Toward Ultrahigh-Resolution E3SM Land Modeling on Exascale Computers

We present an ultrahigh-resolution Energy Exascale Earth System Model Land Model (uELM) for high-fidelity land simulations targeting new exascale computers. After considering modeling infrastructure compatibility and ELM software features, we designed a parallel model for the uELM development targeting the hybrid architectures of new U.S. exascale computers. We also described a function unit test framework to expedite the piecewise code porting (with compiler directives), verification, and global variable management. Furthermore, in this study, we report the development of an early uELM model using OpenACC within a function unit test framework on a pre-exascale computer, demonstrate the performance of a uLEM submodel with three-times speedup, and summarize the code-porting experience regarding global variable handling, deepcopy, memory reduction, and parallel loop reconstruction.