Eddy influences on the Hadley circulation

The physical mechanisms driving these responses remain unclear, in part because of the interactive nature of eddy-mean flow adjustment. Here, a modeling framework is developed which separates the mean flow and time-mean eddy flow in a gray radiation general circulation model with simple representations of ocean heat transport and ozone.

In the absence of eddies, with moist convection and weak numerical damping, the Hadley cell is confined to the upper troposphere and has a vanishingly small poleward momentum flux. Eddies allow the cell to extend down to the surface, double its heat transport, and flux momentum poleward, the latter two being basic consequences of a deepening of the circulation. Because of convection and damping—which mimics, in part, the effect of eddy stresses—previous work may have underestimated the impact of eddies on earth's circulation.