Variations of Wind Fluctuations Observed at 10 m over Flat Terrain under Stable Atmospheric Conditions

Abstract

Turbulence data were collected with the use of a sonic anemometer from October 1988 to September 1989. The study site was situated amid flat terrain near Calgary, Alberta. The data have been analyzed with respect to wind speed and stability. Simple empirical equations have been established that relate median standard deviations of transverse, longitudinal, and vertical wind fluctuations (σv, σu, σw) to wind speed and static stability. One-to-one correlation coefficients between predicted and observed data were typically in excess o.90. Dispersion models utilize the ratios of turbulence parameters to wind speed (i.e., σv/U, σu/U, σw/U). These ratios, referred to as standard deviations of the wind angles, have been derived as functions of wind speed and potential temperature gradients. Values of the standard deviation of the transverse wind angle σ? are shown to be independent of stability. Standard deviations of the longitudinal and vertical wind angles (σφ, σ?) have the same exponential dependency on stability at moderate to high wind speeds. Relations between σ?, σφ, and σ? and meteorological parameters of wind speed and stability are presented in graphical form.