The effect of concentrated PV gradients on stationary waves

The author reexamines the Charney-Drazin problem with special attention to the concentration of potential vorticity gradient in the neighborhood of the tropopause. It is found that the degree of concentration has a profound effect on the response to stationary forcing, with greater concentration leading to greater response. Smoothing the concentration either analytically or numerically (by using coarser resolution) both lead to reduced responses, especially at higher wavenumbers. The results suggest a potentially important interaction between baroclinically unstable eddies and stationary waves. Insofar as the former act to mix potential vorticity in the troposphere while concentrating gradients at tropopause levels, they significantly condition the basic state for the latter.