Westward traveling low-frequency hemispheric waves in the atmosphere

The resonant response of a "shallow water" atmosphere is examined by applying forcing for each hemisphere separately. It is shown, that westward traveling waves tend to concentrate in hemispheres of their forcing for real damping and this tendency is greater for low-frequency waves. These waves appear from the global Rossby modes and have resonant peaks only in one hemisphere. Since they are largely confined to one hemisphere and are thus qualitatively more similar to observations then are normal modes. The results were essentially unchanged when the basic experiments were repated many times, each with a different, randomly generated, forcing structure.