On the instability of a three-layer atmosphere with an isentropic stratosphere

The linearized stability problem for a three-layer model, with an isentropic stratosphere as the uppermost layer, is studied. The model consists of soft tropopause and mid-tropospheric front. By making the tropopause rigid or by shrinking the depth of the stratosphere to zero one obtains the symmetric two-layer model. By eliminating the tropopause one obtains an asymmetric two-layer model. Both cases β = 0 and β ≠ 0 are considered for three-layer model. The structure of a growing wave and its physical interpretation are given for a three-layer model β = 0 case.