A linear study of the effects of heating and orography on westerly airstreams with particular reference to monsoonal flow over northern Australia

A linear, steady-state model for the forcing of unsheared westerly air-flow by orography and surface heating has been produced. In a westerly air-flow, topography produces an upstream effect which extends further than in an easterly. Downstream, the topography forces a mixture of Rossby waves as well as shorter internal gravity waves modified by the Coriolis force. Long Rossby waves are not excited by easterly flow, so that upper air perturbations in a westerly have larger amplitudes than in easterly flow. A bounded, steady-state solution to the problem of westerly winds over a heated surface cannot be found. A bounded solution can be obtained if the appropriate amount of compensatory cooling is introduced on the eastern side of the heating. The heating results in negative perturbation pressures, and an overall equatorwards displacement of the flow, while the cooling produces positive perturbation pressures and a polewards displacement of the flow.