Summary

First release of version 2.0 of the Energy Exascale Earthy System Model contains the following changes from v1.0

EAM

The atmosphere component remains EAM. Major changes since version 1 include:

• all column-physics parameterizations are computed on a separate grid that has approximately half the number of points of the dynamics grid

• a new nonhydrostatic dynamical core (running in hydrostatic mode) with semi-Lagrangian tracer transport

• CLUBB updated from v1 to v2

• a new convective trigger (dCAPE/ULL) based on the dynamic Convective Available Potential Energy (CAPE) (dCAPE) and the Unrestricted Launch Level (ULL) concepts is used in ZM

• minimum cloud droplet number changed

• gravity wave drag energy conservation fixed and new tunings used

• dust emission size distribution changed to emit more coarse dust particles

ELM

The land component is still ELM. Major changes since version 1 include: …

General MPAS improvements

MPAS still provides the components for ocean, sea-ice and land-ice.

• Stand-alone testing suites are available in a new version of COMPASS (https://github.com/MPAS-Dev/compass ) using standardized python libraries and numerous new test cases. 

• Automated and improved generation of variable-resolution unstructured meshes and coastlines using jigsaw (https://github.com/dengwirda/jigsaw ) and COMPASS.

• Transplanting MPAS code from the MPAS-Dev repository directly into the E3SM repository to simplify alterations, testing, and pull requests.

MPAS-Ocean

• Redi isopycnal mixing has been updated, tested, and tuned in combination with the Gent-McWilliams parameterization.

• A new semi-implicit barotropic solver has been introduced as an option.

• There have been a number of performance improvements, including an initial GPU port of several portions of the model using OpenACC directives.

• Ability to have inactive top cells below ice shelves.

• Tracking and verification of flux budgets with coupler

• Improvements in code simplicity and readability include direct access to mesh and config variables, and excluding init mode in forward runs.

• Addition of tidal forcing, wetting and drying for shorelines, internal wave drag, GOTM vertical mixing library, and sediment transport (all not yet fully validated).

MPAS-Seaice

The sea-ice component remains MPAS-seaice. Major changes since version 1 include: A new heat- and freshwater-conserving coupling of frazil ice, turning off of SSH filtering, addition of SNICAR-AD and snow grain aging.

MPAS-Albany-landice

The land-ice component remains MPAS-Albany-landice and is a static ice sheet. Major changes since version 1 include preparation for using an active ice sheet such as:

• MALI code was moved from a submodule to instead exist directly within the E3SM repository.

• An ice shelf damage evolution scheme was added, but is not yet coupled to calving or advection.

• A von Mises tensile stress calving schemes was implemented and the calving algorithm was rewritten to eliminate a number of bugs.

• The grounded marine terminus ocean melting scheme from ISMIP6-Greenland was implemented.

• The option to use a regularized Coulomb basal friction law and a general power law basal friction law were added.

• The sub-ice-shelf melting scheme from ISMIP6-Antarctica was added.

• The prescribed mask-calving forcing scheme from ISMIP6-Antarctica was added.

Coupler/Configurations

All components allow regional refinement of their meshes and an example of refinement in and around North America is provided.