On the structure of transient atmospheric waves. Part I



The structure of baroclinic waves on a zonal current is investigated. Using a two level, quasi-nondivergent model it is possible to derive two nonlinear equations describing the changes in time of the ratio of the amplitudes and the phase angle difference between the vertically averaged wave and the thermal wave. All steady states and their linear stability properties are found. It turns out that one stable steady state describes a westward sloping wave increasing in amplitude with height This state corresponds to the asymptotic state of the amplifying baroclinc wave. Another steady state with the opposite slope is unstable Four additional steady states are found for sufficiently small windshears. They are stable, but of an oscillatory nature and are either vertical or sloping half a wave length.


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