Hurricane size is strongly limited by the Rhines scale: experiments with a barotropic model

Abstract:

Recent work found evidence using aquaplanet experiments that the hurricane size is limited by the Rhines scale on Earth. Theoretically, the Rhines scale is hypothesized to limit storm size via the radiation of Rossby waves for circulations significantly larger than this scale. Although this conceptual hypothesis is well defined, the actual dynamical details remain unclear. This study aims to examine how the Rhines scale limits hurricane size. To approach this, we perform dynamical experiments using a simple barotropic model on beta-plane with a hurricane-like vortex defined by the theoretical model of Chavas et al. (2015) for the axisymmetric near-surface tropical cyclone wind field. This study conducts several sets of experiments systematically varying key parameters, including beta and initial vortex size to investigate the detailed interaction between the vortex and Rossby waves. Across experiments, storms whose outer size is larger than its corresponding vortex Rhines scale shrink back towards this scale at a rate proportional to the ratio of the two scales. This response is relatively fast (on the order of few days) and hence would be reasonably expected to limit storm size in nature, too. These numerical experiments give us clearer insight into the dynamics of wave-vortex transition, which will help improve understanding of how the Rhines scale limits the size of hurricanes on Earth.