Material coherence and life cycle of a wildfire-generated stratospheric vortex

Abstract

Pyro-cumulonimbus convection associated with extreme wildfires can generate long-lived vortical structures in the stratosphere. These structures have been described as coherent, yet a rigorous material characterization has remained lacking. Here we provide such a characterization by applying geodesic vortex detection to reanalysis winds during the 2019--2020 Australian bushfires. We identify a coherent Lagrangian vortex, dubbed \emph{Koobor}, whose boundary is given by materially coherent loops exhibiting nearly uniform stretching and strong resistance to filamentation over finite time intervals of up to 40~days. The detected vortex extends across multiple isentropic levels, revealing a vertically organized evolution with delayed onset and reduced persistence at higher levels. Taken together across isentropic levels, the reconstructed life cycle indicates that \emph{Koobor} maintained quasi-material coherence for nearly 60~days from its first detection, through a sequence of overlapping materially coherent boundaries rather than a single boundary advected over the entire period. Our results establish a material framework for wildfire-induced stratospheric vortices and provide a dynamically consistent description of their life cycle, from formation to decay.