The evolution of cyclonic and anticyclonic Rossby wave breaking morphologies and their importance in extremes

Rossby waves are fundamental meteorological phenomena in the extratropics. When these waves amplify and break, they often lead to extreme weather events, including heatwaves, heavy rainfall, and strong winds. Here we apply an objective classification method to identify equatorward anticyclonic and cyclonic Rossby wave breaking morphologies, analogous to the LC1 and LC2 types identified in previous research. Anticyclonic Rossby wave breaking zones are shown to evolve as expected, representing the barotropic decay of baroclinic Rossby wave packet. Composite analysis of the evolution of cyclonic Rossby wave breaking morphologies however shows that these morphologies develop from the debris of preceding anticyclonic Rossby wave breaking. Cyclonic morphologies are further linked to Rossby wave packet generation and downstream development. The role of Rossby wave breaking in extreme weather is illustrated through the example of heavy rainfall along Australia’s east coast, emphasizing its importance in the generation of such extremes.