Spiral Patterns of the Rossby Wave

Abstract

AbstractWe use quasi‐geostrophic motion equations describing large‐scale motion in the atmosphere to obtain the steady three‐dimensional stream field and the corresponding potential temperature, vorticity and divergence fields. Among them the three‐dimensional velocity field constructs a nonlinear autonomous dynamical system in the physical space. It is shown that the Rossby wave has a tilting spiral structure, which represents that the stream field is horizontal convergence at lower level and ascending motion in front of trough, but descending motion and horizontal divergence at lower level behind the trough. And these make westerlies momentum from the north and the south concentrate on the center regions of the Rossby wave. This is known ordinarily as the ‘negative viscosity’ phenomena. It implies that the rotation of the earth and mean current are playing an important role in forming the spiral structure of the Rossby wave.