Enable Copernicus DEM #427
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One point could be optimised/simplified in the future (if needed & resources are available): Copernicus DEM data comes with a reduced longitudinal resolution towards higher latitudes (see https://dataspace.copernicus.eu/sites/default/files/media/files/2024-06/geo1988-copernicusdem-spe-002_producthandbook_i5.0.pdf). Currently, this data is interpolated to a latitude-longitude grid with uniform spacing of 1/3600 degrees so that the data can be processes in EXTPAR analogous to GLOBE, ASTER and MERIT data. However, when topography data is remapped to the ICON grid in EXTPAR, elevation data of longitudinal rows is aggregated before remapping. This unnecessary back and forth interpolation could be eliminated, which would also result in a considerable smaller memory usage of the Copernicus DEM... |
src/mo_agg_sgsl.f90
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| ndata(ie,je,ke) = ndata(ie,je,ke) + 1 | ||
| sgsl(ie,je,ke) = sgsl(ie,je,ke) + sl(i) |
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| ndata(ie,je,ke) = ndata(ie,je,ke) + 1 | |
| sgsl(ie,je,ke) = sgsl(ie,je,ke) + sl(i) | |
| ndata(ie,je,ke) = ndata(ie,je,ke) + 1 | |
| sgsl(ie,je,ke) = sgsl(ie,je,ke) + sl(i) |
Also, could you do me a favor and apply the same changes to the cases above? 🙂
src/mo_agg_topo_cosmo.f90
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| h22(ie,je,ke) = h22(ie,je,ke) + dhdydy(i) | ||
| ENDIF | ||
| ENDIF | ||
| CASE(topo_copernicus) |
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Unless you have a reason to add this code here I think we could just skip it, since COSMO is not really used anymore and I will probably start to remove COSMO related code at some point.
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Done - I removed the implementation of Copernicus DEM for COSMO.
src/mo_topo_data.f90
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| half_gridp = 1./(3600.*2.) ! the resolution of the ASTER data is 1./3600. degrees as it is half a grid point | ||
| ! it is additionally divided by 2 | ||
| CASE (topo_gl) ! GLOBE topography is composed of 16 tiles | ||
| half_gridp = 1./(3600.*2.) |
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Why remove these comments?
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I thought the comment is unnecessary because it's easy inferable from the code what is done here. But I guess it's also fine to leave it (I reintroduced it in a more concise way).
| tiles_lon_max(i) = REAL(NINT(tiles_lon_max(i) + half_gridp)) !< added, as the ASTER/GLOBE/MERIT data | ||
| tiles_lat_min(i) = REAL(NINT(tiles_lat_min(i) + half_gridp)) !< is located at the pixel center | ||
| tiles_lat_max(i) = REAL(NINT(tiles_lat_max(i) - half_gridp)) | ||
| SELECT CASE (itopo_type) |
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Let's actually merge that one first.
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Yes, that's true. But this specific modification is also needed for Copernicus DEM to run correctly. If one would merge the current master (including the branch grid_shift_topo) into this branch, the single difference should be the line
CASE(topo_merit, topo_copernicus) ! edges of raw data tiles do not align with integer coordinates
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In general, I think now you are only missing the new tests for Copernicus (if you want to also add the ICON ones for ASTER we can do it in a separate PR) and the update to the docs. I recently added a new PR template, maybe this can be useful for you as well. I will post it here, since this PR was opened before the template was made. |
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Enables the usage of Copernicus DEM (30 m resolution) as input topography data for EXTPAR.
https://dataspace.copernicus.eu/explore-data/data-collections/copernicus-contributing-missions/collections-description/COP-DEM
Copernicus DEM is a high-resolution (30 m) topography data set, which is based on recent satellite data. Its superior accuracy compared to other DEMs was demonstrated in various publications (e.g., Guth (2021)). It is particular useful as a replacement for ASTER data for high-resolution simulations (~1km grid spacing and smaller) and for regions with complex terrain (ASTER data reveals, for instance, some distinctive artifacts in the Alps - particularly at steep north-facing slopes). Another benefit compared to ASTER is its global coverage.
The added run script (last commit) was used for testing - I'm not sure if it is necessary to merge it as run scripts will no longer be maintained at some point in the near future...
References:
Guth, P. L. and Geoffroy, T. M. (2021). LiDAR point cloud and ICESat-2 evaluation of 1 second global digital elevation models: Copernicus wins. Transactions in GIS, 25, 2245–2261.