Seasonality of the Eddy Driven Jet Response to Constant Forcing

An important feature of the large-scale atmospheric circulation's response to climate change is the movement of the eddy-driven jets. Both the annual mean response and the seasonal response of the jet to climate change have been previously studied; however, the seasonality of the jet response has not been attributed to the seasonality in the forcing or the seasonality in the atmospheric dynamics. Here, a set of idealized modeling experiments is used to explore the seasonality of the dynamics while holding the forcing constant. The GFDL dry dynamical core is perturbed with different thermal forcings intended to simulate climate change--an upper tropical tropospheric heating (approximating greenhouse gas warming) and a polar surface warming (simulating Arctic amplification)--while a seasonal cycle is simulated by adjusting the equilibrium temperature gradient. The simulations indicate that eddy-driven jet response has a distinct seasonality, with a greater shift in jet position occurring in the summer months compared to the winter months. This enhanced summer response is robust to changes in the strength and the vertical position of the heating source. Possible dynamical mechanisms that may explain the seasonality of the eddy-driven jet response are also explored.