Does ENSO set the footprint of extreme rainfall? Insights from dynamical eddy length scales

The spatial footprint of extreme rainfall events (EREs) governs the extent of affected regions and strongly influences flood severity and socio-economic impacts. While changes in the intensity of precipitation extremes are relatively well understood, a robust physical framework for characterising their spatial scales remains lacking. In particular, it is unclear to what extent large-scale dynamical constraints regulate the size of extreme precipitation systems if they. In this study, we investigate whether the theoretical eddy length scale, specifically the Rhines scale and the Rossby radius of deformation, can provide a physical basis for understanding the spatial extent of EREs during ENSO. We examine whether variations in these length scales are reflected in observed changes in ERE size during  El Niño–Southern Oscillation (ENSO), which is known to modulate the large-scale background flows. By stratifying EREs according to ENSO phase, we assess how changes in the background circulation during ENSO influence the relationship between eddy length scales and the spatial footprint of extreme rainfall. This work would provide a dynamical framework linking large-scale atmospheric eddy scales to precipitation extreme size. Results to be presented at the conference will discuss on the extent to which theoretical length scales constrain ERE spatial organisation and how these constraints vary across ENSO phases, with implications for understanding and projecting flood risk under climate variability.