Interhemispheric Teleconnections from Tropical Heat Sources in Intermediate and Simple Models

Themechanismsthatcontroltheinterhemisphericteleconnectionsfromtropicalheatsourcesareinvestigated using an intermediate complexity model [a quasi-equilibrium tropical circulation model (QTCM)] and a simple linear two-level model with dry dynamics. Illustrating the interhemispheric teleconnection process with an Atlantic warm pool principal case, the heat source directly excites a baroclinic response that spreads across the equator. Then,threeprocesses involvingbaroclinic‐barotropicinteractions—shearadvection, surfacedrag, and vertical advection—forcea cross-equatorial barotropicRossbywaveresponse.Ananalysis ofthese processes in QTCM simulations indicates that 1) shear advection has a pattern that roughly coincides with the baroclinic signal in the tropics and subtropics, 2) surface drag has large amplitude and spatial extent and can be very effective in forcing barotropic motions around the globe,and 3)vertical advection has a significantcontribution locally and remotely where large vertical motions and vertical shear occur. The simple model is modified to perform experiments in which each of these three mechanisms may be included or omitted. By adding surface drag and vertical advection, and comparing each to shear advection, the effects of the three mechanisms on the generationandpropagationofthebarotropicRossbywavesareshowntobequalitativelysimilartotheresultsin QTCM. It is also found that the moist processes included in the QTCM can feed back on the teleconnection process and alter the teleconnection pattern by enlarging the prescribed tropical heating in both intensity and geographical extent and by inducing remote precipitation anomalies by interaction with the basic state.