Estimating the longitudinal wind spectrum near the ground

Abstract

Abstract A graphical procedure for estimating the spectrum of the longitudinal wind component from height, mean wind speed, roughness length, and stability data is presented, based on observed spectra at many locations. Using non‐dimensional coordinates following Monin, the amplitude of the spectrum peak in neutral stability shows no systematic variation with height, while the corresponding dimensionless frequency varies with height to the 0.75 power. At relatively high frequencies, spectra observed in unstable conditions are indistinguishable from those in neutral stratification. At lower frequencies the ratio of the spectrum in highly unstable conditions to that in the neutral case approaches 3 : 1 at low heights and decreases to less than one in stable air.