A Simple Atmospheric Model of the Local and Teleconnection Responses to Tropical Heating Anomalies

Abstract

A minimal complexity model of both the local and remote stationary responses of the atmosphere to tropical heating anomalies is described and demonstrated. Two levels are recast as baroclinic and barotropic components with thermal advection in the tropics neglected. The model is linearized about some idealized and realistic background wind fields and forced with a localized heating for illustration. In the tropics, the baroclinic responses are familiar from the Matsuno?Gill model; these excite barotropic responses by advective interactions with vertical background wind shear. The barotropic signals are in turn transmitted to high latitudes only in the presence of barotropic background westerly winds. For an El Niño?like equatorial heating, the barotropic response has anticyclones to the north and south of the heating reinforcing (opposing) the anticyclonic (cyclonic) baroclinic gyres in the upper (lower) troposphere. With realistic background flows, the model reproduces the hemispheric asymmetry of ENSO teleconnections. Further experiments show that the winter hemisphere is favored mainly because the summer hemispheric subtropical jet is farther from the heating latitude, suggesting that the summer hemisphere can still host robust stationary Rossby waves if the heating occurs in the vicinity of the jet. As an example, it is shown that summer heating over the Atlantic warm pool (AWP) can have a remote influence on the summer climate of North America and Europe.