The west-wind drifts on the poleward side carry back part of the water southward to reunite with the equatorial current, and thus there is set up an anticyclonic circulation of water between io and 40° in each hemisphere, the movement of the water corresponding very closely with that of the wind.
In wintertime, the cyclonic and anticyclonic areas are of increased frequency and intensity; and it is partly for this reason that many meteorologists have been disposed to regard them as chiefly driven by the irregular flow of the westerly winds, rather than as due to convectional instability, which should have a maximum effect in summer.
This produces a heaping-up of warm water towards the middle of the anticyclonic current circulation between io° and 40°, and on the other hand an updraught of deep water along the outer side of the cyclonic currents.
Two leading features, from which many others follow, are the intermediate value of the mean annual temperatures and the prevalence of westerly winds, with which drift the areas of high and low pressurecyclonic and anticyclonic areascontrolling the short-lived, non-periodic weather changes.
The cyclonic inflows and anticyclonic outflows, so characteristic of the belt of westerly winds the world over, are very irregular in the Cord illeran region; but farther eastward they are typically developed by reason of the great extent of open country.