Using a two-stage Rosenbrock solver to increase computational efficiency in the DOE's Exascale Earth System Model version 1 (E3SMv1)
- 1University of Tennessee at Knoxville (Knoxville, United States of America)
Abstract
The integration of stiff atmospheric chemical systems is a major computational cost in Earth System Models and poses challenges for numerical stability as chemical complexity and temporal resolution increase. In this study, we implement a semi-implicit two-stage Rosenbrock method (ROS2) in the Energy Exascale Earth System Model version 1 (E3SMv1) and evaluate it as an alternative chemistry time-integration scheme. ROS2 is tested with two interactive chemical mechanisms of substantially different size: chemUCI (60 prognostic species) and trop_strat_mozart_mam4 (155 prognostic species). Numerical experiments include short simulations to quantify computational cost, a box-model timestep-refinement analysis, and one-year integrations to examine numerical stability and solution sensitivity. At the same 180 s chemistry timestep, ROS2 requires approximately 33 % less chemistry integration time than the original iterative implicit solver on the tested Cori/KNL CPU platform. The magnitude of this speedup is configuration dependent. Global-mean surface-ozone differences among the tested configurations are small (≤ 1.03 ppb), and the one-year integrations show no evidence of numerical instability. Spatial and diurnal differences in ozone, NO, NO ₂ , and OH are species- and mechanism-dependent, indicating sensitivity to both timestep and solver formulation rather than a common systematic bias. These results support ROS2 as a lower-cost alternative to the current implicit integrator when E3SM chemistry is operated at short timesteps; additional timestep-refinement tests and benchmarking on contemporary CPU/GPU systems are needed to quantify coupled-model convergence and performance portability.
Versions
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BibTeX
@article{chien2026using,
title = {{Using a two-stage Rosenbrock solver to increase computational efficiency in the DOE's Exascale Earth System Model version 1 (E3SMv1)}},
author = {Rong-You Chien and Joshua S. Fu},
journal = {Geoscientific Model Development},
year = {2026},
month = oct,
doi = {10.5194/gmd-19-10309-2026},
url = {https://gmd.copernicus.org/articles/19/10309/2026/},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Using a two-stage Rosenbrock solver to increase computational efficiency in the DOE's Exascale Earth System Model version 1 (E3SMv1)
AU - Rong-You Chien
AU - Joshua S. Fu
PY - 2026
DA - 2026/10/29
JO - Geoscientific Model Development
DO - 10.5194/gmd-19-10309-2026
UR - https://gmd.copernicus.org/articles/19/10309/2026/
AB - The integration of stiff atmospheric chemical systems is a major computational cost in Earth System Models and poses challenges for numerical stability as chemical complexity and temporal resolution increase. In this study, we implement a semi-implicit two-stage Rosenbrock method (ROS2) in the Energy Exascale Earth System Model version 1 (E3SMv1) and evaluate it as an alternative chemistry time-integration scheme. ROS2 is tested with two interactive chemical mechanisms of substantially different size: chemUCI (60 prognostic species) and trop_strat_mozart_mam4 (155 prognostic species). Numerical experiments include short simulations to quantify computational cost, a box-model timestep-refinement analysis, and one-year integrations to examine numerical stability and solution sensitivity. At the same 180 s chemistry timestep, ROS2 requires approximately 33 % less chemistry integration time than the original iterative implicit solver on the tested Cori/KNL CPU platform. The magnitude of this speedup is configuration dependent. Global-mean surface-ozone differences among the tested configurations are small (≤ 1.03 ppb), and the one-year integrations show no evidence of numerical instability. Spatial and diurnal differences in ozone, NO, NO ₂ , and OH are species- and mechanism-dependent, indicating sensitivity to both timestep and solver formulation rather than a common systematic bias. These results support ROS2 as a lower-cost alternative to the current implicit integrator when E3SM chemistry is operated at short timesteps; additional timestep-refinement tests and benchmarking on contemporary CPU/GPU systems are needed to quantify coupled-model convergence and performance portability.
SN - 1991-9603
ER -