Analytic Model for Zonal Winds in the Tropics 501

We consider the zonal mean circulation on an equatorial &plane and obtain analytic solutions for small-amplitude disturbances in response to sources of heat and momentum. The effect of dissipation is roughly approximated by using assumed constant drag and radiative damping terms. We apply the model to the tropospheric zonal winds, temperatures, and meridional circulation to give simple insights into the maintenance of the observed mean state of these parameters by the existing sources of heat and momentum. The heat source consists of a relatively sharp maximum in heating at the Equator caused by latent heat release in the tropical rainbelt against a relatively smooth background of mean radiative cooling. As a momentum source, we use the convergence of horizontal eddy momentum fluxes. Numerical results are presented for an idealized annual mean circulation. The model solutions show how the thermal and momentum sources jointly maintain the zonal wind distribution. A concomitant meridional circulation redistributes the heat and momentum, allowing the temperatures to remain in balance with the zonal wind. This is part I of a two-part study.