Spatio-temporal wind variability in complex terrain

Abstract

Spatial and temporal characteristics of the wind velocity in complex terrain, relevant to wind energy resources were investigated in this study. Data from one 80 m and four 50 m towers located within a range of 200 km in western Nevada, U.S., operated from August 2003 to March 2008 were used in the analysis. The average multi-annual wind speed did not show significant increase trends with increased elevation, the differences are mainly governed by the complexity of the topography including local circulations and channeling. Due to a slower increase of the standard deviation of the wind speed compared to the increase of the average wind speed, the turbulence intensity slowly decreased with an increase of the average wind speed. The wind speed was modeled using the Weibull distribution, while the wind direction was modeled using the von Mises distribution. In spite of differences in the basic wind speed statistics, the auto- and cross-correlations show a strong coherence between the wind speed and direction with slowly decreasing amplitude of the multi-day periodicity with increasing lag periods. A non-zero centerline of the diurnal component in the autocorrelation function indicated a possible long-term periodicity. Besides a pronounced diurnal periodicity at all locations, the spectral analysis showed significant annual periodicity with similar characteristics at all five locations.