Process-oriented diagnostics of tropical cyclones in global climate models
Characteristics of tropical cyclones (TCs) in global climate models (GCMs) are known to be influenced by details in model configurations, including horizontal resolution and parameterization schemes. Understanding model-to-model differences in TC characteristics is one of the key prerequisites toward reducing uncertainty in future TC activity projections by GCMs. To better understand TC characteristics in GCMs, this study conducts process-level examinations of TC structures in eight different GCM simulations that span a range of horizontal resolutions from 1 to 0.25. A recently developed set of process-oriented diagnostics is used to examine wind and thermodynamic structures of the GCM-simulated TCs.
Results indicate that the wind structures of TCs are more strongly constrained by the horizontal resolutions of the models than are their thermodynamic structures. As expected, the structures of TC circulations, such as the radius of maximum wind (RMW) and the location of maximum vertical velocity, become more realistic with smaller horizontal grid spacing. However, the RMWs are still too large with 0.25 grid spacing, and there are rising motions occurring at the storm center. The distributions of precipitation, moisture, surface turbulent and radiative fluxes around TCs are diverse, even across models with similar horizontal resolutions. When compared across models with similar horizontal resolutions, models that produce greater rainfall in the TC inner-core regions tend to simulate stronger TCs.