Preliminaries

Abstract

The atmosphere and the ocean have so many fluid-dynamical properties in common that the study of one often enriches our understanding of the other. Experience has also shown that the recognition of the underlying dynamical concepts applicable to both the atmosphere and the oceans is an excellent starting point for the study of either. Geophysical fluid dynamics is the subject whose concerns are the fundamental dynamical concepts essential to an understanding of the atmosphere and the oceans. In principle, though, geophysical fluid dynamics deals with all naturally occurring fluid motions. Such motions are present on an enormous range of spatial and temporal scales, from the ephemeral flutter of the softest breeze to the massive and persistent oceanic and atmospheric current systems. Indeed, even the “solid” earth itself undergoes a fluidlike internal circulation on time scales of millions of years, the surface expression of which is sea-floor spreading and continental drift. All these phenomena can properly be included within the domain of geophysical fluid dynamics. Partly for historical reasons, however, the subject has tended to focus on the dynamics of large-scale phenomena in the atmosphere and the oceans. It is on large scales that the common character of atmospheric and oceanic dynamics is most evident, while at the same time the majestic nature of currents like the Gulf Stream in the ocean and the atmospheric jet stream makes such a focus of attention emotionally compelling and satisfying.