BOX 10.2 THE EARTH SYSTEM MODELING FRAMEWORK (ESMF): CASE STUDY
Following reports on U.S. climate modeling in 2001, federal agencies made substantial investments in software infrastructure and information systems for both modeling and analysis. ESMF is a high-profile activity that was funded in 2001 by the National Aeronautics and Space Administration (NASA), and continues to be developed and maintained under funding by the Department of Defense, NASA, the National Science Foundation (NSF), and NOAA. The first cycle of ESMF was funded as a computational technology activity focused on model coupling in both the weather and climate community. In the second cycle of ESMF, the focus was extended from technology to the formation of a multiagency organization. As discussed in Chapter 2, this focus on process and governance included development of ways to manage sponsor and user expectations, requirements, and delivery.
Building upon earlier work at GFDL and Goddard Space Flight Center (GSFC), ESMF introduced the notion of a superstructure (Collins et al., 2008; Hill et al., 2004) providing a common vocabulary for describing model components (e.g., ocean, atmosphere, or data assimilation package), with their own gridding and time-stepping algorithms, and the fields they exchange. The common vocabulary permitted components to be coupled with relatively little knowledge of the internal working of other components, other than those exposed by the interface. This approach has proved very powerful and attractive for communities whose scientific activities depend upon component-level interoperability. In particular within the numerical weather prediction (NWP) community, many participants in the National Multi-Model Ensemble are building the National Unified Operational Prediction Capability,a which utilizes ESMF as part of its foundation.
ESMF is also used within some single-institution frameworks, such as the GEOS system from NASA GSFC, and the Coupled Ocean/Atmosphere Prediction System.
NCAR and GFDL have not adopted ESMF as their central framework. GFDL already had internally developed the FMS, from which ESMF borrowed ideas. NCAR was also actively testing another framework alternative, the Model Coupling Toolkit (MCT), while ESMF was under development, and for pragmatic reasons adopted MCT for high-level coupling while using some of the lower-level functionality of ESMF. However, their own frameworks remain architecturally compatible with adoption of ESMF; and in fact ESMF is often the lingua franca, or the common language, when their components are widely used in other communities (such as GFDL’s Modular Ocean Model).
between functionally equivalent frameworks has costs, few technical barriers to doing so exist should a compelling need arise.
With ESMF and other infrastructure activities, the climate modeling community is seeing the natural evolution of infrastructure adoption. Individuals, communities, and institutions are seeing advantage. The committee believes that the community is now at the point where the benefits of moving to a common software infrastructure out-