On air mass motion along a high slightly curved mountain ridge

A steady-state, space, large-scale, non-linear problem of the air mass motion along a ridge is considered in the framework of bulk theory. As compared with published papers, in which similar problems were solved in the framework of shallow water theory, in the presented paper the problem is generalized to take into account, in the first approximation, the interaction between thermal field of the air mass and its dynamics and the effect of stably stratified overlying atmosphere. For the first time the case of Southern hemisphere is discussed. The main goal of our paper is determining qualitative regularities of the process under investigation on the basis of analytical solution of the problem. Therefore an extremely simplified problem is considered, namely, the mountain ridge is replaced by the infinitely high vertical wall, whose bends coincide with the ridge bends, while the remaining terrain is replaced by the horizontal plane. The influence of turbulence is also ignored. As the result, the system of determining equations can be integrated and, after the boundary layer type simplification, the problem is reduced to the solution of the two-parameter algebraic transcendental equation jointly with the set of relatively simple relations for the fields of meteorological elements. One may solve this equation mentally by the graphic method with allowance for these auxiliary relations and ridge configuration, to determine the character of the air mass motion and find the main qualitative regularities of the meteorological fields. In various flow types the following features may appear: a zone of strong winds and even storms; a zone of closed circulation; an orographic stationary front and the downward warm air intrusion area located between this front and the ridge. On the basis of numerical solution of the above-mentioned algebraic equation, specific flow patterns are calculated. It is shown that in some cases the solution of the generalized problem differs qualitatively from the solution obtained on the basis of the shallow water theory.