Earth System Modeling Framework: Overview, Architecture, and Features

1. ESMF Town Hall MeetingAGU Fall Meeting 2010San FranciscoGerhard Theurich, Fei Liu, Peggy Li, Cecelia DeLucaNOAA/CIRESDecember 15, 2010http://www.earthsystemmodeling.org

2. Outline • Overview and Architecture • Support and Extras • Closer Look at Features • Projects and Applications

3. Motivation In climate research and numerical weather prediction.. 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, as we shift toward the use of scalable computing architectures In software …emergence of frameworks to promote code reuse and interoperability The ESMF is a focused community effort to tame the complexity of models and the computing environment. It leverages, unifies and extends existing software frameworks, creating new opportunities for scientific contribution and collaboration.

4. Evolution Phase 1: 2002-2005 NASA’s Earth Science Technology Office ran a solicitation to develop an Earth System Modeling Framework (ESMF). A multi-agency collaboration (NASA/NSF/DOE/NOAA) won the award. The core development team was located at NCAR. A prototype ESMF software package (version 2r) demonstrated feasibility. Phase 2: 2005-2010 New sponsors included Department of Defense and NOAA. Many new applications and requirements were brought into the project, motivating a complete redesign of framework data structures (version 3r). Phase 3: 2010-2015 The core development team moved to NOAA/CIRES for closer alignment with federal models. Basic framework development will be complete with version 5r (ports, bugs, feature requests, user support etc. still require resources). The focus is on increasing adoption and creating a community of interoperable codes.

5. Components • ESMF is based on the idea of components – sections of code that are wrapped in standard interfaces • Components can be arranged hierarchically, helping to organize the structure of complex models • Different modeling groups may create different kinds or levels of components ESMF components in the GEOS-5 atmospheric GCM

6. Architecture • ESMF provides a superstructure for assembling geophysical components into applications. • ESMF provides an infrastructure that modelers use to • Generate and apply interpolation weights • Handle metadata, time management, data I/O and communications, and other functions • Access third party libraries Components Layer Gridded Components Coupler Components ESMF Superstructure User Code Model Layer ESMF Infrastructure Fields and Grids Layer Low Level Utilities External Libraries MPI, NetCDF, …

7. Standard Interfaces All ESMF components have the same three standard methods: Initialize Run Finalize Each standard method has the same simple interface: • Steps to adopting ESMF • Divide the application into components (without ESMF) • Copy or reference component input and output data into ESMF data structures • Register components with ESMF • Set up ESMF couplers for data exchange call ESMF_GridCompRun (myComp, importState, exportState, clock, …) Where: myComp points to the component importState is a structure containing input fields exportState is a structure containing output fields clock contains timestepping information • Interfaces are wrappers and can often be set up in a non-intrusive way

8. Component Overhead • Representation of the overhead for ESMF wrapped native CCSM4 component • For this example, ESMF wrapping required NO code changes to scientific modules • No significant performance overhead (< 3% is typical) • Few code changes for codes that are modular • Platform: IBM Power 575, bluefire, at NCAR • Model: Community Climate System Model (CCSM) • Versions: CCSM_4_0_0_beta42 and ESMF_5_0_0_beta_snapshot_01 • Resolution: 1.25 degree x 0.9 degree global grid with 17 vertical levels for both the atmospheric and land model, i.e. 288x192x17 grid. The data resolution for the ocean model is 320x384x60.

9. Data Representation Options • Representation in index space (Arrays) • One or more tilesstore indices and topology • Sparse matrix multiply for remapping with user supplied interpolation weights • Highly scalable - no global informationheld locally, uses distributed directoryapproach (Devine 2002) for access torandomly distributed objects in an efficient,scalable way 2. Representation in physical space (Fields) • Built on Arrays + some form of Grid • Grids may be logically rectangular, unstructured mesh, or observational • Remapping using parallel interpolation weight generation Also: ArrayBundles or FieldBundles, which group data for convenience and performance optimization Supported Array distributions

10. Metadata Handling and Usage • Documentation of codes and data is critical as Earth system models are employed for decision making! • Metadata is represented by the Attribute class as name/value pairs • Document data provenance • Automate some aspects of model execution and coupling • Standard metadata is organized by Attribute packages • Aggregate, store, output in XML and other formats • Attribute packages include the following conventions • Climate and Forecast (CF) • Select ISO standards • METAFOR Common Information Model (CIM) • These can be linked and nested

11. Building an Information andInteroperability Layer • Parallel generation and application of interpolation weights • Run-time compliance checking of metadata and time behavior • Fast parallel I/O • Redistribution and other parallel communications • Automated documentation of models and simulations (new) • Ability to run components in workflows and as web services (new) Applications of information layer Structured model information stored in ESMF wrappers Attributes: CF conventions, ISO standards, METAFOR Common Information Model Standard metadata ESMF data structures Standard data structures Component Field Grid Clock User data is referenced or copied into ESMF structures Native model data structures modules grids timekeeping fields

12. Outline • Overview and Architecture • Support and Extras • Closer Look at Features • Projects and Applications

13. Portability and Testing • ESMF is comprehensively tested and extremely portable! • Many tests and examples bundled with the software • About 4000 unit tests • An additional, automated test harness to cover the many options related to grids and distributions • Dozens of examples • Dozens of system tests • External demonstrations, showing ESMF linked to applications • Users can separately download use test cases, with more realistic problem and data sizes • Regression tests run nightly on 24+ platform/compiler combinations

14. Backwards Compatibility • Following the next public release ESMF 5r, ESMF interfaces will be backwards compatible • This will provide a solid platform for application development • Some newer interfaces will not be included, for example • Location streams • Exchange grids • Backwards compatibility will require the use of keywords (for example, rc=localrc) for optional arguments • Set up so users will know at compile time if this was not done

15. Where to Get Help Documentation and training materials • Users Guide, comprehensive Reference Manuals • Many examples and system tests • Coming with public release 5r • Updated demonstration program • New web-based, user-friendly tutorial format If you’re stuck • Write the support line, esmf_support@list.woc.noaa.gov If you’re really stuck, we can usually arrange a call!

16. Outline • Overview and Architecture • Support and Extras • Closer Look at Features • Projects and Applications

17. Coupling options in ESMF • Fortran or C components • Single executable • Multiple executable • Web service option • Top level MPMD • Coupling communications can be called either from within a coupler or directlyfrom a gridded component – useful when it is inconvenient to return from a component in order to perform a coupling operation • Recursive components for nesting higher resolution regions • Ensemble management with either concurrent or sequential execution of ensemble members

18. Grid Remapping • Fast parallel computation of interpolation weights • Weight generation is separate from weight application (sparse matrix multiply) for flexibility • Supports grids that can be represented as combinations of triangular or rectangular elements, in 2D or 3D • Bilinear, higher order finite element patch recovery (see below), or conservative interpolation options • Pole options: n-point pole, full circle average, no pole Higher order method: • Khoei S.A., Gharehbaghi A. R. The superconvergent patch recovery technique and data transfer operators in 3d plasticity problems. Finite Elements in Analysis and Design, 43(8), 2007. • Hung K.C, Gu H., Zong Z. A modified superconvergent patch recovery method and its application to large deformation problems. Finite Elements in Analysis and Design, 40(5-6), 2004.

19. Remapping Performance • All ESMF interpolation weights are generated using unstructured finite element mesh • Increases flexibility with 2D and 3D grids • Adds overhead to bilinear interpolation • Greatly improved performance over existing conservative methods ESMF parallel conservative remapping is scalable and accurate • Platform: Cray XT4, jaguar, at ORNL • Versions: ESMF_5_2_0_beta_snapshot_07 and SCRIP 1.4 • Resolution: • - fv0.47x0.63: CAM Finite Volume grid, 576x384 • - ne60np4: 0.5 degree cubed sphere grid, 180x180x6

20. Weight Generation Options • Ways to generate interpolation weights: • Online • Subroutine calls which calculate weights during run • Can get weights or feed directly into ESMF sparse matrix multiply • Offline • Application which generates a netCDF weight file from two netCDF grid files Summary of grid remapping options is posted at: http://www.earthsystemmodeling.org/esmf_releases/non_public/ESMF_5_1_0/esmf_5_1_0_regridding_status.html

21. Performance of ESMF sparse matrix multiply • Plot shows ESMF sparse multiply used in the Community Climate System Model (CCSM) for atmosphere to ocean grid remapping • Comparable performance to native code, slightly better scaling at higher processor counts • Versions: ESMF: 400rp2, CCSM: ccsm4_0_rel08 • Resolution: f05_t12 (fv 0.47x0.63 atmosphere/land, tripole 0.1 ocean or 576x384 atmosphere/land and 3600x2400 ocean)

22. Noise reduction in CCSM transport • ESMF higher order interpolation weights were used to map from a 2-degree Community Atmospheric Model (CAM) grid to an irregularly spaced POP ocean grid (384x320) • dTAUx/dy was computed using interpolated fields – this is closely related to the curl of the wind stress, which drives the upper ocean circulation • Noise is calculated as deviation of a point from the sum of itself plus four neighbors • 33% reduction in noise globally compared to original bilinear interpolation • (Image generated by NCAR CGD Oceanography section) Interpolation noise in a derivative of the zonal wind stress Interp. noise grid index in latitudinal direction Black = bilinear Red = higher-orderESMF v3.1.1 Green = higher order ESMF v4.0.0

23. Parallel I/O • I/O is increasingly a bottleneck in high resolution simulations • ESMF parallel I/O based on the PIO library developed by NCAR/DOE • Integrated so that the user only sees ESMF data types: • ESMF_ArrayRead(), ESMF_ArrayWrite() • ESMF_FieldRead(), ESMF_FieldWrite() • NetCDF and binary formats See: PIO User’s Guide, http://web.ncar.teragrid.org/~dennis/pio_doc/html/

24. Timekeeping • Clocks • startTime, stopTime, runDuration, timeStep, many other properties • Forward and reverse modes for running clocks • Alarms • Unsticky (turn themselves off afterringing) or sticky alarms • TimeInterval and Time data types withmany operators (+,-,/,==, more) Supported Calendars: • 360 day • No leap • Gregorian • Julian • Julian Day • Modified Julian Day • No calendar • custom

25. Summary of Features • Fast parallel remapping: unstructured or logically rectangular grids, 2D and 3D, using bilinear, higher order, or conservative methods, integrated (during runtime) or offline (from files) • Core methods are scalable to tens of thousands of processors • Supports hybrid (threaded/distributed) programming for optimal performance on many computer architectures • Multiple coupling and execution modes for flexibility • Time management utility with many calendars, forward/reverse time operations, alarms, and other features • Metadata utility that enables comprehensive metadata to be written out in standard formats • Runs on 24+ platform/compiler combinations, exhaustive test suite and documentation • Couples Fortran or C-based model components

26. ESMF 5r • Represents completion of basic ESMF functions • Expected early next year – alpha versions out

27. Outline • Overview and Architecture • Support and Extras • Closer Look at Features • Projects and Applications

28. GFS GFS Atm Phys GFS Atm Dynamics GFS I/O NEMS NMM-B Atm Dynamics NMM-B Atm Phys NMM History GEOS-5 Radiation GEOS-5 LW Rad GEOS-5 Solar Rad GEOS-5 Land GEOS-5 Veg Dyn GEOS-5 Catchment GEOS-5 OGCM Poseidon GEOS-5 Data Ocean GEOS-5 Salt Water GEOS-5 Ocean Biogeo ESMF Model Map 2010 Legend Ovals show ESMF components and models that are at the working prototype level orbeyond. A Common Model Architecture NOAA Department of Defense University NASA Department of Energy National Science Foundation ESMF coupling complete Component (thin lines) Model (thick lines) CCSM4/CESM POP Ocean CICE Ice CLM Land CAM Atm FIM • Increasingly, models in the U.S. follow a common architecture • Atmosphere, ocean, sea ice, land, and/or wave models are components called by a top-level driver/coupler • Components use ESMF or ESMF-like interfaces (see left) • Many major U.S. weather and climate models either follow this architecture (CCSM/CESM, COAMPS, NEMS), want to follow this architecture for future coupled systems (NOGAPS), or have a different style of driver but could provide components to this architecture (GEOS-5, FMS) HYCOM NOGAPS Strat Chem Param Chem GEOS-5 WRF GEOS-5 Atm Dynamics GOCART GEOS-5 GWD GEOS-5 FV Dycore FV Cub Sph Dycore Tracer Advection Land Info System GSI GEOS-5 Atm Physics GEOS-5 Hiistory GEOS-5 Atm Chem GEOS-5 Aeros Chem GEOS-5 Surface Even non-ESMF codes now look like ESMF … ESMF: ESMF_GridCompRun(gridcomp, importState, exportState, clock, phase, blockingFlag, rc) CESM (non-ESMF version): atm_run_mct(clock, gridcomp, importState, exportState) (argument names changed to show equivalence) GEOS-5 Topology GEOS-5 Moist Proc GEOS-5 Lake GEOS-5 Turbulence GEOS-5 Land Ice HAF GAIM MOM4 WWIII COAMPS SWAN pWASH123 ADCIRC NCOM

29. A Common Model Architecture • The U.S. Earth system modeling community is converging on a common modeling architecture • Atmosphere, ocean, sea ice, land, wave, and other models are ESMF or ESMF-like components called by a top-level driver or coupler • Some models are modularizing further with nested components A Common Model Architecture

30. Common Model Architecture inClimate Metadata CMIP5 metadata display in Earth System Grid, developed by theEarth System Curator project in collaboration with E.U. METAFOR

31. From Common Model Architecture to Interoperability • ESMF component interfaces alone do not guarantee technical interoperability – ESMF can be implemented in multiple ways • Also need: • A common physical architecture – the scope and relationships of physical components (e.g. land surface as subroutine or component?) • Metadata conventions and usage conventions (e.g. who can modify component data?) • The next steps for modeling infrastructure involve encoding these conventions in software tools and templates

32. National Unified Operational Prediction Capability • National Unified Operational Prediction Capability (NUOPC) is a consortium of operational weather prediction centers • Developing a standard implementation of ESMF across NASA, NOAA, Navy, Air Force and other modeling applications • Defining a target level of interoperability involving multiple aspects of code – EXAMPLES: Component interface. Components have a standard calling interface to facilitate generic drivers and communication protocols. Standardization does not include specification of what specific fields are actually in the import and export state. Timekeeping. Metadata and conventions for timekeeping enable modelers to understand without code inspection whether components can be coupled together. From: Final Report from the National Unified Operational Prediction Capability (NUOPC) Interim Committee on Common Model Architecture (CMA), June 18, 2009.

33. NUOPC Compliance Checker Designed as a way to encode and check conventions Can be linked in or not at run-time Presence of standard ESMF Initialize, Run, and Finalize methods and the number of phases in each Timekeeping conforms to NUOPC conventions Fields or FieldBundles (not Arrays/ArrayBundles) are passed between Components Which Fields are passed through import States and export States Required Component and Field metadata is present

34. Global Interoperability Program • New work with ESMF includes exploration of: • self-documenting, end-to-end workflows • integration and interfacing with other frameworks • increasing usability • new computing platforms and algorithms • Global Interoperability Program (sponsor NOAA) • Support for multi-agency projects that cross domain boundaries and integrate along modeling workflows • Supports ESMF (and other) development and applications • http://gip.noaa.gov ESMF-enabled CCSM workflow implemented using Kepler