ERTEL POTENTIAL VORTICITY AND NONLIN-EAR SYMMETRIC INSTABILITY PROBLEM IN THE ATMOSPHERE

In this paper, the Lagrang parcel theory was applied to simplify the symmetric motion equation in the atmosphere, on the base, bifurcation and catastrophe theories were used to discuss the role of Ertel potential vorticity in the symmetric instability under the condition of the environmental geostrophic wind with nonlinear shear distribution, and some new results were obtained.