Hadley Circulations in Radiative–Convective Equilibrium in an Axially Symmetric Atmosphere

Abstract

Hadley circulations in radiative?convective equilibrium are investigated using an idealistic axially symmetric model. Calculations show that the distribution of temperature in the Hadley cell is controlled by the moist process; the vertical profiles are close to the moist-adiabatic profile in the precipitating ascent branch, and the latitudinal distribution is nearly uniform. A sharp meridional temperature gradient exists within the poleward sloping boundary of the cell. Similar to Held and Hou, the latitudinal gradient of the vertically averaged temperature is determined by the cyclostrophic wind balance with the angular momentum?conserving flow in the upper layer. The region where the Hadley cell exists can easily be predicted from the relationship between the profiles of the surface temperature and the vertically averaged temperature. Under the condition that the solar flux is specified, however, because of the interaction between the atmospheric circulation and the surface temperature, the behavior of the Hadley cell is a little more complicated. In particular, if the rotation rate is faster than or equal to the terrestrial value, two peaks of the upward motion exist on both sides of the equator. Contrary to the traditional view of a steady indirect cell (the Ferrel cell), a systematic multicell structure exists in the middle and high latitudes. The horizontal scale of the cells is about 1000 km. They move equatorward at a speed of ?1 m s?1.