Consideration for the Tropopause's Displacements in the Problem of Flow over Mountains

摘要

Within the framework of a two-dimensional,inviscid,stationary model,the problem of an unbounded(in height)two-layer quasi-static airflow over mesoscale mountains is considered.The airflow is characterized by a constant velocity and a discontinuity of temperature stratification at the inner interface(tropopause).The conjugation conditions for the flow fields at the boundary between the layers are formulated exactly,without the standard assumption of small perturbations.According to calculations,partial reflection of wave energy from the tropopause is substantially controlled by nonlinear effects associated with a finite height and shape of terrain.The tropopause's displacement from the initial(equilibrium)level has a stabilizing effect on the flow,thus interfering with the development of anomalously strong disturbances.As a result,the flow field remains statically stable within a considerably wider range of flow parameters and for a larger mountain heights than predicted in the context of the conventional linear theory.The results obtained in this study are indicative of the importance of a correct consideration of the dynamic interaction between the troposphere and the over lying layers during both simulation of the process of flow and analysis of real atmospheric situations over mountains.