Quasi-resonant Rossby waves and the dynamics of extremes: an idealized modeling perspective

Abstract:

Quasi-resonant Rossby waves were proposed by Petoukhov et al. (2013, PNAS) as a mechanism underlying certain extreme weather events, including both heat waves and heavy rainfall. Many subsequent studies have made use of this idea, primarily to interpret reanalysis data or full-physics general circulation model simulations.

In physical terms, the quasi-resonance theory is an application of the linear barotropic vorticity equation (with forcing and dissipation) to the analysis of observed zonal mean jets. Needless to say, the implicit assumption that this is an appropriate framework for analyzing extreme events in a nonlinear three-dimensional atmosphere is a strong one. In our view, this assumption (and its many sub-components) could and should be better tested.

We plan to conduct such tests using an idealized general circulation model. By iteratively constructing the thermal and/or momentum forcing fields for the model, we expect to achieve control of its zonal mean flow and thus the basic state experienced by barotropic Rossby waves. We will then investigate the properties of quasi-stationary Rossby waves in such simulations to see whether they agree with the predictions of the quasi-resonance theory. Implications of our results for studies of the observed past and projected future climate will be discussed.