Non-Exponential Amplification of Disturbances in Uniform Basic Straining Flows

[摘要] Amplification of disturbances superimposed on a uniform basic straining flow is analytically investigated in a linearized barotropic dissipative system on an f-plane. The dissipation is assumed to be of a diffusive type. The temporal evolution of disturbance energy, which initially is imparted isotropically at every wave number, is examined. The results obtained are the following. (1) For a pure rotation, the straining flow does not affect the disturbance energy. (2) In the near future, the disturbance energy is amplified by the deformation, and the rotation does not partake it. (3) In the distant future, amplification of the disturbance energy by the straining flow also occurs, which depends on the rotation as well as the deformation. The behaviour crucially depends on which component, deformation or rotation, dominates.

[学科分类] 大气科学