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HadGEM3

The HadGEM3-GC31 models use the Global Coupled configuration 3.1 (GC3.1) of the HadGEM3 model (Williams et al., 2017). This model comprises the MetUM atmosphere and JULES land models using Global Atmosphere 7.1 (GA7.1) and Global Land 7.0 (GL7.0) configurations (Walters et al., 2017). These are coupled to the NEMO ocean and CICE sea ice models using the Global Ocean 6.0 (GO6.0, Storkey et al., 2018) and Global Sea Ice 8.1 (GSI8.1, Ridley et al., 2018).

The HadGEM3-GC31-MM model horizontal resolution is N216 for the atmosphere and land and 0.25∘ (ORCA025) for the ocean and sea ice, and the HadGEM3-GC31-LL model horizontal resolution is N96 for the atmosphere and land and 1∘ (ORCA1) for the ocean and sea ice. Both HadGEM3-GC31 models use 85 vertical levels in the atmosphere, and the ocean components use 75 vertical levels.

The sea ice model component is based upon CICE version 5.1.2 (Hunke et al., 2015), with a prognostic ice thickness distribution (ITD) with five thickness categories. The standard CICE elastic–viscous–plastic (EVP) rheology is used for ice dynamics (Hunke et al., 2015). The model uses the Bitz and Lipscomb (1999) multi-layer vertical thermodynamics with four layers of ice and one of snow.

Atmosphere–ice coupling is performed separately for each ice thickness category using the method of West et al. (2016). Radiation is calculated using CICE's “default” CCSM3 scheme (Hunke et al., 2015). Prognostic melt ponds are included using the CICE topographic melt pond formulation of Flocco et al. (2010).

There are several minor differences between the LL and MM resolution versions of HadGEM3-GC3.1, which are displayed in Table 2 of Roberts et al. (2019).

Institution: Met Office Hadley Centre, Exeter, Devon, UK

Model: Hadley Centre Global Earth Model HadGEM-GC31-LL // HadGEM-GC31-MM
Resolution: aerosol: 250 km, atmos: 250 km, land: 250 km, ocean: 100 km, seaIce: 100 km // aerosol: 100 km, atmos: 100 km, land: 100 km, ocean: 25 km, seaIce: 25 km
Components:

HadGEM-GC31-LL: aerosol: UKCA-GLOMAP-mode, atmos: MetUM-HadGEM3-GA7.1 (N96; 192 x 144 longitude/latitude; 85 levels; top level 85 km), land: JULES-HadGEM3-GL7.1, ocean: NEMO-HadGEM3-GO6.0 (eORCA1 tripolar primarily 1 deg with meridional refinement down to 1/3 degree in the tropics; 360 x 330 longitude/latitude; 75 levels; top grid cell 0-1 m), seaIce: CICE-HadGEM3-GSI8 (eORCA1 tripolar primarily 1 deg; 360 x 330 longitude/latitude)

HadGEM-GC31-MM: aerosol: UKCA-GLOMAP-mode, atmos: MetUM-HadGEM3-GA7.1 (N216; 432 x 324 longitude/latitude; 85 levels; top level 85 km), land: JULES-HadGEM3-GL7.1, ocean: NEMO-HadGEM3-GO6.0 (eORCA025 tripolar primarily 0.25 deg; 1440 x 1205 longitude/latitude; 75 levels; top grid cell 0-1 m), seaIce: CICE-HadGEM3-GSI8 (eORCA025 tripolar primarily 0.25 deg; 1440 x 1205 longitude/latitude)

Contact: Tim Andrews, email: timothy.andrews (at) metoffice.gov.uk // Jeff Ridley, email: jeff.ridley (at) metoffice.gov.uk
References: Williams, K. D., et al. , The Met Office Global Coupled model 3.0 and 3.1 (GC3.0 and GC3.1) configurations, J. Adv. Model. Earth Sy., 10, 357-380, 2017, https://doi.org/10.1002/2017MS001115
Information: https://cera-www.dkrz.de/WDCC/ui/cerasearch/cmip6?input=CMIP6.RFMIP.MOHC.HadGEM3-GC31-LL ; https://cera-www.dkrz.de/WDCC/ui/cerasearch/cmip6?input=CMIP6.CMIP.MOHC.HadGEM3-GC31-MM