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High resolution USGS topography file named USGS-topo-cube3000.nc (located in the CESM inputdata server here; note this is on a 3 km cubed sphere grid)
SCRIP-format atmosphere grid file
topography tool (
components/cam/tools/topo_tool/cube_to_target)homme_tool (same tool used to create SCRIP files described above).
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Steps (a) and (c) use the topography tool located at components/cameam/tools/topo_tool/cube_to_target in the E3SM repo. This requires the SCRIP dualgrid file which can be computed with homme_tool.
Step (b) requires running the homme_tool's smoothing algorithm. The namelist should be edited to specify the resolution (NE value) or grid file (RRM) grid and the amount of smoothing
(TODO: allow running this script with command line arguments instead of manual editing so that the task can be automated). Detailed instructions depend on which version of the model is being used:
E3SM V1. V1 Topography: GLL grids
V1 uses topography on a GLL grid with a laplacing smoothing. The smoothing reduces the effective resolution of the topography from 2dx to 6.4dx. (effective resolution is determined by the first wavelength to be damped by 50% from the unsmoothed topography, computed via spherical harmonic spectra)
V1 only needs data on the GLL grid.
Tool chain: V1 Topography: GLL grids Requires cube_to_target, homme_tool, and a SCRIP file for the grid.
V1 has poor treatment of topography and compensates in part with increased divergence damping.
E3SM V2:V2 Topography: GLL/PG2 grids
V2 needs topography on the GLL grid, and then a consistent topography on the PG2 grid (created with the same GLL->PG2 algorithm used internally when running EAM)
V2 uses the same smoothing as V1: 50% damping of the 6.4dx wavelength.
Tool chain: V2 Topography: GLL/PG2 grids
V2 has improved topography treatment over V1. V2 configurations do not need to run with increased divergence damping.
E3SM V3
V3 needs topography on the GLL grid, and then a consistent topography on the PG2 grid (created with the same GLL->PG2 algorithm used internally)
V3 has improved pressure gradient and viscosity treatment over V2 and will be using a significantly rougher topography.
This tool chain has not been finalized yet.The (proposed) V3 tool chain is similar to V2, with minor modifications to in the smoothing algorithm.
V3 has further improved topogrpahy treatments over V2, supporting significantly rougher topography ( /wiki/spaces/NGDNA/pages/2411397876 )
: V3 Topography: GLL/PG2 grids