GCHP horizontal grids

GCHP uses cubed-sphere horizontal grids instead of the traditional cartesian grids. For a good general description of cubed sphere grids, please see our Cubed-sphere grid illustrations page at geos-chem.org.

Cubed-sphere grid resolutions are denoted using the number of grid cells along each face. At present GCHP uses grids with 72 vertical layers, but this may increase to 132 layers in the near future.

The table below shows some common cubed-sphere configurations.

Grid	# cells per face	# cells at surface	# layers	# cells total	# Equiv. lat-lon grid
C24	24	3456	72	248,832	4° x 5°
C30	30	5400	72	388,800	4° x 5°
C48	48	13,824	72	995,328	2° x 2.5°
C90	90	48,600	72	3,499,200	1° x 1.25°
C180	180	194,400	72	13,996,800	0.5° x 0.625°
C360	360	777,600	72	55,987,200	0.25° x 0.3125°
C720	720	3,110,400	72	223,948,800	0.125° x 0.15625°

The default GCHP grid resolution is C90. Users are encouraged to think carefully about their run’s needs and available resources when choosing a grid resolution. Higher-resolution simulations provide a more faithful representation of transport [Strahan and Polansky, 2006], as the model can better resolve nonlinearities and heterogeneity, albeit at greater computational expense. Current GCHP applications commonly span within C48 to C360. Determing a “sufficient” model resolution is highly dependent on your exact research question.

Switching from C24/30/48 to C90 or higher will require some changes to your run configuration, as the computational cost of running GCHP increases with grid resolution.

See our Stretched-Grid Simulation chapter for information about how you can stretch one of the grid faces to achieve extra-fine resolution over a target location.

Reference: Eastham et al. [2018]