As part of the efforts in the CMDV project, interfaces to integrate the MOAB unstructured mesh library with the TempestRemap remapping tool have been undertaken. Detailed information on the algorithmic and implementation aspects of this effort have been written in a manuscript submitted to Geoscientific Model Development [1]. This work has led to the development of a new offline remapping tool called mbtempest, which exposes the functionality to compute the supermesh or intersection mesh between two unstructured source and target component grids, in addition to using this supermesh for computing the remapping weights to project solutions between the grids. This functionality is part of the critical worflow with E3SM, where the generated remapping weights in the offline step are consumed by MCT at runtime to seamlessly transfer solution data between components (atm↔ocn, atm↔lnd, etc).
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Getting started
In order to build the MOAB-TempestRemap stack with parallel MPI launch support, we suggest the following list of commands. First define an installation prefix directory where the stack of library, includes and tools will be installed. Let us call this as the $INSTALL_PREFIX environment variable.
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The first -l option specifies the source grid to load, and the second -l option specifies the target grid to load. mbtempest can load Exodus, .nc and h5m files in serial, while the parallel I/O is generally optimized only for the native HDF5 format (h5m). So we recommend converting meshes to this format and pre-partitioning using the instructions above.
Generating remapping weights in parallel
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We are currently working on a Python script to convert the MOAB h5m file to a SCRIP file to be consumed in E3SM directly. As a future task, we will also be investing effort into writing a SCRIP file in parallel through a custom I/O interface using PNetCDF.
References
1 Mahadevan, V. S., Grindeanu, I., Jacob, R., and Sarich, J.: Improving climate model coupling through a complete mesh representation: a case study with E3SM (v1) and MOAB (v5.x), Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2018-280, in review, 2018.