Dynamics of the Surface Layer over the Ocean as Revealed from Field Measurements of the Atmospheric Pressure

In this work we analyze measurements of atmospheric pressure, wind velocity, and water surface elevation acquired from the Air-Sea Interaction Tower during CBLAST. We review several air flow regimes. Remarkably, the data show a distinctly different behavior of the fluctuations of wind velocity and the atmospheric pressure. While the velocity field is random and exhibits the general characteristics inherent to velocity in turbulent flows, the pressure field appears highly organized and strongly correlated with the motion of the water surface. Our analysis concludes that the different rates of turbulent decay of pressure and velocity variances are leading to the observed contrast. The fact that the pressure field is dominated by the wave modulation rather than by turbulence explains why the wind-wave coupling is occuring through an instability mechanism rather than a Langevin-force (random walk) type interaction. We also discuss how the observed structure of the pressure field affects the turbulent kinetic energy ballance of the atmospheric surface layer.