In the atmosphere, the transition stratum between the surface boundary layer and the free atmosphere. Ekman layer rectification describes the way the Ekman layer velocity profile differs with variations in surface winds (McWilliams and Huckle (2006) J. Phys. Oceanog. 36, 8). The Ekman spiral describes how the horizontal wind sets surface waters in motion. As represented by horizontal vectors, the speed and direction of water motion change with increasing depth.