Abstract
Vertical wind speeds in an 11 m high Sitka spruce (Picea sitchensis (Bong.) Carr.) canopy in SW Scotland were measured using two Gill anemometers mounted at heights of 5.9 and 8.65 m. Small scale air movements of a type predicted by K-theory were occasionally interrupted by a downdraught of about 7 s duration and with a maximum velocity of up to 4 m sā1. In many cases the downdraught was followed almost immediately by a less intense updraught of similar duration, suggesting the passage of a large scale (> 70 m) eddy. Auto-correlation and cross correlation of the upper and lower wind speeds revealed a 20 ā 40 second periodicity in the recurrence of the gusts. Transfer function modelling found the vertical wind speed to be attenuated by about half between the upper and lower anemometers, suggesting a diversion of air flow horizontally into the trunk space. Vortex shedding from topographic features, or the intrusion of eddies from upper levels of the boundary layer were suggested as possible sources of the gusts.
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Ā© 1985 D. Reidel Publishing Company
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Crowther, J.M., Hutchings, N.J. (1985). Correlated Vertical Wind Speeds in a Spruce Canopy. In: Hutchison, B.A., Hicks, B.B. (eds) The Forest-Atmosphere Interaction. Springer, Dordrecht. https://doi.org/10.1007/978-94-009-5305-5_32
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DOI: https://doi.org/10.1007/978-94-009-5305-5_32
Publisher Name: Springer, Dordrecht
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