ON THE MECHANISM OF OVERREFLECTION OF A BAROTROPIC ROSSBY-WAVE

Using a simple model, Re reexamine the mechanism of overreflection (OR ) of a barotropic Rossby wave proposed by Lindzen and his colleagues. Though our model is somewhat artificial, it is advantageous to treat e ssential characters of a Rossby wave concerning the OR. It is clarifie d that the reversal of the relation between the direction of momentum flux and group velocity across an inflection point in the region where the WKB approximation is valid is essential for the occurrence of OR. As was demonstrated for the gravity wave case by Lindzen and Barker ( 1985), it is found that reflection layers behind the critical level is not important for the OR of a Rossby wave.