A layer of air of order tens of meters thick adjacent to the ground where mechanical (shear) generation of turbulence exceeds buoyant generation or consumption. In this layer Monin–Obukhov similarity theory can be used to describe the logarithmic wind profile. The friction velocity u_* is nearly constant with height in the surface layer. Compare atmospheric boundary layer, radix layer, Obukhov length, aerodynamic roughness length.