Abstract
The accuracy of wind speed measurements is important in many applications. In the present work, error standard deviations of wind speed measured by satellites and National Data Buoy Center (NDBC) buoys were estimated using triple collocation. The satellites included six altimeters, three scatterometers, and four radiometers. The six altimeters were TOPEX, ERS-2, JASON-1, ENVISAT, JASON-2, and CRYOSAT-2, whilst the three scatterometers were QUIKSCAT, METOP-A, and METOP-B and the four radiometers included SSMI-F15, AMSR-2, WINDSAT, and GMI. Hence, a total of 14 platform measurements, including NDBC buoy data, were used and the error standard deviations of each estimated. It was found that altimeters have the smallest error standard deviations for wind speed measurements followed by scatterometers and then radiometers. NDBC buoys have the largest error standard deviation. Since triple collocation can simultaneously perform error estimation as well as calibration for a given reference, this method enables us to perform intercalibration between platform measurements including NDBC buoy. In addition, the calibration relations obtained from triple collocation were compared with the calibrations obtained from the widely used reduced major axis (RMA) regression approach. This method, to some extent, can accommodate measurements in which both platforms contain errors. The results showed that calibration relations obtained from RMA and triple collocation are very similar, as indicated by statistical parameters such as RMSE, correlation coefficient, scatter index, and bias.
Highlights
Global ocean wind speed data measured by a variety of different satellite platforms are readily available in the public domain
HRoawndeovmere,rraosr satarngduaerdd dbeyviaAtibondsaolflawiannddspCeehdifaroram[1149d]i,fftehreentmmeetahsuordemreenqtupilraetfsoramfsehwavethousand collocatedbalemteimneeaetssetuirmsr,eathtmerdeeeinnstctsahtetteoprorpemsreeontedtrwus,cofeorkurruorsabindugiostmtriperteleesrcuso,llatlnsod.caNtTioDhnBe.CTrehbfeuoomryees,a.sOmufroeamlslte1n3sttsupaltdaetlilfeiotsremmgseeiannsceulruraedmlelyesnixtinclude a systems, it is found that radiometers have the largest error standard deviations followed by scatterometers, with altimeters having the smallest error standard deviations
It is believed that the apparent low accuracy of the buoy is due to spatial representativeness errors
Summary
Global ocean wind speed data measured by a variety of different satellite platforms are readily available in the public domain. These include altimeters, scatterometers, radiometers, and synthetic aperture radar (SAR). The durations of these satellite measurements amount to more than 30 years. In order to improve the accuracy of the measurements, the satellite data have previously been calibrated and validated against in situ measurements by assuming that buoy measurements are the “ground truth” even though they are not free from errors [1].
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