Idealized Tropical Cyclones in Atmospheric General Circulation Models

The paper discusses the design of idealized tropical cyclone experiments in Atmospheric General Circulation Models (GCMs). Our first goal is to suggest the evolution of an idealized tropical cyclone as a standard test case for atmospheric model developments that adds complexity to a dynamical-core and GCM test suite. In addition, we plan on using idealized cyclones as a test bed for hurricane-dust interactions in the Atlantic Ocean Basin and climate-hurricane sensitivity studies. A group of sensitivity tests will be presented using the National Center for Atmospheric Research's (NCAR) Community Atmosphere Model (CAM) 3.1. The tests are run in a so-called aqua-planet configuration that consists of an ocean-covered Earth with prescribed sea surface temperatures and radiative forcing. We utilize the CAM 3.1 Finite Volume dynamical core on a latitude-longitude grid at a half-degree horizontal resolution. The development of an idealized, initially weak warm-core vortex is investigated with varying initial parameters including vorticity, radius of maximum wind, latitude, and sea surface temperature. The evolution of the initial vortex is especially sensitive to the initial vorticity, and therefore the initial wind speed, and radius of maximum wind. This sensitivity is also related to the model resolution. Although model resolution has improved greatly over the last decade, improved resolution will still be needed to model tropical cyclones in global climate models. These sensitivity tests provide us with suitable initial parameter configurations to model tropical cyclogenesis in CAM 3.1 and other GCMs.