Abstract
The South Atlantic trades cross the equator at the height of northern summer, recurving from south-easterly to southwesterly near 5°N, and undercut the northeast trades along an extended discontinuity. The negative surface stress curl of this atmospheric current leads to upwelling and a cold ocean surface immediately south of the equator, with downwelling and higher sea temperatures to the north. This clockwise turning, cross-equatorial flow is markedly divergent between the equator and about 5°N. A band of convergence extends poleward from 5°N into the southern fringe of the northeast trades. Maximum convergence, cloudiness and precipitation frequency all occur ∼350 km south of the surface wind discontinuity and pressure minimum, in a region of high directional steadiness of wind.
