MPAS Version 8.0.0

This major release of MPAS introduces significant new features in the
MPAS-Atmosphere model and its supporting software infrastructure.

Initialization:

• Enable parallel remapping of static fields with arbitrary graph partition
  files; special CVT partition files are no longer required.

• Reset the default for the lower air-temperature extrapolation
  (config_extrap_airtemp) from 'linear' to 'lapse-rate' in the namelist. This
  applies to initialization and to lateral boundary condition generation for
  MPAS-A.

• Set the condition for the lower extrapolation of the horizontal velocity
  such that it returns the lowest analysis level value instead of a linear
  extrapolation when the requested level is below the analysis level.

• Create a new init case (13) for creating 3-d CAM-MPAS grids.

Physics:

• Update the Noah land surface scheme to the WRF 4.5 release.

• Update the MM5 surface layer scheme to the WRF 4.5 release.

• Implemented the CCPP-compliant version of:

  • the revised MM5 surface layer scheme;
  • the parameterization of the gravity-wave drag over orography;
  • the YSU Planetary Boundary Layer scheme;
  • the scale-aware nTiedtke parameterization of convection; and
  • the WSM6 cloud microphysics parameterization.

• Correct the initialization of the maximum snow albedo over sea ice points
  (now set to 0.75 instead of 0).

• Fix the option that defines the surface albedo over sea ice points. The
  default option is now set to zero and the default value for the surface
  albedo over sea ice points is set to 0.65.

• In the dynamics, rework the computation of the advective tendency of
  potential temperature needed as forcing in the nTiedtke and Grell-Freitas
  parameterizations of deep convection. The advective tendency of potential
  temperature is now computed the same way for the nTiedtke and Grell-Freitas
  convection schemes.

  IMPORTANT NOTE: The updated Noah scheme requires new look-up tables.
  The checkout_data_files.sh script that is run at build time should correctly
  update these tables, but tables in other run directories will need to be
  manually updated.

Dynamics:

• Modify the regional MPAS-A relaxation-zone filters to increase the
  robustness of regional MPAS-A simulations, including access to specific
  relaxation-zone filter parameters through the namelist. The defaults for
  regional relaxation-zone filtering for the horizontal momentum have been
  changed from the previous release.

• Generalize the 2nd-order horizontal mixing used in the upper wave absorbing
  region in MPAS-A, including access to the configuration parameters through
  the namelist.

• The pressure-level height diagnostic is now interpolated using ln(p) for
  increased accuracy. This significantly reduces the diagnostics height bias
  in the previous version.

• Change the vertical interpolation weights for projecting cell-centered
  variables to w levels to be the vertically integrated average. Previously
  the weights represented a linear interpolation in z. These weights are
  computed in the initialization code and used in both the initialization and
  integration.

• Eliminate the need to specify a horizontal length scale in namelists
  (config_len_disp). New mesh files supply this length scale, which is read by
  the model at start-up.

• Include changes to the initialization and to MPAS-A such that this release
  can be directly used in CESM/CAM.

Infrastructure:

• Introduce a new I/O layer, the Simple MPAS I/O Layer. SMIOL provides a
  subset of the parallel I/O functionality of PIO, but with a simplified
  design that minimizes external dependencies to just the Parallel-NetCDF
  library. When the $PIO environment variable is not set at compile time,
  SMIOL will be used in MPAS.

• Refactor halo communication to make use of a new group (aggregated) halo
  exchange module. The new mpas_halo module is designed to be amenable to
  GPU-direct communication of halos with OpenACC. In this release, however,
  OpenACC directives have not yet been added.