Resonant Rossby wave mechanism for extreme weather performs poorly in simple model test.

Abstract

Quasiresonant amplification (QRA) of quasistationary Rossby waves is a mechanism for mid-latitude extreme weather that has been repeatedly proposed but subjected to only limited testing. Here, we test QRA theory by attempting to create quasiresonant Rossby waves in an idealized general circulation model, in which we identify mean flow states expected to be suitable (and unsuitable) for the existence of quasiresonant Rossby waves and quantify the associated wave amplitudes. For mean flow conditions thought to be suitable for QRA, waves of the relevant wave number are instead found to be weaker than under conditions ostensibly unsuitable for QRA. This situation cannot robustly be changed by altering the definition of a QRA-suitable mean flow. These findings cast doubt on the value of QRA theory in its current form as an interpretive tool and more generally warrant caution in the use of purely two-dimensional theories and/or zonally averaged flows to explain tropospheric extreme event dynamics.