Field observations of coupled wind-wave dynamics using PIV

The transfers of momentum and scalars across the air-sea interface are influenced by small-scale turbulent processes. In spite of extensive existing work on the topic, our understanding of near-surface physics remains incomplete. This is partly due to the technical challenges involved in the measurement of the small-scale dynamics very close to the rapidly moving ocean surface.

We present in situ measurements of submillimeter-scale motions in the airflow above, and in the water below the wavy air-water interface. A high resolution, large field of view Particle Image Velocimetry (PIV) system was developed for measurements at the ocean surface, capable of capturing 2D velocity fields in the turbulent airflow directly above and below the wavy surface. The system was recently deployed on a single pile platform in the Szczecin Lagoon (Baltic Sea coast, Germany). We will show some preliminary results and will discuss the influence of waves on the partitioning of momentum flux within the coupled air-water wave boundary layers.