Using a linearized model with constant mean wind on an equatorial β-plane, two types of atmospheric response to steady tropical forcing are studied by an eigenmode analysis. The first type is the less rotationally trapped “barotropic” motions which show some of the characteristics of the teleconnection patterns observed by Bjerknes (1966) and Horel and Wallace (1981). The second type is the more rotationally trapped, warm-core, deep baroclinic motions which resemble the Walker circulations. The analysis reveals several important inadequacies in previous modeling studies and provides a relatively comprehensive explanation of the dynamics of both types of motions. A vertical normal mode consideration shows that the barotropic-type motions are difficult to excite by internal beating. Surface heating, which has been neglected in many previous numerical modeling studies, is found to be important in directly forcing this type of motion. Furthermore, the possible contribution by large equivalent depth internal modes to the teleconnection response was not considered in these studies. A ray tracing approach is used to demonstrate the importance of the rotational trapping effect on the propagation of these deep internal modes. A horizontal normal mode analysis shows that the most prominent responses in all cases are band disturbances of Kelvin and Rossby modes. In addition, in a westerly mean wind with a speed within the range of the Rossby wave phase speed, Rossby mode lee waves are also excited. These lee waves are replaced by Rossby mode evanescent disturbances in other mean winds. For large equivalent depths in westerlies, the band disturbances combine to produce the teleconnection pattern. For all equivalent depths, the Rossby mode is very important in the equatorial zonal wind band response on both the cast and the west sides of the forcing. For small equivalent depths this makes the Rossby mode an important component of both the eastern and the western Walker circulations. Several previous models obtained only the Rossby and Kelvin band solutions due to their use of a long- wave approximation. This approximation distorts the responses, with the most serious distortions occurring in mean westerlies. Although the tropical mean wind is often easterly, it is argued that the westerly mean wind solution is probably more relevant to the Walker circulations due to their observed transient nature and the dynamics of transient forcing. In the westerly mean wind solution the Rossby lee waves east of the forcing substantially reduce the longitudinal extent of the zonal wind band to a value comparable to that observed.
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