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We started the process of consolidating our ROMS repositories. We have too many research git and svn repositories. In a few days, we will host the git repository on GitHub and will have several branches when cloning ROMS source code:

• master: Tagged versions and latest stable release version of ROMS
• develop: Main developing branch of ROMS. Not recommended for public consumption but passes the internal tests. It is recommended for ROMS superusers and beta testers.
• feature branches: Research and new development branches recommended to superusers and beta testers:
  • feature/kernels: Major update to ROMS numerical kernels (omega.F and step2d.F)
  • feature/seaice: Native ROMS sea-ice model refactoring and development
  • feature/wec: Wave Effects on Currents algorithms adopted from COAWST

I suggest waiting until we are done with the refactoring and the regular and novice user to focus on either the master or develop branches. The restructuring facilitates the maintenance of ROMS source code, the development of new algorithms, and updating of the COAWST system.

We still recommend users to interact via ​https://www.myroms.org/forum for discussions and problems. There is plenty of information at ​https://www.myroms.org/wiki

We need to consolidate the changes to ROMS due to the refactoring and development of the sea-ice model. Originally written by Paul Budgell (2005), maintained by Kate Hedstrom, and updated by Scott Durski (Durski and Kurapov, 2019, 2020). It is primarily based on Mellor and Kantha (1989) and Parkinson and Washington (1979).

The sea-ice model has been cleaned, documented, and redesigned to facilitate adjoint-based applications in the future. It has only two state variables, Fi and Si, that can be expanded. The original code has at least 39 arrays.

! Define derived-type structure ice model state and internal arrays.
 
     TYPE T_ICE
        real(r8), pointer :: Fi(:,:,:)               ! [i,j,1:nIceF]
        real(r8), pointer :: Si(:,:,:,:)             ! [i,j,1:2,1:nIceS]
      END TYPE T_ICENgrids
      TYPE (T_ICE), allocatable :: ICE(:)            ! [Ngrids]

! Ice model state prognostic variables indices.

      integer, parameter :: nIceS = 15  ! number of ice state variables
      integer :: iSice(nIceS)           ! state I/O indices
      integer, parameter :: isAice =  1 ! ice concentration
      integer, parameter :: isHice =  2 ! ice thickness
      integer, parameter :: isHmel =  3 ! melt water thickness on ice
      integer, parameter :: isHsno =  4 ! snow thickness
      integer, parameter :: isIage =  5 ! ice age
      integer, parameter :: isISxx =  6 ! internal ice xx-stress
      integer, parameter :: isISxy =  7 ! internal ice xy-stress
      integer, parameter :: isISyy =  8 ! internal ice yy-stress
      integer, parameter :: isTice =  9 ! ice interior temperature
      integer, parameter :: isUice = 10 ! ice U-velocity
      integer, parameter :: isVice = 11 ! ice V-velocity
      integer, parameter :: isEnth = 12 ! ice/brine enthalpy
      integer, parameter :: isHage = 13 ! thickness linked with ice age
      integer, parameter :: isUevp = 14 ! EVP ice U-velocity
      integer, parameter :: isVevp = 15 ! EVP ice V-velocity

! Ice model internal variables indices.

      integer, parameter :: nIceF = 24  ! number of ice field variables
      integer :: iFice(nIceF)           ! internal fields I/O indices
      integer, parameter :: icAIus =  1 ! surface Air-Ice U-stress
      integer, parameter :: icAIvs =  2 ! surface Air-Ice V-stress
      integer, parameter :: icBvis =  3 ! ice bulk viscosity
      integer, parameter :: icHsse =  4 ! sea surface elevation
      integer, parameter :: icIOfv =  5 ! Ice-Ocean friction velocity
      integer, parameter :: icIOmf =  6 ! Ice-Ocean mass flux
      integer, parameter :: icIOmt =  7 ! Ice-Ocean momentum transfer
      integer, parameter :: icIOvs =  8 ! Ice-Ocean velocity shear
      integer, parameter :: icIsst =  9 ! ice/snow surface temperature
      integer, parameter :: icPgrd = 10 ! gridded ice strength
      integer, parameter :: icPice = 11 ! ice pressure or strength
      integer, parameter :: icQcon = 12 ! ice/snow heat conductivity
      integer, parameter :: icQrhs = 13 ! RHS heat flux over ice/snow
      integer, parameter :: icSvis = 14 ! ice shear viscosity
      integer, parameter :: icS0mk = 15 ! molecular sublayer salinity
      integer, parameter :: icT0mk = 16 ! molecular sublayer temperature
      integer, parameter :: icUavg = 17 ! average mixed-layer U-velocity
      integer, parameter :: icVavg = 18 ! average mixed-layer V-velocity
      integer, parameter :: icWdiv = 19 ! ice divergence rate
      integer, parameter :: icW_ai = 20 ! melt/freeze rate at Air/Ice
      integer, parameter :: icW_ao = 21 ! melt/freeze rate at Air/Ocean
      integer, parameter :: icW_fr = 22 ! ice accretion rate by frazil
      integer, parameter :: icW_io = 23 ! melt/freeze rate at Ice/Ocean
      integer, parameter :: icW_ro = 24 ! melt/freeze rate runoff

The sea-ice model kernel is located in the ROMS/Nonlinear/SeaIce subdirectory and will be found soon in the GitHub repository feature/seaice branch. It needs testing. We hope the beta testers with some expertise in sea-ice modeling help us with testing and further development.

The data input data management is still missing but can easily be added in get_data.F and set_data.F. It was postponed until we worked on the required atmospheric fields for coupling using the ESMF/NUOPC infrastructure.

Notice that the sub-directory SeaIce containing the sea-ice model is not released yet. I am only releasing the modifications needed in the ROMS infrastructure. Our strategy is to isolate model kernels for flexibility, as we have done with Biology, Sediment, and WEC in the Nonlinear kernel sub-directory.

The ROMS source code was consolidated due to changes for new developments:

• Major update to ROMS barotropic kernel (step2d) using the Generalized Forward-Backward 3rd-order Adams-Bashforth /4th-order Adams-Moulton (FB AB3-AM4) time stepping algorithm (Shchepetkin and McWilliams, 2005; 2009)

• Implementation of the adaptive, Courant-number-dependent implicit scheme for vertical advection (Shchepetkin, 2015), which splits omega vertical velocity into explicit (W) and implicit (Wi) components.

• Porting the Waves Effect on Currents (WEC) based on the Vortex Force formulation of Uchiyama et al. (2010) and Kumar et al. (2012) based on COAWST implementation.

The actual algorithms are not released yet. However, it will be available soon in the ROMS GitHub repository in feature/kernel and feature/wec branches.

The feature branches are intended for superusers, advanced users, and beta testers.

WARNING

• All the standard input files roms_*.in were modified to add new output fields to HISTORY, QUICKSAVE, AVERAGES, and DIAGNOTIC files.

• The varinfo.yaml metadata file was updated for the new variables.

Many thanks to Sasha Shchepetkin and John Warner for their help designing and implementing these algorithms.