Replicating the Hadley Cell and subtropical jet disconnect in idealized atmospheric models

Abstract. Recent work has shown that variability of the subtropical jet's (STJ) latitude, ΦSTJ is not coupled to that of the Hadley Cell (HC) edge, ΦHC, but the robustness of this disconnect has not been examined in detail. Here, we use meteorological reanalysis, comprehensive climate models, and an idealized atmospheric model to determine the necessary processes for a ΦHC and ΦSTJ disconnect. We find that a decoupling can occur in a dry general circulation model, indicating that large-scale dynamical processes are sufficient to reproduce the metrics' relationship. It is therefore not reliant on explicit variability in the zonal structure, convection, or radiation. Rather, the disconnect requires a sufficiently accurate climatological basic state. Further, we confirm that the robust disconnect between ΦSTJ and ΦHC across the model hierarchy reveals the features' differing sensitivities to midlatitude eddy momentum fluxes; ΦHC is consistently coupled to the latitude of maximum eddy momentum flux but the ΦSTJ is not.