Extratropical Transition of Tropical Cyclones in a Multiresolution Ensemble of Atmosphere-Only and Fully Coupled Global Climate Models

• DOI: 10.1175/jcli-d-21-0801.1
• Publication Date: 2022-05-11T14:19:33Z
• Authors: Alexander J. Baker; Malcolm J. Roberts; Pier Luigi Vidale; Kevin I. Hodges; Jon Seddon; Benoît Vannière; Rein J. Haarsma; Reinhard Schiemann; Dimitris Kapetanakis; Etienne Tourigny; Katja Lohmann; Christopher D. Ro...; Laurent Terray
• Keywords: Extratropical cyclone; African easterly jet; Tropical Atlantic; Forcing (mathematics); Oceanic basin; Atlantic hurricane; Cyclogenesis; Tropical cyclogenesis

Abstract Tropical cyclones undergo extratropical transition (ET) in every ocean basin. Projected changes ET frequency under climate change are uncertain and differ between basins, so multimodel studies required to establish confidence. We used a feature-tracking algorithm identify tropical performed cyclone phase-space analysis an ensemble of atmosphere-only fully coupled global model simulations, run at various resolutions historical (1950–2014) future (2015–50) forcing. Historical simulations were evaluated against five reanalyses for 1979–2018. Considering globally, ensemble-mean biases track genesis densities reduced the North Atlantic western Pacific when horizontal resolution is increased from ∼100 ∼25 km. At high resolution, multi-reanalysis-mean climatological frequencies across most basins as well basins’ seasonal cycles reproduced better than low-resolution models. Skill simulating interannual variability ∼0.3, which lower all cyclones. Models project increase decrease Pacific. explain these opposing responses by secular seasonality lower-tropospheric, pre-ET warm-core strength, both largely unique Atlantic. Multimodel consensus about clearer metrics intensity metrics. These results help clarify role quantify uncertainty surrounding warming climate.