The Effect of Moisture on the Hadley Circulation: Simulations with an Idealized GCM

In simulations of global change, the tropical Hadley circulation expands as the temperature increases. We investigate dynamical mechanisms responsible for the response of the Hadley circulation to climate changes. In simulations with an idealized dry GCM, in a climate resembling that of present-day Earth, the strength and extent of an equinox Hadley cell are controlled by eddy fluxes and baroclinic instability in the subtropics, leading to an expansion of the Hadley cell with increasing tropical static stability (Walker & Schneider 2006). We investigate the extent to which these results carry over to moist atmospheres with simulations with an idealized moist GCM coupled to an oceanic mixed layer. We vary the optical thickness of a longwave absorber and study the response of the Hadley circulation.