Offshore Winds - Wind Energy Meteorology: Atmospheric Physics for Wind Power Generation - page 123

Fig. 5.31 Relative frequency of relative amplitudes (percentage of mean wind speed) of 10.5 s-
gust events at 80 m at FINO1 for the year 2005. The dotted vertical lines indicate a change of bin
width (2 % in the interior part of the Figure and 30 % in the outer parts)
Fig. 5.32 Correlation
between the two Weibull
parameters A and k at each
height at FINO1, where
yellow are summer, green are
spring, red are autumn and
blue are wintertime data.
Within each seasonal result
the different measurement
heights order from upper left
(30 m) to lower right (100 m)
with 10 m increment. (From
Bilstein and Emeis 2010 )
shows data for the four different seasons and for all eight heights between 30 and
100 m with a height increment of 10 m. Please note that the upmost instrument at
100 m is on the top of the mast while all other instruments are mounted on
horizontal booms away from the mast. These lower instruments are slightly
influenced by the mast. This is why the last data point in the lower right of each
profile shown in Fig. 5.32 is a bit shifted to the right. It becomes visible that the
shape parameter decreases with the rising variability of wind speeds at higher
levels, while the scale parameter increases with height. Over the ocean, atmo-
spheric friction is not as great as over land, so the surface layer (also called Prandtl
layer) is not as thick (Türk 2008 ). For this reason, the vertical gradient of the scale