The temperature structure of the Southern Hemisphere stratosphere August – October 1971

Abstract

AbstractThe temperature field in the Southern Hemisphere stratosphere from 100 to 1mb during August to October 1971 is described using observations from the Selective Chopper Radiometer on the Nimbus IV spacecraft.Zonal and monthly mean wind fields for September and October 1971 deduced from these temperatures are presented and the behaviour of the zonal temperature waves with wavenumbers 1, 2 and 3 is discussed. The largest amplitudes of wavenumbers 1 and 2 in the horizontal coincide broadly with the maximum westerlies. The amplitudes of wavenumber 2 are generally smaller at around 20mb than above or below. The amplitudes of both waves are small north of 30°S.Wavenumber 1 exhibits little vertical coherence throughout August and September. In October, however, the slope of the wave with height is much less variable, in spite of a slow eastward movement in early October and a westward movement in late October.Wavenumber 2 travelled eastwards with a fairly uniform rate of approximately 15·5° longitude per day between 15 August and 7 October but less uniformly at other times. Changes in wave amplitude at strato‐pause levels are associated with comparable changes near the tropopause. A maximum of wavenumber 2 amplitude on 26 September 1971 is associated with falling ZPE in the lower stratosphere and rising ZPE in the higher stratosphere. The dominant contribution to the eddy available potential energy is in the lower stratosphere.In the low stratosphere there is an inverse relationship in zonal and eddy available potential energies, rises in one form being associated with falls in the other. This inverse relationship is not well marked in the high stratosphere.