Turbulent Flux Measurements Above and Below the Overstory of a Boreal Aspen Forest

摘要: Turbulent flux measurements both above and beneath the canopy of a boreal aspen forest are described. Velocity skewness showed that, canopy, turbulence was dominated by intermittent, downward penetrating gusts. Eulerian horizontal length scales calculated from integration autocorrelation function or spectral peaks were 9.0 1.4 times mean height 21.5 m respectively. Above-canopy power slopes for all velocity components followed -2/3 law, whereas beneath-canopy closer to -1 short cut in vertical components. Cospectral patterns similar canopy. The Monin–Obukhov similarity wind variance well-defined atmospheric stability, Nocturnal underestimation departures this that expected theory friction velocity. Energy balance closure greater than 80% achieved at velocities 0.30 0.10 s-1, below Recalculating latent heat using various averaging periods revealed minimum 15 min required capture 90% 30-min flux. Linear detrending reduced shorter compared block averaging. Lack energy erratic behaviour led recalculation sensible fluxes ratio net radiation sum terms.