Turbulent Structure of the Marine Atmospheric Boundary Layer and Its Implications for the Inertial Dissipation Method

Sammanfattning: In order to improve climate- and weather forecasting models, a better knowledge of the physical processes taking place in the lowest part of the atmosphere over the oceans is essential. In these models it is often assumed that the atmospheric boundary layer over sea behaves in the same way as that over land. But, the results show that the processes over sea are significantly different, which has to be accounted for in the models.By using long term measurements it is shown that the surface waves play a very important role for the turbulent structure in the marine atmospheric boundary layer. For example, they give rise to a height structure that can not be found over land. A consequence of this is that measurements from a buoy (at a few meters above the surface) need to be treated different than measurements on a ship (at 10-30 m above the surface).The wave influence affects the turbulent kinetic energy budget. Besides the height dependency, the imbalance between local production and local dissipation is a function of stability, wave age and wind speed, and the commonly assumed balance can therefore be questioned. This has direct implications for the so called inertial dissipation method, a method often used to determine turbulent fluxes over sea with the aid of measurements from ships and buoys. A comparison with the more direct eddy-correlation method at 10 m height gives that the inertial dissipation method works best for near neutral conditions and growing sea.