CCSM ESMF Implementation and Evaluation Project

Name: Stage 2 ESMF Evaluation for CCSM

Mission Statement:

To perform a Stage 2 evaluation of the use of ESMF in CCSM by implementing a sequential single executable using CAM, CLM, POP and CICE gridded components. If Stage 2 evaluation is accepted, ESMF will be formally accepted for CCSM development, and Stage 3 will proceed.

Goals:

To create a flexible framework for a CCSM executable that can be run as a sequential application. This provides a framework for running the CCSM modeling system in a easier to use and easier to load-balance fashion than the current multi-executable concurrent CCSM. This project will result in the construction new ESMF application drivers that will result in either sequential execution of CAM, CLM, POP and CICE components. To accomplish this couplers in stage-1 will be extended to necessary regridding between components grids. Stage-2 will also do any of the time-averaging needed for components needed for coupling. The atm, ice, and lnd models will run at an hour coupling frequency and the ocean model will run at a daily coupling frequency.

On-Line Project Reports

• CCSM ESMF Stage II Project Page
• CCSMF ESMF Project Page

Motivation:

The long term goal of this project is the creation of a single executable SPMD implementation of the CCSM coupled model system which can run in sequential mode, eventually being expanded to be able to run in concurrent mode as well. There are numerous advantages to the creation of such a system:

• Scientific development across all model components (e.g. CAM, CLM, POP, CSIM) will occur on one model system. Currently, one version of thermodynamic CSIM is utilized for stand-alone CAM execution, whereas another version is utilized when running the CCSM model system.
• Code maintenance and testing will be greatly simplified. Currently, numerous models components are designed to be run in several modes. For example, CLM must be supported to run as an offline driver, as part of the CAM stand-alone executable and as a component of the CCSM model system. In a unified system, all model components will only be supported in one model.
• Code duplication will be greatly reduced. As an example, currently CLM maintains separate code to read in and utilize atmospheric NCEP data. Similarly, the CCSM coupled model also maintains a separate data model (latm) which reads in and uses atmospheric NCEP data. Creation of a unified coupled model will result in the removal of maintaining and testing for separate pieces of code that have the same functionality
• SPMD is a "sweet spot" for vendor tools. As a result, the creation of a SPMD coupled model will greatly simplify the process of error tracing and portability to new platforms. Performance monitoring will also be improved since performance tools are also normally designed to work with SPMD executables.

Authority:

Bill Collins

Project Lead:

Mariana Vertenstein

Scientific Lead:

None

Resources:

• Samson Cheung -- main implementer
• Erik Kluzek -- consulting
• Brian Eaton -- code review
• Brian Kauffman -- code review
• Nancy Norton -- code review
• Tony Craig -- code review