MPAS Version 8.3.0

This release of MPAS introduces new capabilities and improvements in the
MPAS-Atmosphere model and its supporting software infrastructure. Notable
changes are listed below.

Initialization:

• Addition of support for 30" BNU soil category dataset. The 30" BNU soil
  category dataset can be selected by setting the new namelist option
  config_soilcat_data to 'BNU' in the &data_sources namelist group. Use of this
  dataset requires a separate static dataset download. (PR #1322)

• Addition of support for 15" MODIS land use dataset. The 15" MODIS land use
  dataset may be selected by setting the existing namelist option
  config_landuse_data to 'MODIFIED_IGBP_MODIS_NOAH_15s' in the &data_sources
  namelist group. Use of this dataset requires a separate static dataset
  download. (PR #1322)

• Introduction of a new namelist option, config_lu_supersample_factor, to
  control the super-sampling of land use data, which may now be on either a 30"
  or a 15" grid, depending on the choice of dataset. The existing namelist
  option config_30s_supersample_factor now controls the super-sampling for 30"
  terrain, soil category, and MODIS FPAR monthly vegetation fraction data only.
  (PR #1322)

• A change in the horizontal interpolation from a four-point bilinear
  interpolation to a sixteen-point overlapping parabolic interpolation for both
  initial conditions and lateral boundary conditions. (PR #1303)

• Ability to use ICON soil moisture and soil temperature fields. (PR #1298)

• Addition of an option to skip processing of Noah-MP-only static fields in the
  init_atmosphere core. Setting the new config_noahmp_static namelist option to
  false in the &data_sources namelist group prevents the Noah-MP static fields
  from being processed when config_static_interp = true in the
  namelist.init_atmosphere file; this also permits existing static files that
  lack the Noah-MP fields 'soilcomp', 'soilcl1', 'soilcl2', 'soilcl3', and
  'soilcl4' to be used by the init_atmosphere_model program. (PR #1239)

• Memory scaling improvements to the gravity wave drag (GWD) static field
  processing in the init_atmosphere core (when 'config_native_gwd_static =
  true') to reduce memory usage when multiple MPI ranks are used. In many
  cases, these changes eliminate the need to undersubscribe computing
  resources, which was previously required in order to work around lack of
  memory scaling in the GWD static field processing. (PR #1235)

Physics:

• Update of the RRTMG LW and SW schemes, most notably with the addition of the
  exponential and exponential_random cloud overlap assumptions. The cloud
  overlap assumption and decorrelation length are now available as namelist
  options (config_radt_cld_overlap and config_radt_cld_dcorrlen, respectively).
  (PR #1296 and PR #1297)

• The incorporation of NOAA's Unified Forecast System (UFS) Unified Gravity
  Wave Physics (UGWP) suite of physics parameterizations. This physics package
  is the "NOAA/GSL" orographic gravity wave drag (GWD) suite introduced in WRF
  Version 4.3 (activated by WRF namelist option 'gwd_opt=3'), but with the
  addition of a non-stationary GWD parameterization that represents gravity
  wave sources such as deep convection and frontal instability. The use of the
  UGWP suite requires additional static field downloads. (PR #1276)

Dynamics:

• Complete port of all routines in the dynamical core to GPUs using OpenACC
  directives, including routines used by limited-area simulations. Not included
  in this release, though, is the optimization of data movement between the CPU
  and GPU memory, and the profiling and optimization of the computational
  kernels.

• A change in the zero-gradient LBC for w to a constant value of w=0 in the
  specified zone. For limited-area configurations, the change from a
  zero-gradient boundary condition for the vertical velocity, w, to a setting
  of the vertical velocity to zero in the specified region alleviates spurious
  streamers and instabilities that appeared near the boundaries in regions of
  strong inflow. (PR #1304)

Infrastructure:

• Implementation of a new capability to automatically generate package logic
  code, which determines when a package is active. This package logic is
  generated by the registry at build time through the use of a new XML
  attribute, active_when, for elements. (PR #1321)

Other:

• Addition of a new Python script for setting up MPAS-Atmosphere run
  directories. (PR #1326)

• Addition of 3-d 10 cm radar reflectivity (refl10cm) to the 'da_state' stream,
  useful for radar DA and radar obs comparison purposes. (PR #1323)

Acknowledgements: Thanks to Max H. Balsmeier (@MHBalsmeier),
Michael Barlage (@barlage), Tanya Smirnova (@tanyasmirnova), and
Michael Toy (@mdtoyNOAA) for their contributions to this release.