The proportionality constant α in Kolmogorov theory, which states that the spectral energy S in the inertial subrange is S = αε2/3k−5/3, for ε representing the viscous dissipation rate of turbulence kinetic energy, and k the wavenumber (inversely proportional to the wavelength or eddy size). Measurements of the 1D longitudinal spectrum of the wind in the planetary boundary layer show that this constant is equal to about 0. 5.