A physical Earth system model typically consists of several model components, which are coupled through exchange of data[1]. For example, the well-publicized El Nino-Southern Oscillation (ENSO) phenomenon is the outcome of atmosphere-ocean interaction. Most models solve partial differential equations on a large gridpoint set for a long time period and consequently require significant amounts of high-performance computing resources. Since Earth system model components, such as global atmospheric circulation models, also contain many physical processes such as radiation, cloud formation, precipitation, etc., considerable time and manpower are needed to develop and update a production-quality model. Currently there are still many models developed and maintained by individual organizations. A software framework to facilitate coupling models and to make modes interoperable across organizations would be a great benefit to the weather and climate community.

To achieve that goal, NASA’s ESTO/CT project has funded the development of the Earth System Modeling Framework (ESMF). The ESMF project enables close collaboration from major U.S. Earth system modeling organizations. The ESMF software will consist of a superstructure for coupling and exchanging data between component models (e.g., atmosphere, ocean) and model subcomponents (e.g., physics, dynamics); and an infrastructure consisting of (1) data structures for representing grids and fields and (2) an optimized, portable set of low-level utilities. The data constructs and low-level utilities will be used by the coupling superstructure and may also be used separately to compose scientific applications. Conceptually, an application running under ESMF may be thought of as a sandwich, with the upper and lower layers provided by the ESMF and the middle layer provided by the application developer. The ESMF superstructure sits above the components of an application, controlling inter-component data transfer and sequencing. The ESMF infrastructure lies below the components, offering integrated tools for intra-component communication, error handling, time management, profiling, and other standard modeling functions. More information on ESMF can be found at [2].

To encourage the collaboration among the laboratories of the U. S. Dept. of Energy (DOE), DOE also funded the Center for Component Technology for Terascale Simulation Software (CCTTSS) as an Integrated Software Infrastructure Center (ISIC) under the Scientific Discovery through Advanced Computing (SciDAC) program. CCTTSS is dedicated to the development of a component-based software development model suitable for the needs of high-performance scientific simulation, particularly the Common Component Architecture (CCA). The CCA Forum was organized to define a minimal set of standard interfaces that a high-performance component framework has to provide to components, and can expect from them, in order to allow disparate components to be integrated to build a running application. Such a standard will promote interoperability between components developed by different teams across different institutions. More information on CCA can be found at [3].

These two emerging component-based frameworks, ESMF and CCA, have a common goal: to promote interoperability between components developed by different organizations. However, CCA provides a more generic component interface that is not specific to any one type of application while ESMF is designed with specific component interface methods that are common to Earth system model components. To investigate how an Earth system model component that is ESMF-compliant can be supported in CCA, we have designed and developed an ESMF-CCA Prototype. A simple coupled climate model is developed and used to explore the compatibility issues between ESMF and CCA. In addition, the well-known intermediate climate model for predicting ENSO events, Cane-Zebaik Model[4], is being integrated into ESMF and CCA. In this paper, we will describe ESMF, CCA, and our ESMF-CCA Prototype, discuss their relationship in the context of weather and climate modelings, and show how these frameworks can facilitate developing and coupling models. Finally, we will illustrate our ESMF-CCA Prototype with a real-time demo (see Fig. 1).

Fig. 1. Ocean model components are available to be selected during the running time of a simulation. We have developed two ocean model component with the same interface but with a different initial condition. With the ESMF-CCA Prototype, a user can dynamically select any one of several ocean model components to participate in the simulation through GUI as shown above.