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P. D. Jungerius 《地球表面变化过程与地形》1984,9(6):509-512
Blowouts are the main feature of wind erosion in the dunes along the Dutch coast. A number of characteristics, such as their growth against the prevailing wind and the spontaneous stabilization when certain dimensions are reached, are believed to be caused by a prominent quality of the southwest wind, viz. its gustiness. This hypothesis is tested in a two-dimensional computer model which simulates the effect of wind gusts on a sandy surface along the main axis of the blowout. A number of constraints based on field observations are built into the model. The results closely resemble the longitudinal section of the blowout. 相似文献
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We describe the results of an experiment focusing on wind speed and momentum fluxes in the atmospheric boundary layer up to
200 m. The measurements were conducted in 1996 at the Cabauw site in the Netherlands. Momentum fluxes are measured using the
K-Gill Propeller Vane. Estimates of the roughness length are derived using various techniques from the wind speed and flux
measurements, and the observed differences are explained by considering the source area of the meteorological parameters.
A clear rough-to-smooth transition is found in the wind speed profiles at Cabauw. The internal boundary layer reaches the
lowest k-vane (20 m) only in the south-west direction where the obstacle-free fetch is about 2 km. The internal boundary layer
is also reflected in the roughness lengths derived from the wind speed profiles. The lower part of the profile (< 40 m) is
not in equilibrium and no reliable roughness analysis can be given. The upper part of the profile can be linked to a large-scale
roughness length. Roughness lengths derived from the horizontal wind speed variance and gustiness have large footprints and
therefore represent a large-scale average roughness. The drag coefficient is more locally determined but still represents
a large-scale roughness length when it is measured above the local internal boundary layer. The roughness length at inhomogeneous
sites can therefore be determined best from drag coefficient measurements just above the local internal boundary layers directly,
or indirectly from horizontal wind speed variance or gustiness. In addition, the momentum and heat fluxes along the tower
are analysed and these show significant variation with height related to stability and possibly surface heterogeneity. It
appears that the dimensionless wind speed gradients scale well with local fluxes for the variety of conditions considered,
including the unstable cases. 相似文献
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