Langmuir circulation complex feature of the surface boundary layer of lakes [5]. It is usually produced during the stratified season by the dispersion of wave energy that can lead to sporadic turbulence in the epilimnion. Langmuir cells occur under certain circumstances when the turbulent transport creates motions that can be organized into vertical helical currents in the epilimnion and oriented in the wind direction [5, 9]. A series of clockwise and counterclockwise rotations results in linear convergence and divergence of water which cause streaks of particles at the surface of the water body (see figure) [18]. These vortices are slightly asymmetric with higher downwelling than upwelling velocities [13]. Langmuir circulation can occur with winds speeds between 2-7 m/s. At these high wind speeds the surface turbulence strong enough to form particle streaks [9]. Cells also propagate downwind with horizontal velocities comparable to the downwelling velocities [5]. In the presence of Langmuir circulation, wind energy is not only converted into a helical structured circulation, but also can lead to waves, and shear flow. Their energy, however, is often not high enough to break through the high density gradients of the thermocline. Therefore, this type of process is confined to the epilimnion [5, 9].
Fig. Langmuir Circulation