Influence of Meridional Constraints on Low-Frequency Variability and its Response to Climate Change

February 23, 2012

Elizabeth Barnes

Hosted by David Thompson

Abstract

The eddy-driven jet is located in the midlatitudes, bounded on one side by the pole and often bounded on the opposite side by a strong Hadley-driven jet. This work explores how the eddy- driven jet and its variability persist within these limits. It is demonstrated that as the jet is located at higher latitudes, the leading mode of variability of the jet changes from a meridional shift to a pulse, while the persistence decreases. Looking equatorward, a similar change in eddy-driven jet variability is observed when the jet moves equatorward toward strong subtropical winds. In both the poleward and equatorward limits, the change in variability from a shift to a pulse is due to the modulation of eddy propagation and momentum flux. With human-induced climate change, these results predict a reduction in eddy-mean flow feedback strength, which implies a reduction in the time scale of the leading mode of variability in the troposphere. This work highlights how important it is for models to correctly position the jet, as slight deviations in latitude can cause large changes in the leading mode of variability and thus could influence the circulation's response to external forcings.