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f67abf1ee3 Jeff*0001 Global atmosphere: ‘Held-Suarez’ benchmark
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0003
0004
0005 A novel feature of MITgcm is its ability to simulate, using one basic algorithm,
0006 both atmospheric and oceanographic flows at both small and large scales.
0007
0008 :numref:`cubic_eddies_figure` shows an instantaneous plot of the 500 mb
0009 temperature field obtained using the atmospheric isomorph of MITgcm run at
0010 2.8° resolution on the cubed sphere. We see cold air over the pole
0011 (blue) and warm air along an equatorial band (red). Fully developed
0012 baroclinic eddies spawned in the northern hemisphere storm track are
0013 evident. There are no mountains or land-sea contrast in this calculation,
0014 but you can easily put them in. The model is driven by relaxation to a
0015 radiative-convective equilibrium profile, following the description set out
0016 in Held and Suarez (1994) :cite:`held-suar:94` designed to test atmospheric hydrodynamical cores -
0017 there are no mountains or land-sea contrast.
0018
0019
0020 .. figure:: figs/eddy_on_cubic_globe.*
0021 :width: 60%
0022 :align: center
0023 :alt: cubic eddies figure
0024 :name: cubic_eddies_figure
0025
0026 Instantaneous plot of the temperature field at 500 mb obtained using the atmospheric isomorph of MITgcm
0027
0028
0029 As described in Adcroft et al. (2004) :cite:`adcroft:04b`, a ‘cubed sphere’ is used to discretize the
0030 globe permitting a uniform griding and obviated the need to Fourier filter.
0031 The ‘vector-invariant’ form of MITgcm supports any orthogonal curvilinear
0032 grid, of which the cubed sphere is just one of many choices.
0033
0034 :numref:`hs_zave_u_figure` shows the 5-year mean, zonally averaged zonal
0035 wind from a 20-level configuration of
0036 the model. It compares favorable with more conventional spatial
0037 discretization approaches. The two plots show the field calculated using the
0038 cube-sphere grid and the flow calculated using a regular, spherical polar
0039 latitude-longitude grid. Both grids are supported within the model.
0040
0041 .. figure:: figs/u_cube_latlon_comb.*
0042 :width: 80%
0043 :align: center
0044 :alt: hs_zave_u_figure
0045 :name: hs_zave_u_figure
0046
0047 Five year mean, zonally averaged zonal flow for cube-sphere simulation (top) and latitude-longitude simulation (bottom) and using Held-Suarez forcing. Note the difference in the solutions over the pole — the cubed sphere is superior.
0048
