Excess resistance of bog surfaces in central Sweden

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Abstract

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.

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Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Physical Geography

Keywords

  • Stanton number, turbulent fluxes, surface radiation temperature, roughness length
Original languageEnglish
Pages (from-to)23-30
JournalAgricultural and Forest Meteorology
Volume112
Issue number1
Publication statusPublished - 2002
Publication categoryResearch
Peer-reviewedYes