A Comparison of the Dynamic Life Cycles of Tropospheric Medium-Scale Waves and Stratospheric Planetary Waves

Abstract

This paper presents a comparison of the dynamic life cycles exhibited by a) baroclinically-forced medium-scale waves in the Southern Hemisphere (SH) troposphere, and b) tropospherically-forced, vertically-propagating planetary waves in the SH winter stratosphere. Cross correlation analyses of nine years of daily data reveal the characteristic EP flux signatures and wave-induced mean flow tendencies during wave growth, maturity and decay. Wave source and sink regions are shown, and strong midlatitude Rossby wave radiation towards low latitudes is observed in both instances. Tropospheric waves are shown to influence the zonal mean flow deep into the lower stratosphere (up to 30 mb). Wave-induced mean flow accelerations in the troposphere are to a large degree reversible between wave growth and decay, whereas the stratospheric waves exert a predominant oneway influence only (zonal flow deceleration). The midlatitude stratospheric waves are also shown to have a delayed, secondary influence in the subtropical upper stratosphere; this may be the statistical signature of planetary wave reflection (or overreflection) from a low latitude critical region.