A Scientific Strategy for U.S. Participation in the GOALS (Global Ocean-Atmosphere-Land System) Component of the CLIVAR (Climate Variability and Predictability) Programme (1998)

The scientific questions, objectives, and justification for the GOALS program are discussed extensively in the U.S. GOALS Science Plan (NRC, 1995) and the CLIVAR Science Plan (WCRP, 1995). The scientific objectives of U.S. GOALS are to:

1. Understand global climate variability on seasonal-to-interannual time scales.
2. Determine the spatial and temporal extent to which this variability is predictable.
3. Develop the observational, theoretical, and computational means to predict seasonal-to-interannual variations.
4. Make experimental climate predictions on seasonal-to-interannual time scales.

5. These objectives build on the predictability that exists in the tropical Pacific Ocean associated with the coupled ocean—atmosphere processes of ENSO. Achieving them requires an enhanced understanding of seasonal-to-interannual variability in other regions. Improvements in exploiting predictability are expected as a result of developing new models that incorporate the knowledge gained from diagnostic and empirical studies in regions outside the tropical Pacific Ocean region. In particular, incremental additions to seasonal-to-interannual climate prediction skills are anticipated from the study of variations of other major tropical heat sources and sinks (e.g., the monsoon systems, the western Pacific warm pool, and the tropical American land masses) and determination of

the impacts of these variations on other regions of the tropics, subtropics, and higher latitudes. In addition, the objectives call for assessment of the predictability that may be inherent in the coupled ocean—atmosphere—land—ice system of the extratropics and incorporation of these new elements into experimental prediction schemes. The ultimate aim of GOALS is to develop an operational global climate prediction capability on seasonal-to-interannual time scales. Progress towards this aim is expected to evolve on the basis of experimental prediction experience and by concerted efforts to produce better coupled ocean—atmosphere—land models.

The underlying physical principle that guides the modeling, empirical studies, process studies, and monitoring activities of GOALS is that water, in its various forms, provides thermal inertia and heat storage anomalies in the Earth's climate system and, through hydrological processes, defines the dominant interaction between components of the climate system. In turn, water's thermal inertia, varying heat transport, and varying heat storage provide "memory" and, therefore, predictability for the climate system. Thus, GOALS focuses on the coupled ocean—atmosphere—land—ice system, with particular emphasis on the hydrological cycle, oceanic heat storage and transport variations, and land surface processes as they pertain to the prediction of seasonal-to-interannual anomalies.

Of particular interest for the U.S. program is the assessment of predictability and development of skillful prediction methods for the North American sector, while encouraging similar activities in other regions where research shows there is potential predictive skill.