On stochastic perturbation of simple blocking models

Abstract

Abstract In this paper we discuss some problems connected with the stochastic dynamics generated by the effect of small random perturbations acting on prototype equations governing large‐scale flows. We focus on the features of the process which occur when the main instability is the result of orographic forcing on simple barotropic motion. In particular, we study a three‐mode truncation of barotropic flow over topography when a stochastic white forcing acts on the system. We found analytical estimates of the exit times from the attraction domains of the steady solutions of the model. The exit times were found to range widely as a function of the zonal forcing. In addition, we included a representation of the large‐scale forcing in terms of a red process. We found that as a function of the variance of the perturbing process and the model's parameters, the bimodal nature of the barotropic model can be obscured.