Turbulence Measurements at the Sea Coast during High Winds

Abstract

Turbulent properties of longitudinal wind velocities were studied from wind records observed in 150m meteorological tower on the coast. It was recognized that the wind from the sea was inflenced by the terrain features near the tower and the magnitude of turbulent velocities increased with decreasing height. The effect of terrain roughness was found clearly on the intensity of turbulence, but was hardly noticed on the scale of turbulence. The low-frequency part of power spectrum was greatly influenced by unknown causes except terrain roughness, and a considerable discrepancy was noticed from one observation to another. It would be hard to represent whole power spectra by one simple algebraic expression. The discrepancy was less between vertical correlations than between longitudinal scales. It might be expected from vertical correlations between various heights that a vertical scale was increasing and phase of gusts was advancing with increasing height.

Stability modifications of the Frøya wind spectrum

“…Thus, very accurate temperature profile measurements are required to ensure that near-neutral data only are included in the analysis and that the spectrum can adequately be extrapolated to severe conditions. Insufficient temperature profile data were a severe shortcoming of some earlier studies (Wills et al, 1986;Shiotani, 1975;Ochi and Shin, 1988).…”

“…The low frequency range is generally associated with significant uncertainty. This is so both because most investigations (Andersen, 1991) have focused on higher frequencies reflecting the needs for most land based structures, but also because very few studies have been made over the ocean (Wills et al, 1986;Shiotani, 1975;Ochi and Shin, 1988). Also, the low frequency range is known to be very sensitive to the effects of MBL stability (Plate, 1982).…”