Global eddy-induced variation in the intensities of tropical cyclones

Abstract The life cycle of tropical cyclones (TCs) is characterized by phases of intensification and weakening, which depend on changes in TC intensity. Eddies, ubiquitously distributed across the global ocean, frequently interact with TCs and significantly impact their intensity. This study demonstrates that changes in TC intensity, quantified by wind speed, are primarily determined by the polarities of eddies and the relative positions of TCs to these eddies. Eddies induce dynamic changes in sea surface temperature anomalies (SSTAs) in the central region via mixing and vertical transport, while disturbing the SSTA along the periphery through horizontal advection. As these processes occur simultaneously, central anticyclonic (cyclonic) eddies are associated with positive (negative) SSTAs, whereas on the eastern equatorward (eastern polarward) periphery, they are linked to negative (positive) SSTAs, influencing TC intensity. Consequently, anticyclonic (cyclonic) eddies promote (inhibit) the intensification and inhibit (promote) the weakening of TCs, with more significant effects when locating on the equatorial (polar) side of TCs. Specifically, positive (negative) SSTAs in the central regions of anticyclonic (cyclonic) eddies provide more (less) heat to TCs, thus promoting (inhibiting) their development. Additionally, when anticyclonic (cyclonic) eddies are located on the equatorial (polar) side of TCs, the advection induced positive (negative) SSTA along the periphery is closer to the TCs, thereby more effectively promoting (inhibiting) TC intensification. Overall, these findings offer valuable insights into the influence of oceanic dynamics on the modulation of TC intensity.