Near-surface turbulent temperature variances and anisotropy at multiple scales of motion

Abstract

Using multiresolution spectra data and a measure of anisotropy based on the eigen values of the Reynolds stress tensor, the scale of maximum temperature variance is found to usually be greater than the scale at which the turbulence transitions from isotropy to anisotropy. The scale of the maximum temperature variance is just as likely to be equal to the scale of maximum turbulent kinetic energy as it is to be larger or smaller. The magnitude of the maximum temperature variance is not correlated with the scale of maximum variance, but is roughly correlated with the total heat flux. Also, the magnitude of the maximum temperature variance at 5 m above the ground (agl) only roughly correlates with the magnitude at 50 m agl. The anisotropy of the turbulence at the scale of maximum temperature variance tends to be more pancake-like than cigar-like in the variances especially at 5 m agl.