THE 2ND HAURWITZ MEMORIAL LECTURE - STATIONARY PLANETARY-WAVES

The linear theory for stationary Rossby waves excited by flow over lon g ridges is reviewed. The traditonal ''textbook'' model, in which ther e is no disturbance of the potential temperature surfaces or streamlin es upstream of the ridge, is shown to be inadequate. For both the beta -plane and the f-plane cases, pressure forces cause lifting of the ise ntropes and a cyclonic turning of the streamlines upstream of the ridg e. The beta-plane and f-plane solutions are, however, totally differen t for long ridges owing to the resonant excitation of stationary Rossb y waves and the vertical propagation of the long-wave components in th e beta-plane case. Curiously, the vertical displacement of the isentro pic surfaces is nearly identical in the beta-plane and f-plane solutio ns in the lower troposphere where the response is dominated by the sho rt-wave vertically decaying components.