Parcs

ID	TITEL	DATENTYP	AUTOR	JAHR
27622	Bibliographie NPHT	Project	Nationalparkrat Hohe Tauern	2013

Bemerkungen/Beschreibung

Boundary Layer meteorology, 87(1): p 117-145
Profile and eddy-correlation (heights of 4 and 10 m) measurements performed on the Pasterze glacier (Austria) are used to study the characteristics of the stable boundary-layer under conditions of katabatic and large-scale forcing. We considere cases where large-scale forcing results in a downslope (or following) ambient wind. The analysis of the averaged spectra and cospectra reveals low frequency perturbations that have a large influence on the variances of temperature and horizontal wind components, and also alter the cospectra of momentum and sensible heat flux. Only the spectrum of the vertical wind speed is comparable to universal spectra. The low frequency perturbations occur as brief intermittent events, and result in downward entrainment of ambient air, thereby producing enhanced downward sensible heat fluxes and downward as well as upward momentum fluxes with various magnitudes and timescales. After the variances were high pass filtered, the normalised standard deviations of wind speed and temperature compare favourably to findings in the literature within the range 0<z/L<0.5. For larger z/L they deviate as a result of the increased influence from low frequencey perturbations, and hence non-stationarity. In line with this, the turbulent kinetic energy budget (at 4 m height) indicates that production (shear) is in balance with destruction (buoyancy and dissipation) within the range 0<z/L<0.3. Nondimensional gradients of wind speed within the range 0<z/L<0.3 have a slope of about 3.5. The scatter for the dimensionless temperature gradient is quite large but the slope is comparable to that for wind speed gradients. For z/L.0.3 the imbalance in the turbulent kinetic energy budget grows and non-dimensional gradients for wind speed and temperature deviate considerably from accepted values as a result of increased non-stationarity. ...

Eintrag Nr. 13243

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