v3/v4 Campaign Goals

Targeted for use in Phase III, E3SM versions v3 and v4 will feature notable developments in advancing the fully-coupled E3SM to answer the more demanding questions in the corresponding science campaigns. Advancing better simulations requires the performance expected from the 100 PFLOP and Exascale systems planned for DOE centers. Since the developments for the v3 and v4 model are longer-term and higher risk, they require less day-to-day oversight and management than the Core activities with nearer-term deliverables. Nevertheless, the research does target inclusion of new developments into the modeling system within five years, so they are not open-ended.

The v3/v4 science questions focus on addressing uncertainty in predicting future changes in water cycle, biogeochemistry, and cryosphere systems. To address the science questions, the four large Next Generation Development subprojects and two smaller research tasks that will advance the E3SM Project toward its v3 and v4 objectives (see NGD Sub-Projects)

v3/v4 Science Questions

The v3 science campaign will continue to focus on advancing understanding and modeling of water cycle, biogeochemistry, and cryosphere systems (along with their response to perturbations). However, an equally strong focus will be on exploring uncertainties and their sources in Earth system simulations, which is critical for building a strong foundation for the use of E3SM for hypothesis testing and credible simulations and predictions. This necessitates major efforts to represent processes that are currently not included or poorly represented in E3SM to evaluate their contributions to model uncertainty.  The science questions are used to guide the strategic development of E3SM v3/v4 through the NGD sub-projects.

Water Cycle


What are the moisture sources for precipitation over land? Do models converge with increasing resolution, and what controls this behavior? How will the moisture sources and precipitation over land change in the future?

To reveal the mechanisms for the resolution sensitivity and implications to projecting future changes in land precipitation, new modeling capabilities are needed to support the v3/v4 water cycle science campaign. A required feature for E3SM v3/v4 is a nonhydrostatic atmospheric dynamical core that allows convection permitting simulations coupled to an eddy-resolving ocean, and a land component with an advanced subgrid hierarchical structure to capture land surface heterogeneity. With this modeling system, simulations will be performed at horizontal resolutions ranging from a few to 100 kilometers for atmosphere and land to disentangle the various mechanisms contributing to the resolution sensitivity of water cycle simulations. Possible convergence will be explored, with resolution at grid spacing that is much beyond what have been attempted in previous modeling studies. Bypassing the need for cumulus parameterizations at grid spacing of a few kilometers, simulations may capture organized convection that is a major driver of large-scale circulation and precipitation.

Both atmosphere-only and coupled simulations will be performed for the present climate to quantify and diagnose the resolution sensitivity. These simulations will be configured with different combinations of resolutions for the atmosphere, ocean, and land components that aim to more systematically explore the resolution parameter space across Earth system components. Informed by the resolution experiments, coupled simulations for historical and future climate will be performed with configurations and resolutions that capture the key sensitivity-dependent behavior to investigate its implications to projecting future changes in land precipitation, aridity, floods, and droughts. These experiments will contribute to furthering our understanding of future water cycle changes and projection uncertainty.



What are the impacts of different energy and land use on the biogeochemical cycle and water availability? How might terrestrial-aquatic processes influence terrestrial and marine biogeochemistry?

In the v3 science campaigns, the v2 biogeochemistry focus will be extended to include processes such as terrestrial-aquatic processes that are not represented in the v1 or v2 model to explore the implications of different energy and land use pathways on the carbon cycle, and evaluate the broader impacts on water availability and climate through vegetation dynamics, linkages between land and water use, and potential changes in aerosols that provide climate feedbacks. Perturbations from climate, particularly related to changes in heavy rainfall and rapid snowmelt—as well as land use and land management practices—could alter carbon inputs to the rivers, and subsequent carbon fluxes across the terrestrial-aquatic interface that influence ocean carbon cycle. Complementary to investigations of carbon cycle, the project will also explore the impacts of methane emission reduction (in the context of the natural methane sources and sinks) to address a broader question of the implications of different energy and land use futures.

Modeling experiments with and without coupling of E3SM with an integrated assessment model (the Global Change Assessment Model, GCAM) will be performed for selected carbon pathways featuring high fossil fuel vs. high renewable energy scenarios and methane emission levels to explore the interactions between land use, water use and the role of human-Earth interactions. More detailed U.S.-relevant scenarios will also be developed, particularly for simulations with regional refinement at high resolution over the U.S. Sensitivity experiments will contrast the impacts of different energy and land use pathways and isolate the effects of land and water management on the land carbon sink and water deficit. These experiments will also evaluate the impacts of radiative forcing (e.g., increased aridity and droughts) on the ability to achieve different energy and land use futures and explore uncertainty and effects of carbon processes in the land-ocean-aquatic continuum and potential impacts on the effectiveness of the emissions scenarios and carbon pathways.

Cryosphere Systems


What processes and their model representations contribute to key uncertainties in projecting regional sea level rise? What are the implications to coastal inundation that result from interactions between sea level rise and extreme storms?

Critical model capabilities to address our science questions include improving representations of calving of ice shelves, subglacial hydrology, water mass transformation and new ocean water for modeling of the Antarctic Ice Sheet, improved modeling of snow on sea ice to better simulate sea ice loss, coastal ocean and wave modeling for simulation of storm surge, and inundation dynamics. These are partly being developed by the SciDAC4 project and will be made available to E3SM. Guided by process understanding, diagnosis of v1 and v2 model errors, and assessment of the impacts of new processes in the v3 model, a large number of offline ocean-ice simulations in combination with coupled simulations will be performed to disentangle the relative importance of different sources of uncertainty and diagnose the nonlinear process interactions across Earth system components. With an experimental design informed by the uncertainty analysis, simulations will be performed to understand the coastal impacts of regional SLR.

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