Local Similarity Properties of the Continuously Turbulent Stable Boundary Layer over Greenland

Abstract

The concept of local scaling has proven to be a useful tool for the description of turbulence structures in the stable boundary layer (SBL) in mid-latitudes. In the present paper, local similarity properties of the continuously turbulent SBL over the Greenland ice sheet are investigated. The observations were obtained during the aircraft-based experiment KABEG (Katabatic wind and Boundary-layer front Experiment around Greenland) under conditions of strong katabatic winds. For the first time, this dataset allows the study of the turbulence structure in the katabatic wind system over the whole boundary layer and over a horizontal scale of 80 km. Data from six flights during different synoptic conditions are summarized. In all situations, the katabatic flow was associated with a low-level jet, and maximum wind speeds exceed 20 m s−1 in several cases. The strong katabatic winds over the Greenland ice sheet represent conditions of the fully turbulent SBL under strong baroclinicity. Almost all data were collected above the surface layer and can be attributed to the regions of local scaling or z-less scaling. The local scaling concept was found to be valid also for these strong katabatic wind conditions. Profiles of scaled variances and fluxes agree with mid-latitude results, except for the total momentum flux. For the similarity functions and eddy diffusivities of the sensible heat flux, the use of the buoyancy length scale is found to be superior compared to the local Obukhov length.