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TempestRemap

Author: Paul Ullrich Email: [email protected]

Copyright (c) 2017, Paul Ullrich All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright
  notice, this list of conditions and the following disclaimer.
  
* Redistributions in binary form must reproduce the above copyright
  notice, this list of conditions and the following disclaimer in the
  documentation and/or other materials provided with the distribution.
  
* Neither the name of TempestRemap nor the names of its contributors may
  be used to endorse or promote products derived from this software without
  specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Overview

This software constitutes the beta release of TempestRemap, a conservative, consistent and monotone remapping package for arbitrary grid geometry with support for finite volumes and finite elements. There is still quite a bit of work to be done, but any feedback is appreciated on the software in its current form.

If you choose to use this software in your work, please cite our papers:

Paul A. Ullrich and Mark A. Taylor, 2015: Arbitrary-Order Conservative and Consistent Remapping and a Theory of Linear Maps: Part 1. Mon. Wea. Rev., 143, 2419–2440, doi: 10.1175/MWR-D-14-00343.1

Paul A. Ullrich, Darshi Devendran and Hans Johansen, 2016: Arbitrary-Order Conservative and Consistent Remapping and a Theory of Linear Maps, Part 2. Mon. Weather Rev., 144, 1529-1549, doi: 10.1175/MWR-D-15-0301.1.

Build Instructions

The software can be obtained from the GITHub repository via git:

git clone https://github.com/paullric/tempestgecore.git

You will likely need to edit the first couple lines of the Makefile to customize the NetCDF paths and change any compiler flags. Once you have modified the Makefile, build the code:

make all

Mesh Generation

The remapping process requires multiple stages. First you will need an Exodus file (file extension .g) for your input mesh and your output mesh. This can either be done via the SQuadGen mesh utility, or via the three GenerateMesh executables that come with TempestRemap.

For a cubed-sphere mesh:

./GenerateCSMesh --res --alt --file .g

For a latitude-longitude mesh:

./GenerateRLLMesh --lon --lat --file .g

For a geodesic mesh:

./GenerateICOMesh --res --dual --file .g

Once your input and output meshes are generated, you will need to generate the overlap mesh (that is, the mesh obtained by placing the input and output mesh overtop one another and recalculating intersections). This can be done as follows:

./GenerateOverlapMesh --a .g --b .g --out .g

Offline Map Generation

Once the overlap mesh is generated, you can now generate the weight file, which the contains information on remapping from one mesh to the other. The type of offline map desired is specified by --in_type and --out_type, which can be one of the following:

fv - Finite volume mesh, with degrees of freedom stored as volume averages cgll - Continuous finite element method (such as spectral element) dgll - Discontinuous finite element method (such as discontinuous Galerkin)

Offline map generation is then performed as follows:

For finite volume to finite volume remapping:

./GenerateOfflineMap --in_mesh .g --out_mesh .g --ov_mesh .g --in_np --out_map .nc

Monotone remapping in this case can be achieved with --in_np 1.

For finite element to finite volume remapping:

./GenerateOfflineMap --in_mesh .g --out_mesh .g --ov_mesh .g --in_type [cgll|dgll] --out_type fv --in_np --out_map .nc

Monotone remapping in this case can be achieved with argument --mono.

For finite volume to finite element remapping:

./GenerateOfflineMap --in_mesh .g --out_mesh .g --ov_mesh .g --in_type fv --out_type [cgll|dgll] --in_np --out_np --out_map .nc

Monotone remapping in this case requires --mono and --in_np 1.

For finite element to finite element remapping:

./GenerateOfflineMap --in_mesh .g --out_mesh .g --ov_mesh .g --in_type [cgll|dgll] --out_type [cgll|dgll] --in_np --out_np --out_map .nc

Monotone remapping in this case requires --in_np 1 and --out_np 1.

In each case, the linear weights file will then be written to .nc in SCRIP format (although it’s a bare-bones version of SCRIP format at the moment and I’m not sure it’ll work with SCRIP utilities). Now that the map is generated you can apply it to your data files:

Offline Map Application

The offline map can be applied using the ApplyOfflineMap utility:

./ApplyOfflineMap --map .nc --var --in_data .nc --out_data .nc

The remapped fields should then appear in .nc. Note that if your output mesh is rectilinear, such as a latitude-longitude mesh, the data will automatically be arranged with horizontal spatial dimensions lat and lon.

Summary

Please let me know if you have any problems / bugs / comments / feature requests.