The decomposition of 2-D velocity fields into rotational and divergent components is often used in atmospheric studies. However, its application to the ocean appears to be largely confined to the depiction by streamfunctions of the (non-divergent) vertically- integrated horizontal flow, and the mean meridional overturning flow. This paper considers the analysis of divergent oceanic flows, such as the velocity field from a single level of an ocean GCM.
A major complication to the determination of the oceanic components, compared to the atmospheric case, is the presence of land masses. But in fact, the relevant Poisson equation -the Laplacian of the unknown streamfunction equals the vorticity- is valid over the whole globe (with zero vorticity over land), provided the coastal vorticity is derived from the unknown rotational velocity field. A simple iterative method of solution based on this fact is presented. Examples of decompositions of flows from the CSIRO coupled GCM provide an interesting depiction of various gyre and overturning circulations. This decomposition is then applied to the analysis of changed ocean heat transport in a simulation of greenhouse gas-induced global warming by the GCM. The decomposition of flows in the vertical plane is also considered.
Close window or click on previous window to return to the Conference Program.
12th Conference on Atmospheric and Oceanic Fluid Dynamics