The Effect of Compressibility on Barotropic and Baroclinic Instability

The effect of compressibility on two-dimensional barotropic and baroclinic growth rates is examined by means of a linearized nonhydrostatic compressible model. It is shown that the growth rates are diminished when compressibility is included because perturbation internal energy resents a sink of basic-state kinetic energy when work is done to compress the medium. Nonlinear simulations provided by compressible and incompressible versions of the ZETA model show that the solutions are nearly identical, but the compressible solution develops more slowly than the incompressible one, consistent with the linear analysis.