A ubiquitous wavenumber-5 anomaly in the Southern Hemisphere during FGGE.

Abstract

Predominant wavenumber-5 patterns frequent the temperature fields of the lower stratosphere of the Southern Hemisphere during the summer months of FGGE. These pentagonal features, of broad latitudinal extent, appear to remain quasi-stationary or propagate eastward with periods in the order of 10 days. Ensemble statistics over the summer season confirm the presence of large-amplitude wavenumber-5 anomalies in the geopotential fields. Magnified height amplitudes appear in the zonal spectra at wave 5, near the tropospheric jet core: 50oS and 300 mb. The enhanced temperature anomalies in the lower stratosphere arise not only from the magnified geopotential amplitude of wavenumber 5, but also from its sharp evanescence above the jet. Time series analysis reveals that the peak in rms amplitude results primarily from the fluctuating contribution.-from Author