Evaluating the impact of the CAM 5 dynamical core in idealized tropical cyclone simulations

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. These are mostly unresolved at typical GCM resolutions of about 50-100 km, and still challenged at high resolutions between 12-30 km. Nevertheless, high-resolution GCMs are becoming a tool of choice to evaluate tropical cyclones in current and future climate conditions. Therefore, the physical and dynamical components of a GCM need to be carefully evaluated to assess their fidelity for tropical cyclone studies.

We implement an idealized tropical cyclone test case for high-resolution GCMs in aqua-planet mode with constant sea surface temperatures. The initial conditions are based on an initial vortex seed that is in gradient-wind and hydrostatic balance and intensifies over a 10-day period. The impact of the dynamical core on the evolution of the tropical cyclone is assessed. In particular, we investigate four dynamical cores (FV, EUL, SLD, HOMME) that are part of NCAR's hydrostatic Community Atmosphere Model CAM 5. The research thereby isolates and reveals the influences of the numerical schemes on the evolution of the cyclone.