CNES Earth Mean Dynamic Topography
Geodynamics studies have an interest in the Earth’s Mean Dynamic Topography (MDT). CNES has provided such a grid (Jousset_et_al., 2022) post-processed by IGPP.
Usage
You access a global MDT grid by specifying the special name
@earth_mdt[_rru[_reg]]
The following codes for rru and the optional reg are supported (dimensions are listed for pixel-registered grids; gridline-registered grids increment dimensions by one):
Code |
Dimensions |
Reg |
Size |
Description |
|---|---|---|---|---|
01d |
360 x 180 |
g,p |
82 KB |
1 arc degree global MDT (MDT @ 315 km) |
30m |
720 x 360 |
g,p |
241 KB |
30 arc minute global MDT (MDT @ 157 km) |
20m |
1080 x 540 |
g,p |
489 KB |
20 arc minute global MDT (MDT @ 105 km) |
15m |
1440 x 720 |
g,p |
810 KB |
15 arc minute global MDT (MDT @ 79 km) |
10m |
2160 x 1080 |
g,p |
1.6 MB |
10 arc minute global MDT (MDT @ 52 km) |
07m |
2881 x 1441 |
g |
2.7 MB |
7.5 arc minute global MDT (original) |
See GMT remote dataset usage for when resolution codes are optional or required.
All of these data will, when downloaded, be placed in your ~/.gmt/server directory, with
the earth_mdt files being placed in an earth/earth_mdt sub-directory. If you do not
specify a CPT, the default CPT for this dataset (the GMT master @earth_mdt CPT) will be used.
Technical Information
The 10m and lower resolutions are all derivatives of the original 7.5 arc-minute mdt_cnes_cls22_fg.nc grid We scale and reformat the original data to take up very little space so that downloads from the servers are as fast as possible. We have downsampled it via Cartesian Gaussian filtering to prevent aliasing while preserving the latitude-dependent resolution in the original 7.5 arc-minute grid. For the MDT grid this means we chose 0.0001 m as the smallest data unit, which is well below the uncertainties in the model. Data are scaled and shifted to fit in a short integer grid that is highly compressed by netCDF lossless compression and chunking. The data are reported in meters.