Tropospheric Rossby wave breaking and variability of the latitude of the eddy-driven jet

A dry general circulation model is used to investigate the connections between Rossby wave breaking and the latitude of the midlatitude tropospheric eddy-driven jet. An ensemble of experiments is constructed in which the jet latitude is influenced by a midlatitude tropospheric temperature anomaly that resembles observed climate change and by the imposition of a stratospheric polar vortex, and the distribution of Rossby wave breaking frequency is examined for each experiment. The shift in wave breaking per degree latitude of jet shift is then compared for three different sources of jet movement: the tropospheric baroclinic forcing imposed in midlatitudes, the imposition of a stratospheric polar vortex, and the internal variability of the midlatitude eddy-driven jet. It is demonstrated that all three sources of jet movement produce a similar change in Rossby wave breaking frequency per degree of jet shift. Hence, it is difficult (if not impossible) to isolate the ultimate cause behind the shift in Rossby wave breaking in response to the two external forcings.