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(a) Ascending mode (morning)
(b) Descending mode (evening)
Figure 200: Examples of the ascending, in the morning (top) and descending, in the afternoon
(bottom) swath modes of QuikSCAT on the 4th of July 2006. Images are courtesy of RSS.
(2002). The study concluded that biases were negligible for all stations and that the mission
requirements were met.
AstudyforwindresourceassessmentfromHasageretal.(2008)comparedtheRSSproduct
with in situ measurements from an offshore met. mast with standard errors ∼1.3 m s −1 for
the wind speed and ∼15 ◦ for the direction. Moreover, there was a very small difference in
their estimation of the mean wind speed and the Weibull A and k parameters from ∼3.200
QuikSCAT observations and ∼260.000 in situ measurements.
Karagalietal.(2012)usedthefullQuikSCATarchivefromRSSprocessedwiththeKu-2001
GMF, which is a descendant of the NSCAT-2 GMF, the improved version of the NSCAT-1
(GMF) (Wentz and Smith, 1999). σ0 values were mapped to a 0.25 ◦ Earth grid. This L3
product was compared with in situ derived ENW in the North Sea. Overall biases for the wind
speed were found in the order of zero (±1.2 m s −1 ), and 2.3 ◦ (±15 ◦ ) for the wind direction.
Figure 201 shows the scatterplots for the wind speed and wind direction bewteen In situ
observationsfrom4meteorologicalmastsintheNorthSeaandQuikSCAT.insituobservations
have been adjusted to ENW using the in situ wind speed and stability information. Wind
speeds lower than 3 m s −1 have been excluded due to the higher QuikSCAT uncertainties
at very low wind speeds. Note the higher scatter and the fewer observations for winds above
15 m s −1 .
For wind energy related purposes the Weibull estimates are very relevant for site identification.
Typically, 10-min in situ observations are used but at offshore locations, these are rarely
available. Karagali et al. (2012) used twice daily QuikSCAT observations for the estimation
302 DTU Wind Energy-E-Report-0029(EN)