TURBULENCE STRUCTURE OF THE ATMOSPHERIC BOUNDARY LAYER IN STABLE CONDITIONS

Data from SABLES98 experimental campaign have been used in order to study the influence of stability (from weak to strong stratification) on the flux-profile relationships for momentum and heat: fm and fh. Standard instrumentation, 14 thermocouples and 3 sonic anemometers at three levels (5.8, 13.5 and 32 m) were available from 10 to 28 September 1998 and calculations are done in order to extract structure functions and intermittency. The results show increasing values of fm and fh with increasing stability parameter and then values remain constant. As a consequence of these constant, but different values of fm and fh for strong stability, when linear similarity functions (Businger et al., 1971) are used to calculate surface fluxes of momentum and heat an important underestimation of the turbulent mixing is produced. The differences in structure and higher order moments between stable and neutral turbulence is studied in terms of turbulent intermittent mixing and velocity PDF’s. 1