Middle and High Latitude Southern Hemispheric Oscillations on the 35—60 Day Time Scale

Abstract

Geopotential height fluctuations are examined in the extratropical Southern Hemisphere on the 35?60 day time scale. These fluctuations, in 200 mb geopotential height one-point correlation maps and anomaly maps, are shown to behave like quasi-stationary wavetrains with eastward energy propagation. The wavetrains follow an elliptically shaped circuit identifiable from low Southern latitudes in the Indian Ocean to the coast of Antarctica near 70°W. Weak correlations are found between the midlatitude wavetrain and 35?60 day brightness temperatures over the Indian Ocean. Nevertheless, a puzzling lack of correlation exists between the midlatitude 35?60 day signals and the anticipated subtropical wavetrain entry?exit region south of the tropical correlations. Eliassen?Palm flux calculations reveal strong momentum fluxes in the upper troposphere while the divergence is mostly negative throughout the troposphere. These observational results constitute several tests for models, viz., the existence and amplification of the midlatitude fluctuations and their quasi-stationary nature.