  We investigate experimentally the early stage of the generation of waves by a
turbulent wind at the surface of a viscous liquid. The spatio-temporal
structure of the surface deformation is analyzed by the optical method Free
Surface Synthetic Schlieren, which allows for time-resolved measurements with a
micrometric accuracy. Because of the high viscosity of the liquid, the flow
induced by the turbulent wind in the liquid remains laminar, with weak surface
drift velocity. Two regimes of deformation of the liquid-air interface are
identified. In the first regime, at low wind speed, the surface is dominated by
rapidly propagating disorganized wrinkles, elongated in the streamwise
direction, which can be interpreted as the surface response to the pressure
fluctuations advected by the turbulent airflow. The amplitude of these
deformations increases approximately linearly with wind velocity and are
essentially independent of the fetch (distance along the channel). Above a
threshold in wind speed, the perturbations organize themselves spatially into
quasi parallel waves perpendicular to the wind direction with their amplitude
increasing downstream. In this second regime, the wave amplitude increases with
wind speed but far more quickly than in the first regime.
