Diploma Thesis

Integral Turbulence Characteristics and Their Parameterisations

Christoph Thomas (06/2001-11/2001)

Support: Thomas Foken

This study presents a re-evaluation of parameterisations from literature of integral turbulence characteristics of wind velocity components and temperature in the surface layer. From this reevaluation, recommendations for practical applications are given including a newly derived scaling factor. Integral turbulence characteristics have great importance for e.g. air pollution modelling and quality assessment of turbulence data. The parameterisations were applied to turbulence data obtained during 5 individual experiments over homogeneous and slightly heterogeneous terrain, covering a latitudinal range from 52° North to 70° South. The parameterisations, investigated in this study, include expressions for locally influencing parameters such as atmospheric stability and surface properties, and nonlocal parameters such as mixing layer height and geographical latitude. For near neutral and slightly stable conditions, integral turbulence characteristics of the vertical and horizontal wind velocities were found to be dependent on the geographical latitude. They were observed to scale best with the newly derived parameter z+ .f/u*, stemming from the Rossbynumber similarity. For unstable conditions, atmospheric stability represented by the dimensionless height ζ, derived from the Monin-Obukhov theory, was found to be the most influencing parameter for integral turbulence characteristics of the wind components. The integral turbulence characteristic of the temperature was observed to scale with the atmospheric stability over the entire stability range. Hence, local and non-local parameters were observed to affect atmospheric turbulent flow quantities in the surface layer.

last modified 2007-11-19