A new split jet index is defined in this study, and the composites based on this index show that the cold-warm-cold tripole temperature anomaly starting from the South pole occurs in the South Pacific in association with the split-flow regimes and the non-split flow exists when the phase of the tripole temperature anomaly is reverse. The heat budget reveals that the temperature anomaly associated with the split/non-split jet is the response to the large-scale wave, not the forcing from the local diabatic heating. The localized E-P flux diagnostics and the stationary wave model diagnostics both illustrate that the split/non-split jet is maintained by the vorticity flux, and the vorticity flux is dominant over the heat flux, which has the opposite effect to the maintenance of the split/non-split jet.
The organization of high-frequency eddies by the low-frequency split/non-split jet has been studied. Two sets of linear runs of a simple GCM with random initial conditions for the split and non-split jet basic state respectively, have been conducted to establish the statistics of the storm tracks. The storm track anomalies that are caused by the split/non-split jet match the storm track anomalies that are associated with the split/non-split jet observed in the ECMWF reanalysis data, thus demonstrating that the low-frequency split/non-split jet does organize the high-frequency eddies. Our results suggest that there is a two-way feedback between the eddies and the mean flow in the low frequency variability of the SH winter split jet.
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