What determines the width of the tropical belt?

Abstract:

The history of theories for the width of the Hadely cell or the "tropical belt" is reviewed. The starting point will be a discussion of why it is meaningful to think of the zonally averaged ageostrophic flow, the Hadley cell, as the key to any theory of the width of the tropics. The linear (low Rossby number) perspective will be described next, followed by discussion of its limitations. Nonlinear theories based on angular momentum conservation and energy conservation, introduced to address these limitations, will then be outlined. It will then be shown that one has to compromise between these two limiting cases in order to address how latent heating affects the width of the tropical circulation, by coupling the strength of the Hadley cell to its width. El Nino will be used as an example of this coupling. If time permits, theories for the connections between ITCZ displacements and the width of the tropics will be introduced.