiance (BUV and SIRS, Nimbus4, April–November 1970) have been used to derive phase relationships of such oscillations. As an example, an oscillation of total ozone with a period of 7.5 d and zonal wave number zero is analyzed in detail. The basic assumption is made and tested, that the oscillation reflects stratospheric planetary waves as obtained from Laplace's tidal equations. The observed latitudinal phase shifts for the total ozone oscillation are in good agreement with theoretical predictions. It is concluded from the observations of ozone and radiance that mainly divergence effects related to global-scale waves are responsible for the 7.5 d oscillations of total ozone at high and middle latitudes and at the equator whereas in the latitude range 10°S–20°S predominantly temperature effects are important. Meridional wind amplitudes of some 10 cm/s are sufficient to explain the high and mid-latitude ozone oscillations. At low latitudes vertical wind amplitudes of about 0.2 mm/s corresponding to height changes of the ozone layer of roughly ±20 m are obtained.