Some Interhemispheric Comparisons of Medium-Scale Waves in the Lower Stratosphere

Abstract

Remarkable domination of the summer Southern Hemisphere circulation by medium-scale features (zonal waves 4?7) has been reported. More recently, it has been shown that these features derive their energy from baroclinic instabilities of the mean state. As one aspect of attempting to further explain the unusual spectral peak and phase-time continuity of the SH waves, we use the same microwave satellite instrument to compare characteristics of medium-wale lower stratospheric temperature waves in the Northern and Southern Hemisphere (NH and SH, respectively) summertimes. Data from the Tiros-N Microwave Sounding Unit from August 1979 are analyzed here and compared with previous analyses for January 1979 reported by Yu and others. The interhemispheric comparison reveals that summertime medium-scale waves in the NH do not exhibit the striking phase-time continuity of their SH summer counterparts. In addition, winter NH medium-scale waves are also found to have less phase-time continuity than those in the SH winter. The mason for the interhemispheric difference in maintenance of the medium-scale waves, especially in summertime, remains to be explained.