{{Refimprove|date = August 2015}}The Reading '''Reading Intermediate General Circulation Model''' ('''IGCM'''), is a simplified or "intermediate" [[Global climate model]], which is developed by members of the [http://www.reading.ac.uk/meterology Department of Meteorology] at the [[University of Reading]], and by members of the [http://www.meteo.mcgill.ca/bourqui/ Stratospheric Dynamics and Chemistry Group] of the [[McGill Atmospheric and Oceanic Sciences|Department of Atmospheric and Oceanic Sciences]] at [[McGill University]].
The IGCM is a fast [[Global climate model|GCM]] based on the primitive-equations [[Baroclinity|baroclinic]] model of Hoskins and Simmons, which has been converted to run on workstations. Several versionsvariations have been developed withby adjusting representations of the physics.
* IGCM1: Portable version of the original spectral, dry baroclinic model formulated in sigma-levels, with an option for [[data assimilation|Newtonian relaxation]] and [[Rayleigh]] friction, with no surface.
* IGCM2: Includes simplified moist parameterisations, a cheap "radiation scheme" (i.e. constant tropospheric cooling), a bulk formulation scheme for the boundary layer, fixed surface temperatures and humidity, a uniform vertical diffusion, and can [[Advection|advect]] tracers.
* IGCM3x: Intermediate climate model whichthat includes more sophisticated moist moisture/clouds parameterisations, a radiation scheme with various gas absorbers, and a more realistic surface with an [[orography]] and land, and sea surface schemes.
The [[Adiabatic process|adiabatic]] version, IGCM1, is freely available. Access to IGCM2 and IGCM3 is restricted to members of the Department of Meteorology at the University of Reading and collaborating researchers.
