Observations and parametrization of momentum transfer in heterogeneous terrain consisting of regularly spaced obstacles |
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Authors: | W P Hopwood |
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Institution: | (1) Meteorological Office, London Road, RG12 2SZ Bracknell, UK |
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Abstract: | Tethered balloon data collected over a heterogeneous, semi-rural area of southern England are presented. The terrain within
which the observations were taken is dominated by regularly spaced bluff obstacles that form the boundaries to grass fields.
The data are compared with previous surface data to assess how representative these fixed-point measurements are of area-averaged
values. It is found that there is a vertical height above which the flow approximates to being homogeneous and observations
made above it are representative of the area average. The effective roughness length for momentum is then compared with that
derived from a model describing the drag partition around isolated obstacles that are either non-porous or porous to the incident
flow. It is shown that the method chosen to partition the drag is of the right order to produce reasonable predictions of
the effective roughness length for different roughness densities. |
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Keywords: | |
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