Abstract
The variances of vertical velocity, w, temperature, θ, and humidity, q, that were observed in the atmospheric surface layer over a flat pine forest with an aircraft were analyzed on the basis of Monin-Obukhov similarity (MOS). The values of σw and σθ were found to obey closely the one-third power law, representing the asymptotic form of MOS under strongly unstable conditions, whereas σq was observed to display considerable scatter. This scatter can be attributed, in part, to the surface inhomogeneity, which resulted from the characteristics of the terrain, consisting of a mixture of forest stands and clearings. It was also shown that this surface inhomogeneity caused a breakdown of the similarity between scalars. On the basis of the one-third power law, three types of the variance method were applied to these variances in order to estimate surface fluxes. Comparison with the aircraft-measured surface fluxes indicated that some of the variance methods generate reasonable estimates of the sensible heat flux. For latent heat flux, the variance method could produce surface flux values comparable to the measurements, albeit with scatter, only when the constants involved were locally calibrated.
