Improving tropical cyclone representation in general circulation models through the use of variable resolution
Seminar Room 1, Newton Institute
Modeling of tropical cyclones in General Circulation Models (GCMs) has been a historically difficult task due to issues such as relatively small storm sizes and intense convective processes. However, recent advances in GCM model design coupled with improvements in computing ability now allow for GCM simulations with grid spacings as small as 15-30 km. This presentation evaluates the potential of GCMs at these high horizontal resolutions to simulate tropical cyclones. In particular, we explore a novel variable-resolution mesh approach that allows for high spatial resolutions in areas of interest, such as low-latitude ocean basins where tropical cyclones are prevalent. Such GCM designs with variable-resolution meshes have the potential to become a future tool in weather forecasting as well as for regional climate assessments.
A statically-nested, variable-resolution mesh option has recently been introduced into the National Center for Atmospheric Research (NCAR) Community Atmosphere Model's (CAM) Spectral Element (SE) dynamical core. We present preliminary CAM-SE model simulations using an idealized tropical cyclone test case with a variety of grid sizes and refinement scales. We evaluate the evolution of tropical cyclones initialized at various locations in or near grid scale transition regions. Specific focus is centered on factors crucial to storm cyclogenesis and maintenance such as air-sea interaction and vertical development. In addition to short-term, deterministic tests, we also investigate the performance of multi-resolution meshes in longer-term climate simulations, including attention paid to the dependance of non-seeded tropical cyclone genesis on spatial resolution and the subsequent implications for regional climate modeling within a global modeling framework. We also discuss pot ential computational consequences of using such a setup in either process or climate studies.