First release of version 2.0 of the Energy Exascale Earthy System Model contains the following changes from v1.0
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
The land component is still ELM. Major changes since version 1 include: …
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.
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).
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.
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.
All components allow regional refinement of their meshes and an example of refinement in and around North America is provided.