Wind fluctuations over the North Sea

Abstract

Climatological patterns in wind speed fluctuations with periods of 1 min to 10 h are analysed using data from a meteorological mast in the Danish North Sea. Fluctuations on these time scales are of particular relevance to the effective management of the power supply from large wind farms. The Hilbert-Huang transform (HHT) is shown to be an effective tool for analysing long time series of wind speed observations, as it describes the time-evolving spectral information in the time series. By binning and averaging the time-evolving spectrum, the average spectral behaviour of the wind speed under a certain class of conditions can be found. Here, the HHT is applied to create conditional spectra which demonstrate patterns in the occurrence of severe wind variability. It is shown that wind fluctuations over the North Sea are more severe for westerly flow than for easterly flow, and that severe fluctuations are often observed in the vicinity of precipitation. The most severe wind fluctuations occur in the autumn and winter seasons, and are slightly more common when the pressure tendency is rising. Further, it is found that the wind is more variable for atmospherically unstable conditions than for stable conditions.

Automatic Classification of Offshore Wind Regimes With Weather Radar Observations

“…Statistical analysis of wind data from Horns Rev showed that this variability was actually the result of frequent and sudden changes of wind regimes (i.e., wind fluctuations with specific frequency and amplitude) over waters [5], [6]. Subsequent analysis showed that large wind fluctuations tended to be coupled with specific climatological patterns and, particularly, the occurrence of precipitation [7]. This suggests that precipitation could be used as an early indicator for high wind variability.…”

On the correlation of spatial wind speed and solar irradiance variability above the North Sea

“…Consequently the wind fluctuations are transformed to very large power fluctuations. Vincent and Hahmann (2011), Heggem et al (1998) and others showed that a typical weather situation, which enhances mesoscale wind variability, are cold air outbreaks on the rear of low pressure systems. When the cold air is advected over warm water, cellular clouds develop.…”

Spectral Properties of ENVISAT ASAR and QuikSCAT Surface Winds in the North Sea

“…The spectral properties of surface winds are fundamental for oceanic modeling and are used as a measure of accuracy for short-term forecasting in the meso-scale range [6] and for estimating extreme winds [7]. The spectral properties are also essential in order to understand the nature of spatially coherent surface winds in terms of the effective spatial resolution of different products.…”