Fróðskaparrit - 01.01.2007, Blaðsíða 142

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VALIDATION OF THE ECMWF ANALYSIS WAVE DATA
FOR THE AREA AROUND THE FAROE ISLANDS
1-dimensional spectrum at WVD-4 on date 9/9 time 0:48 year 2000 (ECMWF spectra at time 0:00)
1-dimensional spectrum at WVD-4 on date 25/8 time 13:18 year 2000 (ECMWF spectra at time 12:00)
Figure 7. Two recorded 1D wave spectra at WVD-4 in Event I vs. lD-wave spectra from ECMWF.
events. The measurements on the Faroe
shelf suggest a consistent positive bias in
the T wave period, but this trend is not
supported by the measurements at K7.
Clear half-daily variations occur in
wave height, direction, period and spectral
shape in the summer events. One example
of this is the period 27/8-31/8 2000 in Fig-
ures 4 and 6. Some speculations on the
causes for these variations are presented in
Niclasen and Simonsen (2005a).
The modelled 1D spectra resemble the
measured 1D spectra quite well. The EW4
spectra are smoother, in time and fre-
quency, than the observed spectra, and
double peaked spectra are much rarer in
the modelled spectra (Figure 6). Much of
this can be explained by the coarser time
and frequency resolution of the EW4
model compared to the WVD-4 buoy, but
not all. On the 25/8 2000 a clear arrival of
incoming swell is apparent in the buoy
spectra, but the corresponding feature in
the EW4 spectra is vague and diffuse (Fig-
ure 6 and lower plot in Figure 7). The ob-
served spectra have a tendency to have