Aircraft observations are presented of the horizontal variability in the depth of the surface evaporation duct and the relationship with the mesoscale structure of air-sea interaction processes. The 2-dimensional fields of near-surface wind, stress, wind-stress curl, air and sea-surface temperature are measured directly for flow around a headland. The sea surface temperature field indicates cold upwelling driven by the wind-stress curl. Boundary-layer stability responds rapidly to the spatial changes in surface temperature. These changes result in modification of the evaporation duct, which decreases significantly in depth over the cooler upwelling water. ¿ 2001 American Geophysical Union