  Anisotropy and multifractality in velocity and temperature time series
sampled at multiple heights in the roughness sublayer (RSL) over a boreal
mixed-coniferous forest are reported. In particular, a turbulent-stress
invariant analysis along with a scalewise version of it are conducted to
elucidate the nature of relaxation of large-scale anisotropy to quasi-isotropic
states at small scales. As the return to isotropy is linked to nonlinear
interactions and correlations between different fluctuating velocity components
across scales, we study the velocity and temperature time series by using
multifractal detrended fluctuation analysis and multiscale multifractal
analysis to assess the effects of thermal stratification and surface roughness
on turbulence in the RSL. The findings are compared so as to quantify the
anisotropy and multifractality ubiquitous to RSL turbulent flow. As we go up in
the RSL, (a) the length scale at which return to isotropy commences increases
because of the weakening of the surface effects and (b) the largest scales
become increasingly anisotropic. The anisotropy in multifractal exponents for
the velocity fluctuations is diminished when we use the
extended-self-similarity procedure to extract the multifractal-exponent ratios.
