Quasiresonant Rossby Wave Amplification Theory Fails a General Circulation Model Test

The past decade has seen much discussion of quasiresonant amplification (QRA) of quasistationary Rossby waves as a possible mechanism for heat waves and other midlatitude extreme events. Much of the literature on QRA applies the underlying theory to the analysis of atmospheric data or model output, implicitly or explicitly assuming the theory’s validity. Here we conduct a clear test of the theory using an idealized general circulation model (GCM). By applying QRA theory to the zonal wind fields of our GCM experiments, we identify mean flow states expected to be suitable (and unsuitable) for the existence of quasiresonant Rossby waves. For mean flow conditions thought to be suitable for QRA, quasistationary waves of the ostensibly resonant zonal wavenumber are instead found to be weaker than under mean flow conditions thought unsuitable for QRA. Nor are the mean flow conditions supposedly favorable for QRA robustly conducive to the development of surface temperature extremes. In other words, QRA theory is not informative about surface temperature extremes and its core qualitative prediction about quasistationary wave amplitudes is incorrect. We therefore conclude that QRA theory provides little real insight into the causes of observed extreme weather events and is not likely to form a useful basis for projecting their future changes.