THE EFFECT OF CONCENTRATED PV GRADIENTS ON STATIONARY WAVES

The author reexamines the Charney-Drazin problem with special attentio n to the concentration of potential vorticity gradient in the neighbor hood of the tropopause. It is found that the degree of concentration h as a profound effect on the response to stationary forcing, with great er concentration leading to greater response. Smoothing the concentrat ion either analytically or numerically (by using coarser resolution) b oth lead to reduced responses, especially at higher wavenumbers. The r esults suggest a potentially important interaction between baroclinica lly unstable eddies and stationary waves. Insofar as the former act to mix potential vorticity in the troposphere while concentrating gradie nts at tropopause levels, they significantly condition the basic state for the latter.