The Role of Diabatic Heating in Ferrel Cell Dynamics

The Ferrel cell consists of the zonal mean vertical and meridional winds in the midlatitudes. The continuity of the Ferrel circulation and the zonal mean momentum and heat budgets imply a collocation of the eddy-driven jet and poleward eddy heat flux maxima, under certain assumptions, including the negligibility of diabatic heating. The latter assumption is questioned, since midlatitude storms are associated with latent heating in the midtroposphere. In this study, the heat budget of the Ferrel cell in both hemispheres is examined, using the JRA55 reanalysis data set. The diabatic heating rate is significant close to the center of the Ferrel cell during winter and at the ascending branch during summer in both hemispheres. The interannual variability shows a positive correlation between the diabatic heating rate in the midlatitude midtroposphere and the latitudinal separation between the eddy heat flux and the eddy-driven jet maxima during winter in both hemispheres. Plain Language Summary The midlatitude climate is affected by storms, organized in regions called "storm tracks." Storms are carried eastward by the midlatitude jet stream. The storm track and the jet stream are dynamically coupled, through the heat and momentum budgets. Here we use the heat and momentum budgets, and the continuity of the midlatitude meridional circulation cell, called the "Ferrel cell," to examine the connection between the latitudinal locations of the storm track and jet stream. We focus on the role of diabatic heating by latent heat release in midlatitude storms in the heat budget, and its effect on the circulation. Our analysis shows that the latitudinal separation between the storm track and jet stream increases as the diabatic heating in the midlatitude midtroposphere increases during winter. These results highlight the role of diabatic heating in the midlatitude circulation, which is often overlooked. Key Points Diabatic heating plays a key role in the midlatitude heat budget controlling the Ferrel cell Diabatic heating is concentrated at the Ferrel cell ascending branch during summer and around the Ferrel cell center during winter The diabatic heating rate is positively correlated with the wintertime separation between the eddy heat flux and the eddy-driven jet