A Study of Planetary Waves in the Southern Winter Troposphere and Stratosphere. Part I: Wave Structure and Vertical Propagation

Abstract

Planetary wave propagation in the southern winter troposphere and stratosphere is studied in an attempt to trace the origins of upward propagating disturbance. Daily geopotential girds from 1000 to 1 mb are analyzed for two 120-day winter seasons. A cross-correlation analysis technique is developed which allows coherent wave structure to be traced in time. Significant correlations are observed between the troposphere and stratosphere at finite time lags, indicative of vertically propagating waves. The observed vertical propagation time scales between the middle troposphere and middle stratosphere are on the order of 4 days for zonal wavenumber 1 (k=1), 1?2 days for k=2, and 1 day for k=3. The cross-correlation analysis also delineates the meridional and vertical structures of the transient (in time) planetary waves. Zonal wavenumber 1 fluctuations exhibit a vertical out-of-phase relationship between the midlatitude troposphere and atmosphere. Three out-of-phase maxima in latitude are observed in the troposphere, separated by 25?30° latitude, whereas a singe broad latitudinal maximum is found in the stratosphere. Wavenumbers 2 and 3 exhibit similar overall structures, quite distinct from that of k=1. Two out-of-phase maxima in latitude are observed in the troposphere, separated by 30?35° latitude, and the stratospheric variance is found to be coherent and in phase with that in the high latitude troposphere.