On the Vertical Turbulent Structure of the Marine Atmospheric Boundary Layer

The objective of this work is to study some characteristics of the vertical turbulent structure of the Marine Atmospheric Boundary Layer (MABL). Measurements were taken at Nantucket Island during July and August 2003 in the frame of the CBLAST-Low project, using both in situ, and remote instrumentation. Results regarding the MABL structure, using data from a sodar (up to 400m height) and from a sonic anemometer (at 20m height) for the 15th of August 2003, are presented. The sodar was measuring the horizontal wind speed and direction, the vertical component of the wind (w), the standard deviations of the three wind components (vertical, northeastward and northwestward), the averaged covariance moments of the wind components and the atmospheric static stability. The total vertical momentum flux, the turbulent kinetic energy (TKE), and the turbulence intensity for the three wind components were also calculated. The sonic anemometer was measuring the three components of the wind and related quantities. It was found that the atmospheric stability and the turbulence quantities (TKE, momentum fluxes and turbulence intensity ) vary with respect to the prevailing conditions i.e. the intensity and direction of the wind. More specifically, under light southerly winds the atmosphere was very stable and low values of turbulence were observed. Under moderate to strong southwesterly flow, less stable and neutral atmospheric conditions appeared and the corresponding turbulent quantities were characterized by higher values.