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Excess resistance of bog surfaces in central Sweden

Author:
  • Meelis Mölder
  • E Kellner
Publishing year: 2002
Language: English
Pages: 23-30
Publication/Series: Agricultural and Forest Meteorology
Volume: 112
Issue: 1
Document type: Journal article
Publisher: Elsevier

Abstract english

Typical bogs in boreal forest zone can be characterized by hummock and hollow micro-topography and sparsely vegetated surfaces, thus, are quite distinct from other types of wetlands. Micrometeorological measurements were carried out in central Sweden at two bogs in different summer seasons. The data analysis aimed at obtaining good estimates for the roughness length z(ou) and the kB(-1) factor. The roughness length for wind speed (z(ou)) was estimated to be 2 cm. A good surface temperature estimate is crucial for kB-1 calculations. The surface temperature of such a heterogeneous surface showed high spatial variability, the differences between its minimum and maximum values reaching 10 K during daytime. However, an infrared thermometer averaging over a circle of a few meters still gave an acceptable result. The kB-1 factor was determined through the roughness sublayer Stanton number and the corresponding drag coefficient and was dependent on the roughness Reynolds number (Re-o). It took the form: kB(-1) = 1.58Re(o)(0.25) - 3.4. Within considerable scatter of data, a constant kB(-1) = 3.2 was also acceptable. This result lies in between the bluff-rough and vegetated surface cases.

Keywords

  • Physical Geography
  • Stanton number
  • turbulent fluxes
  • surface radiation temperature
  • roughness length

Other

Published
  • ISSN: 1873-2240
E-mail: meelis [dot] molder [at] nateko [dot] lu [dot] se

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Dept of Physical Geography and Ecosystem Science

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Researcher

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Department of Physical Geography and Ecosystem Science
Lund University
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S-223 62 Lund
Sweden

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