The Structure and Evolution of Extratropical Cyclones, Fronts, Jet Streams, and the Tropopause in the GEOS General Circulation Model
Abstract The realism of extratropical cyclones, fronts, jet streams, and the tropopause in the Goddard Earth Observing System (GEOS) general circulation model (GCM), implemented in assimilation and simulation modes, is evaluated from climatological and case–study perspectives using the GEOS–1 reanalysis climatology and applicable conceptual models as benchmarks for comparison. The latitude–longitude grid spacing of the datasets derived from the GEOS GCM ranges from 2° × 2.5° to 0.5° × 0.5°. Frontal systems in the higher–resolution datasets are characterized by horizontal potential temperature gradients that are narrower in scale and larger in magnitude than their lower–resolution counterparts, and various structural features in the Shapiro–Keyser cyclone model are replicated with reasonable fidelity at 1° × 1° resolution. The remainder of the evaluation focuses on a 3–month Northern Hemisphere winter simulation of the GEOS GCM at 1° × 1° resolution. The simulation realistically reproduces various large–sc...