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  • 1
    Digitale Medien
    Digitale Medien
    Energy partitioning influenced by tree spacing (1998)
    Springer
    Agroforestry systems 39 (1998), S. 211-224 
    Details
    ISSN: 1572-9680
    Schlagwort(e): Bowen ; evaporation ; Penman-Monteith ; spruce ; turbulence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract An energy partitioning experiment was set-up within an experimental agroforest site at Cloich forest, near Edinburgh. Measurements of turbulent heat fluxes were made – during non stress conditions – both directly by eddy-covariance techniques and in the case of latent heat flux indirectly through closure of the energy budget equation. These measurements were made simultaneously in the thinned plots (one plot at a time) and a reference plot to eliminate differences due to external atmospheric conditions. Observed values of Bowen ratio ranged from 1 to 3.5, with significantly lower values in the thinned plots compared with those measured in the reference plot. On separation of the Bowen ratio into its two components, it was found that sensible heat flux remained constant between plots. The latent heat flux, however, increased as the tree density was reduced. A simple model of the evaporation from the forest plots based on the Penman-Monteith equation and incorporating an under-storey component was developed and was able to accurately replicate the observed results.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005991104625
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  • 2
    Digitale Medien
    Digitale Medien
    Wind flows and forces in a model spruce forest (1994)
    Springer
    Boundary layer meteorology 69 (1994), S. 311-334 
    Details
    ISSN: 1573-1472
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Wind tunnel tests have been conducted on a 1:75 scale model of a Sitka spruce forest in a correctly scaled turbulent boundary-layer flow. 12000 tree models were manufactured with mass, flexibility and aerodynamic drag characteristics chosen to give dynamical similarity with typical 15 m trees in a 30ms−1 gale. To measure the dynamic response of a sample tree, set within this model forest, a miniature, fast response strain-gauge balance was designed and built. Linked to a computer for on-line data sampling, this balance provided measurements of the fluctuating along-wind and acrosswind components of the overturning moment at ground level, leading to values of mean and extreme moments and the frequency spectrum of the sway motion. Associated measurements of local wind flow characteristics were made with hot-wire anemometers and a laser anemometer. The response of the tree has the characteristics of classical lightly damped vibration and there is evidence that resonant sway motion increases the extreme overturning moments significantly above the values produced by wind gust forces alone.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00708860
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  • 3
    Digitale Medien
    Digitale Medien
    Wind and wind forces in a plantation spruce forest (1994)
    Springer
    Boundary layer meteorology 67 (1994), S. 161-186 
    Details
    ISSN: 1573-1472
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Observations have been made of the tubulent structure within and above a dense (LAI=10.2) plantation spruce forest along with measurements of the movement of individual trees. The mean statistics of the turbulence and the turbulence spectra are compared with observations in other crops and complementary wind-tunnel studies using 1∶75 scale plastic trees. The measurements show that momentum transport and the subsequent motion of the trees is dominated by intermittent sweep/ejection events associated with ‘honami’ waves moving across the forest. The trees themselves act as forced damped harmonic oscillators and appear to short circuit the normal turbulent energy dissipation process by efficiently absorbing energy at their resonant frequencies. It is argued that understanding the nature and formation of ‘honami’ waves over forests and crops is a crucial problem in agricultural and forest meteorology because of their important role both in turbulent transport and in causing wind damage.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00705512
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  • 4
    Digitale Medien
    Digitale Medien
    Acoustic sounder observations from an elevated location (1986)
    Springer
    Boundary layer meteorology 36 (1986), S. 307-316 
    Details
    ISSN: 1573-1472
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Details of the top of the atmospheric boundary layer obtained using an acoustic sounder at the summit of an 847 m mountain are presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00118667
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  • 5
    Digitale Medien
    Digitale Medien
    The Evolution Of Turbulence Across A Forest Edge (1997)
    Springer
    Boundary layer meteorology 84 (1997), S. 467-496 
    Details
    ISSN: 1573-1472
    Schlagwort(e): Internal boundary layers ; Forest edge ; Turbulence measurement
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract An experiment was set-up to investigate the adjustment of turbulence over a roughness transition (moorland to forest). Results from this experiment support the development of an internal boundary layer (IBL) at the transition, which propagates upwards by turbulent diffusion as a function of distance downwind from the transition. Spectra and length-scale results uphold the hypothesis that, over a transition to a rough surface, the variance distribution shifts towards smaller wavelengths/length scales. However, results suggest that the adjustment of streamwise velocity variance may be faster than the adjustment of the vertical velocity variance. The concept of an equilibrium layer developing above the new surface is supported. Fetch requirements for equilibrium are, however, found to differ between first order and second order (flux) statistics, with second order statistics requiring a longer fetch. Results indicate that fetch should exceed 25 times the height of the measurement above the zero plane, which is a 2° (±0.5) growth angle, for flux equilibrium.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1000453031036
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