A Primitive Equations Model Study of the Effect of Topography on the Summer Circulation over Tropical South America

Abstract

A nonlinear, primitive equations model with five levels in a σ coordinate is applied to study the effects of idealized topography on the summer circulation pattern over tropical South America. The model circulation is forced by prescribed latent heating centered over the Amazon Basin. Both the steady and the transient components of the response are considered and compared with the corresponding components in the absence of topography. It is found that topography blocks low-level inflow from the equatorial Pacific and leads to the development of a steady, northerly jet that is fed from the tropical Atlantic. Other important effects of topography on the response to steady heating are found in the low-level field of vertical motion. The effects of topography on the response to transient heating are described in terms of a component reflected to the east and a component transmitted to the west by the topography.