3.11
Simple first-order turbulent transfer model to predict canopy momentum, heat, and moisture regimes
Michael D. Novak, University of British Columbia, Vancouver, BC, Canada
Various models of turbulence and turbulent transfer within and above canopies exist, ranging from simple first-order closure schemes up to more complex third-order closures. Recently, Pinard and Wilson (JAM 40: 1762-1768, 2001) suggested that little advantage is gained practically, if not theoretically, when applying second- and third-order closure schemes to real canopies given the uncertainties with which input parameters are known. They presented a first-order model that predicts turbulent diffusivity from turbulent kinetic energy, which is modelled from a simple but realistic budget equation, and a length scale determined from reasonable choices for "inner" and "outer" scales. However, their model is incapable of modelling counter-gradient transfers often measured in canopies associated with large scale transfers. Li et al. (BLM 33: 77-83, 1985) presented a simple first-order model that can describe counter-gradient momentum transfer but their specification of turbulent diffusivity is highly unrealistic within a canopy, their large scale transfer term is highly sensitive to input parameters, and they did not consider heat and moisture regimes. This paper presents a model that combines the best attributes of both these works and calibrates and tests it against field measurements in forest canopies. .
Session 3, Canopy micrometeorology 2
Tuesday, 24 August 2004, 8:30 AM-2:30 PM
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