Tropical Cyclone Experiments in the Community Atmosphere Model

With the advancement of modern parallel computer architectures, general circulation models (GCMs) are becoming capable of running operationally at higher horizontal resolutions than ever before. At horizontal resolutions of 0.5° (roughly 55 km near the equator) or finer, GCMs have been successful at simulating tropical cyclones in current and future climate conditions. However, there remain many questions concerning the feasibility of GCMs for tropical cyclone assessments. Tropical cyclone characteristics are investigated in idealized and decadal climate simulations using the NCAR supported Community Atmosphere Model CAM 5. In particular, hydrostatic finite-volume (FV) and spectral element (SE) versions of CAM 5.1 are used at a horizontal equatorial grid spacing of approximately 25 km. The idealized simulations are configured in aqua-planet mode and offer a testbed to understand the impact of model design choices on the simulation of tropical cyclones. The decadal climate simulations are configured in a manner similar to the Atmospheric Model Intercomparison Project (AMIP) with prescribed SSTs. The investigation sheds light on the tropical cyclone size, structure and intensity, as well as differences between the idealized and full decadal simulations.