Flow-following, finite-volume Icosahedral Model: Difference between revisions

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The '''Flow-following, finite-volume Icosahedral Model''' (FIM) is a [[numerical weather prediction]] model currently under development at the [[Earth System Research Laboratory]].

The FIM is intended to eventually supplant the [[Global Forecast System]], the United States's current medium-range forecast model, when operational (this was originally estimated to be some time around 2014). The model is expected to greatly improve on the GFS, which has historically performed more poorly than its rival models from other countries (particularly the [[Global Environmental Mesoscale model|GEM]] and [[Integrated Forecast System|IFS]]). Its three-part name derives from its key features: "flow-following" indicates that its vertical coordinates follow [[isentrope]]s, and "finite-volume" describes the method used for calculating horizontal transport. The "icosahedral" portion describes the model's uniquemost uncommon feature: whereas most grid-based forecast models have historically used rectangular grid points (a less than ideal arrangement for a planet that is a slightly [[oblate spheroid]]), the FIM instead fits Earth to a [[truncated icosahedron]], with twelve evenly spaced pentagons (including two at the poles) anchoring a grid of hexagons.

The FIM is currently being run at resolutions of 10, 15, 30 and 60 kilometers. When being run regularly, the models run twice daily, with forecasts issued in six-hour intervals out to 14 days (only at the 30 km scale; the other resolutions only run out 7 to 10 days).