The relations between jet stream, Hadely circulation, and eddy life cycle transitons in an idealized model of the global circulation

In its idealized form, the global circulation is a complex interaction between three components - the Hadley cell, midlatitude jet streams, and storms. This three-way interaction gives rise to multiple dynamical regimes, both for the Hadley circulation and the midlatitude jet streams. Model and observational studies have shown several kinds of dynamical regimes and transitions, related to each of these components, and to different flow characteristics. For example, there are thermally or eddy driven jets, a single or double jet, subtropical or polar jets, an angular-momentum-conserving vs eddy driven Hadley cell, and cyclonic and anti-cyclonic eddy life cycles. With the aim of bridging the gap between idealized models of one or two of these components, and idealized GCM studies, we modify a 2-level spherical quasi-geostrophic model to include the Hadley circulation by adding the agestrophic advection terms in the zonal mean component. This yields maybe the simplest model which explicitly resolves the main dynamical features of the Hadley circulation and midlatitude wave-mean flow interactions. We use this model to systematically examine the dominant balances behind these different dynamical regimes, and how the dynamical transitions associated with each of the three components relate to each other, and show how they relate to observed features of the circulation.