Emergence of the Earth System Modeling Framework

1. Emergence of the Earth System Modeling Framework NCAR/LANL CCSM Climate GFDL FMS Suite Data Assimilation NASA GMAO Analysis NSIPP Seasonal Forecast MITgcm Weather Cecelia DeLuca Symposium on the 50th Anniversary of ONWP NCEP Forecast

2. Motivation In NWP, seasonal prediction and climate research...increased emphasis on detailed representation of individual physical processes; requires many teams of specialists to contribute components to an overall modeling system In computing technology... increase in hardware and software complexity in high-performance computing, shift toward the use of scalable computing architectures In software …development of frameworks (integrated libraries), such as the GFDL Flexible Modeling System (FMS) and Goddard Earth Modeling System (GEMS) that encourage software reuse and interoperability The ESMF is a community effort to tame the complexity of models and the computing environment. It leverages, unifies and extends existing software frameworks, breaking down institutional barriers and creating new opportunities for scientific contribution and collaboration.

3. ESMF Project Description GOALS: To increase software reuse, interoperability, ease of use and performance portability in climate, weather, and data assimilation applications PRODUCTS: • Core framework: Software for coupling geophysical components and utilities for building components • Applications: Deployment of the ESMF in 15 of the nation’s leading climate and weather models, assembly of 8 new science-motivated applications METRICS: RESOURCES and TIMELINE: $9.8M from NASA ESTO over 3 years, starting February 2002 Ongoing support from the National Science Foundation

4. ESMF Architecture • ESMF provides an environment for assembling geophysical components into applications, with support for ensembles and hierarchies. • ESMF provides a toolkit that components use to • increase interoperability • improve performance portability • abstract common services

5. Hierarchies and Ensembles ESMF encourages applications to be assembled hierarchically and intuitively Coupling interfaces are standard at each layer Components can be used in different contexts ESMF supports ensembles with multiple instances of components running sequentially (and soon, concurrently) Ensemble Forecast Seasonal Forecast assim_atm sea ice assim_atm ocean assim_atm assim_atm assim atmland atm land coupler physics dycore

6. ESMF In More Detail… • Fortran interfaces (mixed-language implementation) • Multi-platform support (SGI, Compaq, IBM, Linux - Intel, PGI, NAG, Absoft) • Clear, simple hierarchy of data objects (arrays, fields, bundles of fields, components) for developing modeling codes • Toolkits for communications (redist, halo, etc.), time management, error handling and logging, resource files, IO • Regridding library is on-line, parallelized version of SCRIP from LANL • Tools for multithreading, cache blocking, and load balancing integrated into the architecture – development has been highly performance-aware! • Data objects and toolkits have consistent naming and behavior across the framework

7. The Benefits • Standard interfaces to modeling components promote increased interoperability between centers, faster movement of modeling components from research to operations • The ability to construct models hierarchically enables developers to add new modeling components more systematically and easily, facilitates development of complex coupled systems • Multi-use objects mean that the same data structure can carry information about decomposition, communications, IO, coupling – this makes code smaller and simpler, and therefore less bug-prone and easier to maintain • Shared utilities encourage efficient code development, higher quality tools, more robust codes

8. Open Development • Open source • Currently ~800 unit tests, ~15 system tests are bundled with the ESMF distribution, can be run in non-exhaustive or exhaustive modes • Results of nightly tests on many platforms are accessible on a Test and Validation webpage • Test coverage, lines of code, requirements status are available on a Metrics webpage • Exhaustive Reference Manual, including design and implementation notes, is available on a Downloads and Documentation webpage • Development is designed to allow users clear visibility into the workings and status of the system, to allow users to perform their own diagnostics, and to encourage community ownership

9. ESMF Key Accomplishments • Public delivery of prototype ESMF v1.0 in May 2003 • Monthly ESMF internal releases with steadily increasing functionality • Completion of first 3 coupling demonstrations using ESMF in March 2004 • NCAR CAM with NCEP SSI • NCAR CAM with MITgcm ocean • GFDL B-grid atmosphere with MITgcm ocean • All codes above running as ESMF components and coupled using the framework, codes available from Applications link on website • Other codes running as ESMF components: MOM4, GEOS-5 • Less than 2% lines of source code change • On track for delivery of ESMF v2.0 on 23 June 2004 • 3rd Community Meeting to be held on 15 July 2004 at NCAR

10. Interoperability Experiments Completed 1 GFDL B-grid atmosphere coupled to MITgcm ocean Atmosphere, ocean, and coupler are set up as ESMF components Uses ESMF regridding tools 3 NCAR Community Atmospheric Model (CAM) coupled to MITgcm ocean Atmosphere, ocean, and coupler are set up as ESMF components Uses ESMF regridding tools 2 Temperature SSI import Temperature SSI export Temperature difference NCAR Community Atmospheric Model (CAM) coupled to NCEP Spectral Statistical Interpolation (SSI) System, both set up as ESMF components Experiment utilizes same observational stream used operationally at NCEP

11. Next Steps • Integration with data archives and metadata standardization efforts, anticipate collaboration with Earth System Grid (ESG) and European infrastructure project PRISM • Integration with scientific model intercomparison projects (MIPs), anticipate collaboration with the Program for Climate Model Diagnosis and Intercomparison (PCMDI), other community efforts • Integration with visualization and diagnostic tools for end-to-end modeling support, anticipate collaboration with the Earth Science Portal (ESP) • ESMF “vision” for the future articulated in multi-agency white paper on the Publications and Talks webpage

12. More Information ESMF website: http://www.esmf.ucar.edu 3rd Community Meeting on 15 July at NCAR