Omega

The Ocean Model for E3SM Global Applications (Omega) initially is an eddy-resolving, global ocean model in the early stages of development by the E3SM ocean team. The first release is planned for Summer 2026. A non-eddying configuration will be released in early 2027.

The model is written in c++ using the Kokkos framework for performance portability. Omega is based on the TRSK formulation for geophysical models on unstructured meshes. The first version of Omega will primarily be a direct port of the MPAS-Ocean component of E3SM for comparison purposes.

Development is taking place at https://github.com/E3SM-Project/Omega.

User's guide

• Quick Start for Users
• CMake-based Omega Build
  • Standalone Build
  • E3SM Component Build
• Data Types and Precision
• Machine Environment (MachEnv)
• Model Configuration (Config)
• Omega Broadcast
  • Broadcasting Functions
  • Non-blocking Broadcasting Functions
• Omega Logging
  • Logging in Standalone Build mode
  • E3SM Component Build
• Driver
• Domain Decomposition (Decomp)
• Dimension
• Error handling
• Fields and Metadata (Field)
• Parallel IO (IO)
• IO Streams (IOStream)
• Halo Exchanges (Halo)
• Horizontal Mesh
• Horizontal Operators
• Auxiliary Variables
• Auxiliary State
• Tendency Terms
• Tendencies
• Ocean State
• Time Manager (TimeMgr)
• Time stepping
• Global Reductions
• Tracers
  • Updating tracer defintions in TracerDefs.inc file
  • Selecting tracers using YAML configuration file
• Tridiagonal Solvers

Developer's guide

• Quick Start for Developers
  • Getting set up
  • Building and testing Omega
  • Code development
• Development Conda Environment
  • Installing Miniforge3
  • Creating the Conda Environment
  • Updating the Conda Environment
• Linting Code
  • Enabling Lint Checks
  • Bypassing Linting
  • Linting C++ Code
  • Linting Python Code
  • Updating the linting pacakge
• Documentation
• Building the Documentation
• Data Types and Precision
• Arrays and Kokkos
• Machine Environment (MachEnv)
• Model Configuration (Config)
• Driver
  • ocnInit
  • ocnRun
  • ocnFinalize
• Omega Broadcast
  • Code Structure
  • IBroadcast Interface
  • Integration with MPI
• Omega Build with CMake
  • Step 1: Setup
  • Step 2: Update
  • Step 3: Build
  • Step 4: Output
• Developing Omega Logging
  • Initializing Omega Logger
  • Creating Logging Macros
  • Customer formatter for Kokkos
• Domain Decomposition (Decomp)
• Dimension
• Error Handler
• Fields and Metadata (Field)
• Parallel IO (IO)
• IO Streams (IOStream)
• Halo Exchanges (Halo)
• Horizontal Mesh
• Horizontal Operators
• Auxiliary Variables
  • Basic class structure
  • Configuration enums
  • Constructor
  • Compute member functions
  • Implemented groups
• Auxiliary State
  • Initialization
  • Creation of non-default auxiliary states
  • Computation of auxiliary variables
  • Removal of auxiliary states
• Tendency Terms
• Tendencies
  • Initialization
  • Creation of non-default tendencies
  • Computation of tendencies
  • Removal of tendencies
• Ocean State
• Time Manager (TimeMgr)
  • Class Descriptions
  • Implementation
• Time stepping
  • Time stepper type
  • TimeStepper base class
  • Implemented time steppers
• Global Reductions
  • Global sum
  • Global sum with product
  • Global sum multi-field
  • Global sum multi-field with product
  • Global minval and maxval
  • Utility functions globalMin globalMax
• Tracers
  • Concepts
  • Initialization and Finalization
  • Key APIs
• Tridiagonal Solvers
  • Representations of tridiagonal systems
  • Using tridiagonal solvers

Design documents

• Omega V0: Shallow Water
• Broadcast
• Config
• DataTypes
• Decomp
• Driver and Component Layer
• Equation of State
• ErrorHandler (Error)
• Halo
• Horizontal Mesh
• Logging
• MachineEnv
• Metadata
• Input/Output (IO)
• IOStreams
• Global Reductions
• State
• Tendency
• Tendencies
• Auxiliary variables
• AuxiliaryState
• TimeManager
• Timers
• Time Stepping
• Tracer Infrastructure
• Tridiagonal Solver
• Vertical Mixing Coefficients
• Template