Improving climate model coupling through a complete mesh representation: a case study with E3SM (v1) and MOAB (v5.x)

Abstract

Abstract. One of the fundamental factors contributing to the spatiotemporal inaccuracy in climate modeling is the mapping of solution field data between different discretizations and numerical grids used in the coupled component models. The typical climate computational workflow involves evaluation and serialization of the remapping weights during the preprocessing step, which is then consumed by the coupled driver infrastructure during simulation to compute field projections. Tools like Earth System Modeling Framework (ESMF) (Hill et al., 2004) and TempestRemap (Ullrich et al., 2013) offer capability to generate conservative remapping weights, while the Model Coupling Toolkit (MCT) (Larson et al., 2001) that is utilized in many production climate models exposes functionality to make use of the operators to solve the coupled problem. However, such multistep processes present several hurdles in terms of the scientific workflow and impede research productivity. In order to overcome these limitations, we present a fully integrated infrastructure based on the Mesh Oriented datABase (MOAB) (Tautges et al., 2004; Mahadevan et al., 2015) library, which allows for a complete description of the numerical grids and solution data used in each submodel. Through a scalable advancing-front intersection algorithm, the supermesh of the source and target grids are computed, which is then used to assemble the high-order, conservative, and monotonicity-preserving remapping weights between discretization specifications. The Fortran-compatible interfaces in MOAB are utilized to directly link the submodels in the Energy Exascale Earth System Model (E3SM) to enable online remapping strategies in order to simplify the coupled workflow process. We demonstrate the superior computational efficiency of the remapping algorithms in comparison with other state-of-the-science tools and present strong scaling results on large-scale machines for computing remapping weights between the spectral element atmosphere and finite volume discretizations on the polygonal ocean grids.

Strategies for conservative and non-conservative monotone remapping on the sphere

“…In the latter case, grid nesting (Harris and Lin, 2014) and adap-tive grids (Jablonowski et al, 2006;Skamarock and Klemp, 1993) have been used to resolve the complex multiscale nature of the atmosphere. Ensuring the accurate interpolation of data between the different component grids in these simulations is crucial to preserving the models' overall accuracy (Slingo et al, 2009;Mahadevan et al, 2020).…”

Benchmarking Regridding Libraries Used in Earth System Modelling

“…MOAB-Tempest Remap [7], which is also written in C++, is used in the energy exascale Earth system model (E3SM) [8], a state-of-the-art Earth system modelling project funded by the Department of Energy (DOE) in the United States. Through Fortran-compatible interfaces, it offers online conservative regridding based on a scalable advancing-front intersection algorithm, which allows to compute the supermesh defined by the intersection of the source and target grid cells.…”

Strategies for Conservative and Non-Conservative Monotone Remapping on the Sphere

“…In the latter case, grid nesting (Harris and Lin, 2014) and adaptive grids (Jablonowski et al, 2006;Skamarock and Klemp, 1993) have been used to resolve the complex multiscale nature of the atmosphere. Ensuring the accurate interpolation of data between the different component grids in these simulations is crucial to preserving the models overall accuracy (Slingo et al, 2009;Mahadevan et al, 2020).…”