Components in the Earth System Modeling Framework

1. Components in the Earth System Modeling Framework GFDL FMS Suite MITgcm NASA GSFC PSAS NCEP Forecast NSIPP Seasonal Forecast NCAR/LANL CCSM Nancy Collins, NCAR Components Workshop, Princeton, NJ

2. Outline • ESMF Component Design Principles • ESMF Component User Environments • ESMF Component Details

3. ESMF Project Overview GOAL: To increase software reuse, interoperability, ease of use and performance portability in climate, weather, and data assimilation applications PRODUCTS: • Coupling superstructure and utility infrastructure software • Synthetic code suite for validation and demonstration • Set of 15 ESMF-compliant applications (including CCSM, WRF, GFDL models; MIT, NCEP and NASA data assimilation systems) • Set of 8 interoperability experiments RESOURCES: $10.1M over 3 years from NASA Earth Science Technology Office

4. ESMF Class Structure ApplicationComponent GriddedComponent CouplerComponent Superstructure State Bundle Regrid Infrastructure Field Grid PhysGrid DistGrid F90 Data Communications Layout Array Comm Route C++ MachineModel Utilities: TimeMgr, Config, LogErr, I/O etc.

5. Design Principles:Scalable Applications Since each ESMF application is also a component, entire ESMF applications may be treated as Gridded Components and nested within larger applications. climate_comp Example: atmospheric application containing multiple coupled components within a larger climate application ocn2atm_coupler ocn_comp atm_comp phys2dyn_coupler atm_phys atm_dyn PE

6. Design Principles:Local Communication All inter-component communication within ESMF is local. climate_comp This means:Coupler Components must be defined on the union of the PEs of all the components that they couple. In this example, in order to send data from the ocean component to the atmosphere, the Coupler mediates the send. atm2ocn _coupler ocn_comp atm_comp phys2dyn_coupler atm_phys atm_dyn PE

7. Design Principles:Import/Export States Gridded Components do not have access to the internals of other Gridded Components. They have 2 options for exchanging data with other Components; the first is to receive Import and Export States as arguments. States contain flags for “is required”, “isvalid”, “is ready”, etc. coupler ocn_component subroutine ocn_run(comp, & ImportState,ExportState, Clock, rc) atm_component subroutine atm_run(comp, & ImportState,ExportState, Clock, rc)

8. Design Principles:Transforms and States Gridded Components using Transforms do not have to return control to a higher level component to send or receive State data from another component. They can receive function pointers which are methods that can be called on the states. call ESMF_CompRun(atm, xform) call ESMF_CompRun(ocn, xform) transform coupler ocn_component call ESMF_StateXform(ex_state, & xform) atm_component call ESMF_StateXform(xform, & im_state)

9. Design Principles:Registration Process Components must provide a single externally visible entry point which will register the other entry points with the Framework. Components can: - Register one or more Initialization, Run, Finalize, and Checkpoint entry points. - Register a private data block which can contain all data associated with this instantiation of the Component; particularly useful when running ensembles. Higher level Comp ESMF Framework Services cmp_final() cmp_register() cmp_run() cmp_init() Public subroutine Private subroutine

10. ESMF User Environments • Languages: F90 (predominately), C++ • Systems: Unix/Linux variants (inc IBM, SGI, Compaq, Linux clusters, Mac OS X) • Memory: MPI, PThreads/SMP • Execution: SPMD, MPMD • Runtime system: LoadLeveler, poe, bsub, mpirun

11. Component Details • Components create others • Nested parent/child relationship • Annotated States contain all data passed between components • Data objects use CF name conventions • Can be created dynamically • Initialization/Run/Finalize/Checkpoint