Large scale perturbations in extratropical atmosphere—Part I: On rossby waves

This study reexamines the propagation mechanism and geostrophic property of the classical two dimensional Rossby waves in a non-divergent barotropic atmosphere. It will be found that propagation of large scale atmospheric waves depends crucially on horizontal divergence. A small Rossby number in Rossby waves is not sufficient for the waves to have a small ageostrophic component, because the two dimensional classical Rossby waves do not manifest the geostrophic balance as good as observed in the atmosphere.