Instrumental errors in spectral-width turbulence measurements by radars

► When standard spectral width procedures are used to determine atmospheric turbulence strength, negative turbulence energy dissipation rate can result. We investigate the reasons and find variability of the mean wind causes variances in the theoretical spectral width, and these are shown to be the major cause of the negative values. Errors in determination of experimental widths are a secondary cause, and incorrect compensation for anisotropy of scatter is less important. ► Both positive and negative values of energy dissipation rate need to be included in calculations for reliable estimates of mean values-negative values cannot be ignored. ► Correct calculation of the theoretical width is important, and a new improved formula has been introduced, based on detailed model studies. ► Our results suggest that measurements with radars with one way half-power half-width of more than 3.5° are often unreliable.