Turbulence characteristics of the stable boundary layer over a mid-latitude glacier. Part I: A combination of katabatic and large-scale forcing

摘要: Profile and eddy-correlation (heights of 4 10 m) measurements performed on the Pasterze glacier (Austria) are used to study characteristics stable boundary layer under conditions katabatic large-scale forcing. We consider cases where forcing results in a downslope (or following) ambient wind. The analysis averaged spectra cospectra reveals low frequency perturbations that have large influence variances temperature horizontal wind components also alter momentum sensible heat flux. Only spectrum vertical speed is comparable universal spectra. occur as brief intermittent events result downward entrainment air thereby producing enhanced fluxes well upward with various magnitudes timescales. After were high pass filtered, normalised standard deviations compare favourably findings literature within range 0>z/L>0.5. For larger z/L they deviate an increased from thus non-stationarity. In line this, turbulent kinetic energy budget (at m height) indicates production (shear) balance destruction (buoyancy dissipation) 0>z/L>0.3. Non-dimensional gradients 0>z/L>0.3 slope about 3.5. scatter for dimensionless gradient quite large, gradients. z/L>0.3 imbalance grows non-dimensional considerably accepted values Average roughness lengths flux derived profiles respectively 1 × 10-3 6 10-5 m, consistent literature. ratio (z0h/z0m) compares those predicted by surface renewal models. A variation this Reynolds number not indicated our data.