Flow-following, finite-volume Icosahedral Model

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

The FIM is being developed as a candidate to eventually supplant the Global Forecast System, the United States's current medium-range forecast model. The FIM was originally slated to become operational some time in 2014 (as of spring 2016 the model is still testing); the GFS will continue to be run and maintained for several years afterward, much in the same way the GFS and its predecessor, the Nested Grid Model, ran concurrently for several years. The model currently produces similar results to the GFS, but runs slower on the NWS's operational computers. Its three-part name derives from its key features: "flow-following" indicates that its vertical coordinates are based on both terrain and potential temperature (isentropic sigma coordinates, previously used in the now-discontinued rapid update cycle model), and "finite-volume" describes the method used for calculating horizontal transport. The "icosahedral" portion describes the model's most 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 runs as a multiscale model, with a suffix number indicating the model's horizontal resolution. FIM7 operates at a spatial resolution of approximately 60 km, FIM8 at 30 km, FIM9 at 15km and FIM9.5 at 10km. The FIM7 and FIM8 both run twice daily (0z and 12z) with 6-hour temporal resolution out to 14 days. The FIM9 runs four times daily, also with 6-hour steps, out to 7 days. (FIM9.5 is not currently in operation.)

External links

Official FIM Web site, includes forecasts and documentation

Atmospheric, oceanographic and climate models

Model types

Atmospheric model Climate model Numerical weather prediction Tropical cyclone forecast model Atmospheric dispersion modeling Chemical transport model Upper-atmospheric models Ensemble forecasting Model output statistics Meteorological reanalysis Parametrization

Specific models

Climate	IGCM HadCM3 HadGEM1 GFDL CM2.X CGCM CCSM CFSv2 ECHAM MPAS

Global weather	IFS (ECMWF) FIM GEM GFS NAVGEM UM JMA GME ARPEGE

Regional and mesoscale atmospheric	NAM RR / RAP RAMS WRF RAQMS HIRLAM LAPS RPM

Regional and mesoscale oceanographic	HyCOM ROMS POM MOM FVCOM MITgcm

Atmospheric dispersion	ADMS AERMOD ATSTEP AUSTAL2000 CALPUFF DISPERSION21 ISC3 MEMO MERCURE NAME OSPM PUFF-PLUME RIMPUFF SAFE AIR

Chemical transport	CLaMS MOZART GEOS-Chem

Land surface parametrization	JULES CLASS ISBA

Discontinued	AVN / MRF / GSM Eta LFM MM5 NGM NOGAPS RUC

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