Response of idealized Hadley circulations to seasonally varying heating

Abstract

[1] The response of Hadley circulations to displacements of the latitude of maximum heating is investigated in idealized axisymmetric and eddy-permitting models. Consistent with an earlier study and with theory for the nearly inviscid limit (Lindzen and Hou, 1988), the strength of the Hadley circulation is sensitive to displacements of heating: the winter cell strengthens and summer cell weakens when the maximum heating is displaced off the equator. However, in conflict with the nearly inviscid limit but consistent with observations of Earth's atmosphere, the strength of an annually averaged Hadley circulation is comparable to the Hadley circulation driven by an annually averaged heating. The disagreement between these results and the nearly inviscid limit is ascribed to vertical diffusion of momentum and dry static energy in the axisymmetric model and to baroclinic eddy fluxes in the eddy-permitting model. Nonlinear amplification of the annually averaged Hadley circulation is only seen near the upper boundary in simulations with a rigid lid near the tropopause, suggesting that the amplification is an artifact of the upper boundary condition.

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