The latent heating feedback on the midlatitude circulation in a warming world

Midlatitude storms transport warm and moist air poleward and upward, releasing latent heat. Latent heating is thus organized by the
circulation but then modifies temperature gradients and winds, constituting a nonlinear feedback. We define the latent heating feedback
as the effects that arise from latent heating being coupled with the circulation. Because of its nonlinearity, the climatic effects of this
feedback are difficult to isolate and remain poorly understood.

By decoupling latent heating from the circulation in an atmospheric general circulation model, we show that the latent heating feedback
enhances storm track eddy diffusivity, modifying eddy heat fluxes beyond changes in mean baroclinicity. Simultaneously, tracked storms
occur at lower latitudes, intensify more, and propagate further poleward, while the subtropical jet strengthens as coupled latent heating
preserves lower latitude baroclinicity. The feedback response supports the idea that diabatic effects cause the “too zonal, too
equatorward” storm track biases in climate models.

Finally, we extend the analysis to climate change experiments where we isolate the contribution from the latent heating feedback on
storm intensity and eddy kinetic energy as the world warms. The feedback is most important in summer where it accounts for most of the
changes in eddy kinetic energy. In winter, the feedback is constrained. Isolating the latent heating
feedback helps to quantify how storminess changes as the atmosphere warms, which climate models currently struggle with.