Frequency‐Dependent Behavior of Zonal Jet Variability

Recent work suggests that storm track diagnostics such as eddy heat fluxes and eddy kinetic energies have very small signatures in the first annular mode of zonal mean zonal wind, suggesting a lack of co‐variability between the locations of the extratropical jet and storm tracks. The frequency‐dependence of this apparent decoupling is explored in ERA‐Interim reanalysis data. The annular modes show similar spatial characteristics in the different frequency ranges considered. Cancellation between the signatures of storm track diagnostics in the leading low‐pass and high‐pass filtered annular modes is evident, partly explaining their small signature in the total. It is shown that at timescales greater than 30 days, the first zonal wind mode describes latitudinal shifts of both the midlatitude jet and its associated storm tracks, and it appears that the persistence of zonal wind anomalies is sustained primarily by a baroclinic feedback. Key Points Southern Hemisphere annular modes show similar spatial features under time filtering Cancellation of storm track signatures in first annular mode at low/high frequencies explains weak signal in total At periods greater than 30 days, the first annular mode explains shifts of both the jet and storm tracks