A study on the excitation, establishment and transition of multiple equilibrium states produced by nearly resonant thermal forcing — part II: Theoretical analysis of the mechanism of multiple equilibrium states

Abstract

Based on the results acquired in Part I of this paper, analysis is made of the theoretical mechanism of thermal forcing multiple equilibrium states (MES) and their stability. The results are as follows: 1) nonlinear effect and external forcing are determinative factors for MES formation; 2) under proper “environmental conditions” the forcing can excite stable MES, particularly three types of solutions, two of which, with larger amplitude of resonance, are not sensitive to the change in the forcing intensity; while the other, i. e. the one of small amplitude, dependent significantly on it; 3) in general, the domain of parameter values for the MES existence increases, but the stability decreases, with increasing thermal forcing; 4) steady thermal forced waves are always unstable for the most part; 5) thermal driving and orographic effect act equally as dynamical triggers; 6) friction has significant influence upon the behavior of MES solutions. Analysis shows that the changes in the “environmental parameters”, such as the alteration of the shear of a basic current and intensity of the forcing, induce the transition between different equilibria.