Topography in ClimaAtmos

• Dataset source: https://www.ncei.noaa.gov/products/etopo-global-relief-model
• ClimaArtifact: https://github.com/CliMA/ClimaArtifacts/tree/main/earth_orography

We use the ClimaUtilities SpaceVaryingInput tool to regrid (using linear interpolation) the ETOPO2022 ice-surface elevation dataset (see ClimaArtifacts) onto the required spectral element horizontal grid. The file examples/topography_spectra.jl provides tools to generate such regridded fields (and their spectra) on user-defined horizontal spaces. For existing ClimaAtmos simulation data, the orog_inst.nc dataset from the default diagnostic outputs contains this regridded elevation.

The regridded Earth elevation is always smoothed by Laplacian diffusion of the surface (Hypsography.diffuse_surface_elevation! in ClimaCore), with the number of diffusion iterations set by the topography_damping_factor configuration argument, and negative elevations clipped to zero. Analytic topographies are smoothed only when topo_smoothing is set. The smoothed surface is extended into the interior by the vertical mesh warp selected with mesh_warp_type (SLEVE, the default, or Linear).

As an example, we include plots of the generated topography on a cubed sphere with 16 elements and 64 elements per panel edge, and compare unsmoothed and smoothed datasets to show the effect of this smoothing.

• Elevation data (elems per panel = 16)

• Elevation data (elems per panel = 64)