Idealized Tropical Cyclones in Atmospheric General Circulation Models: The Impact of the Dynamical Core

Using General Circulation Models (GCMs) for tropical cyclone studies is difficult due to the relatively small size of the storms, the intense convection and multitudes of large-scale small-scale interactions. They are mostly unresolved at typical GCM resolutions of about 50-100 km, and still challenged at high resolutions between 15-30 km. Nevertheless, high-resolution GCMs are becoming a tool of choice to address tropical cyclogenesis for current and future climate conditions. Therefore, the physics and dynamics components of a GCM need to be carefully evaluated to assess their fidelity for tropical cyclone studies.

The paper focuses on the impact of the GCM dynamical core on tropical cyclogenesis in aqua-planet experiments. The dynamical core is the central component of every climate model and determines the numerical schemes, diffusion properties and computational mesh for the resolved fluid flow. In particular, the paper discusses the impact of up to four dynamical cores on idealized tropical cyclones that grow from an initial warm-core vortex seed. The dynamical cores (FV, FV-Cubed, EUL, SLD) are part of NCAR's Community Atmosphere Model CAM and are run with an identical simplified physics parameterization suite. The latter only incorporates bulk surface fluxes for moisture, sensible heat and friction, a planetary boundary layer parameterized by vertical diffusion, as well as large-scale condensation. The research thereby isolates and reveals the influences of the numerical schemes on the evolution of the cyclone.