Report

Periodic Variability in the Large-Scale Southern Hemisphere Atmospheric Circulation

See allHide authors and affiliations

Science  07 Feb 2014:
Vol. 343, Issue 6171, pp. 641-645
DOI: 10.1126/science.1247660

You are currently viewing the abstract.

View Full Text

Log in to view the full text

Log in through your institution

Log in through your institution

Predictable Behavior

Few internally forced large-scale atmospheric circulation patterns exhibit periodic behavior, and those that do are centered in the tropics. Identifying these periodic processes is important for understanding the dynamics of weather. Thompson and Barnes (p. 641) report the discovery of a 20- to 30-day periodicity in the atmospheric circulation in the Southern Hemisphere. The oscillation could potentially drive large-scale climate variability throughout much of the mid-latitude Southern Hemisphere.

Abstract

Periodic behavior in the climate system has important implications not only for weather prediction but also for understanding and interpreting the physical processes that drive climate variability. Here we demonstrate that the large-scale Southern Hemisphere atmospheric circulation exhibits marked periodicity on time scales of approximately 20 to 30 days. The periodicity is tied to the Southern Hemisphere baroclinic annular mode and emerges in hemispheric-scale averages of the eddy fluxes of heat, the eddy kinetic energy, and precipitation. Observational and theoretical analyses suggest that the oscillation results from feedbacks between the extratropical baroclinicity, the wave fluxes of heat, and radiative damping. The oscillation plays a potentially profound role in driving large-scale climate variability throughout much of the mid-latitude Southern Hemisphere.

View Full Text