A modeling study of the effect of the Andes on the summertime circulation of tropical South America

Abstract

A simple linear two level model of the atmosphere is developed. By blocking the lower layer of the model with a meridional wall, the interaction between diabatic forcing centered in the Amazon basin and the Andes is studied. This forcing can be considered a source of Rossby waves that scatter from the above partial barrier. The scattering process is examined analytically by making the long-wave approximation. Numerical solutions without the long-wave approximation are then considered and the effects of the above scattering process are examined. the upper level circulation is shown to be qualitatively similar to that obtained without a barrier. The low-level circulation west of the barrier is weak in the winds and consists of a positive geopotential response centered at approximately 30°S. To the east, the circulation near the barrier shows similarity to models of the Somali jet. The model produces quite strong trade winds and places a low-pressure center in approximately the position where one is actually observed. -from Author