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4. WRF and ESMF Convergence

4. WRF and ESMF Convergence. WRF ExOB Meeting U.S. Naval Observatory, Washington, D.C. 28 April 2006. Background of WRF-ESMF Convergence. Objective: Transition to an integrated ESMF-WRF end state. Primary goals : Minimize effort to couple WRF with other component models.

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4. WRF and ESMF Convergence

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  1. 4. WRF and ESMF Convergence WRF ExOB Meeting U.S. Naval Observatory, Washington, D.C. 28 April 2006

  2. Background of WRF-ESMF Convergence • Objective: Transition to an integrated ESMF-WRF end state. • Primary goals: • Minimize effort to couple WRF with other component models. • Maximize computational performance, versatility, interoperability • and system supportability. • Determine how best to proceed. • Technical Workshop on WRF-ESMF Convergence held in Boulder, • 9-10 February 2006. Attended by 13 experts from res. and ops. • Final report delivered 12 April 2006. • Critical requirement: • - The integrated WRF-ESMF end-state must retain a • single version-control system that preserves WRF science • codes as a community modeling system (Reference system) shared by research and operations.

  3. Principal Outcomes of WRF-ESMF Workshop - 1 • Three possible strategies for convergence of WRF and ESMF • WRF uses ESMF for high-level coupling (i.e., coupling of the • entire WRF code to other models). (Completed; see slide 5) • WRF may use ESMF low-level utilities. (near term) • - e.g., WRF now uses ESMF calendar utility; others could be possible. • WRF may use ESMF components internally. (long term) • - e.g., ESMF-compatible interfaces for physics & dynamics packages • - Dependent on requirements of WRF users and maturity of ESMF. • Code maturity • It will take 3-5 years for ESMF to mature to fully support WRF. • It will take another 3-5 years to rewrite WRF to use ESMF • infrastructure alone to reproduce WRF’s current functionality. • 3. Assessment of ESMF and WRF for grid nesting • ESMF coupling is somewhat similar to grid nesting in WRF. • ESMF is not currently optimized or designed for the precise • mass balancing required for NWP applications. 3

  4. Principal Outcomes of WRF-ESMF Workshop - 2 • 4. Complexity of software frameworks • Range of functionality of ESMF and WRF inevitably leads to greater • code complexity. Soft. Eng. best practices result in greater opacity. • WRF is a science model as well as a framework; ESMF is a technical • framework only. • Framework complexity is not an issue to some users, but may • impede progress for others using the same framework. • Streamlining the WRF framework • The complexity and layered organization of WRF are appropriate, • considering its degree of flexibility and range of functionality. • WRF registry can be simplified due to recent improved f90 compilers. • Source-translation tools can be introduced to WRF to automate • vertical index translation, leading to greater physics interoperability. • WRF build mechanism can be standardized. • Some additional code streamlining steps are possible.

  5. Current ESMF-WRF Integration: WRF as an ESMF component • The existing WRF Framework has been adapted by NCAR so it can be invoked (optionally) as an ESMF component module. Example of possible application: NCEP Hurricane WRF Target implementation: FY07 ESMF Driver: Hurr-WRF Forecast Coupler Ocean System WRF Atmos. Model Dynamics, Physics & I/O run in the WRF Infrastructure Coupler HYCOM WaveWatchIII Green: User’s model components; Tan: User-written ESMF coupler; Violet: User-written ESMF Driver

  6. Status of Key Questions from 2005 • ________________ Question___________________________________ Status__________ • 1. What is performance penalty of ESMF (as currently exists)? 0 - 5% • What is the initial resource commitment for hydrodynamic 0.5 - 1.0 Person-yrs • models to become “ESMF conformable”? • 3. Can developers remain insulated from ESMF internal codes? TBD • Can an integrated WRF-ESMF system retain or improve on TBD • essential WRF characteristics? • - version control? - supportability, maintenance? • - functional versatility? - portability, scalability? • - interoperability? - grid nesting? • Can research community accomplish its WRF goals TBD • via WRF-ESMF end state? • 6. When will missing ESMF components be available? 3-5 years • 7. How long for WRF partners to reach common end state? 5-7 years • 8. What is the end-state design? TBD

  7. Next Steps • Agency management (POCs) review and comment on • workshop report. • What is best path forward for WRF community? • Near term: - Support and use WRF as an ESMF • component for coupled model • applications. • - Explore use of additional ESMF • low-level utilities in WRF. • Long term: TBD, after more development of • and experimentation with ESMF.

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