A quantity with the dimensions of kinematic viscosity, defined as u_*z₀, where ''u_* is the friction velocity and z₀ the aerodynamic roughness length. In smooth flow the macroviscosity is of the order of one-tenth the kinematic viscosity. In normal atmospheric flow, which is fully rough, it is of the order of 10⁻² m²s⁻¹, or about 1000 times the kinematic viscosity. See logarithmic velocity profile.