A sketch of two wind fields and related Ekman layer transports, left: with zero wind stress curl, right: with non-zero wind stress curl. The tendency of the wind field to induce rotation can be visualized by the drifting balloon (the green stippled rectangle); it does not rotate in the left diagram but rotates clockwise in the right diagram. It is seen that Ekman pumping in the ocean occurs only where rotation is present in the atmosphere. From Tomczak and Godfrey (1994).

The wind field in the example on the left has a strong convergence (all winds converge towards the line marked by the "balloon"). The associated Ekman layer transports are directed either northward or southward and do not result in convergent water flow. In contrast, the wind field in the example on the right does not produce convergences or divergences in the atmosphere; but it drives the associated Ekman layer transports towards each other, creating strong Ekman layer convergence.

© 1996 M. Tomczak

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