Inter-calibration of SAR data series for offshore wind resource assessment

Merete Badger*, Tobias Torben Ahsbahs, Petr Maule, Ioanna Karagali

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

Wind observations in the marine environment are both costly and sparse. This makes wind retrievals from satellite Synthetic Aperture Radar (SAR) an attractive option in connection with planning of offshore wind farms. Because the wind power density is proportional to the wind speed cubed, it is important to achieve the highest possible absolute accuracy on SAR wind speed retrievals for wind energy applications. A method is presented for inter-calibration of SAR observations from Envisat and Sentinel-1A/B. Sensor-specific effects on the SAR-retrieved wind speeds are first quantified through comparisons against collocated ocean buoy observations. Based on global circulation model simulations of wind speed and direction, we retrieve the Normalized Radar Cross Section (NRCS) for different radar incidence angles. Residuals between the retrieved and the observed NRCS are used to inter-calibrate the observed NRCS before reprocessing to SAR wind fields. The inter-calibration leads to an improved agreement between SAR and buoy wind speeds with biases below 0.2 m s− 1 for all investigated SAR sensors. Estimates of the wind resource improve with respect to the buoy observations for ten of the twelve sites investigated. The average deviation between wind power densities is reduced from 20% to 8% as the SAR inter-calibration leads to more conservative estimates of the wind resource.
Original languageEnglish
Article number111316
JournalRemote Sensing of Environment
Volume232
Number of pages13
ISSN0034-4257
DOIs
Publication statusPublished - 2019

Keywords

  • Envisat
  • Inter-calibration
  • Offshore wind energy
  • Resource
  • Sentinel-1
  • Synthetic Aperture Radar

Cite this

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title = "Inter-calibration of SAR data series for offshore wind resource assessment",
abstract = "Wind observations in the marine environment are both costly and sparse. This makes wind retrievals from satellite Synthetic Aperture Radar (SAR) an attractive option in connection with planning of offshore wind farms. Because the wind power density is proportional to the wind speed cubed, it is important to achieve the highest possible absolute accuracy on SAR wind speed retrievals for wind energy applications. A method is presented for inter-calibration of SAR observations from Envisat and Sentinel-1A/B. Sensor-specific effects on the SAR-retrieved wind speeds are first quantified through comparisons against collocated ocean buoy observations. Based on global circulation model simulations of wind speed and direction, we retrieve the Normalized Radar Cross Section (NRCS) for different radar incidence angles. Residuals between the retrieved and the observed NRCS are used to inter-calibrate the observed NRCS before reprocessing to SAR wind fields. The inter-calibration leads to an improved agreement between SAR and buoy wind speeds with biases below 0.2 m s− 1 for all investigated SAR sensors. Estimates of the wind resource improve with respect to the buoy observations for ten of the twelve sites investigated. The average deviation between wind power densities is reduced from 20{\%} to 8{\%} as the SAR inter-calibration leads to more conservative estimates of the wind resource.",
keywords = "Envisat, Inter-calibration, Offshore wind energy, Resource, Sentinel-1, Synthetic Aperture Radar",
author = "Merete Badger and Ahsbahs, {Tobias Torben} and Petr Maule and Ioanna Karagali",
year = "2019",
doi = "10.1016/j.rse.2019.111316",
language = "English",
volume = "232",
journal = "Remote Sensing of Environment",
issn = "0034-4257",
publisher = "Elsevier",

}

Inter-calibration of SAR data series for offshore wind resource assessment. / Badger, Merete; Ahsbahs, Tobias Torben; Maule, Petr; Karagali, Ioanna.

In: Remote Sensing of Environment, Vol. 232, 111316, 2019.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Inter-calibration of SAR data series for offshore wind resource assessment

AU - Badger, Merete

AU - Ahsbahs, Tobias Torben

AU - Maule, Petr

AU - Karagali, Ioanna

PY - 2019

Y1 - 2019

N2 - Wind observations in the marine environment are both costly and sparse. This makes wind retrievals from satellite Synthetic Aperture Radar (SAR) an attractive option in connection with planning of offshore wind farms. Because the wind power density is proportional to the wind speed cubed, it is important to achieve the highest possible absolute accuracy on SAR wind speed retrievals for wind energy applications. A method is presented for inter-calibration of SAR observations from Envisat and Sentinel-1A/B. Sensor-specific effects on the SAR-retrieved wind speeds are first quantified through comparisons against collocated ocean buoy observations. Based on global circulation model simulations of wind speed and direction, we retrieve the Normalized Radar Cross Section (NRCS) for different radar incidence angles. Residuals between the retrieved and the observed NRCS are used to inter-calibrate the observed NRCS before reprocessing to SAR wind fields. The inter-calibration leads to an improved agreement between SAR and buoy wind speeds with biases below 0.2 m s− 1 for all investigated SAR sensors. Estimates of the wind resource improve with respect to the buoy observations for ten of the twelve sites investigated. The average deviation between wind power densities is reduced from 20% to 8% as the SAR inter-calibration leads to more conservative estimates of the wind resource.

AB - Wind observations in the marine environment are both costly and sparse. This makes wind retrievals from satellite Synthetic Aperture Radar (SAR) an attractive option in connection with planning of offshore wind farms. Because the wind power density is proportional to the wind speed cubed, it is important to achieve the highest possible absolute accuracy on SAR wind speed retrievals for wind energy applications. A method is presented for inter-calibration of SAR observations from Envisat and Sentinel-1A/B. Sensor-specific effects on the SAR-retrieved wind speeds are first quantified through comparisons against collocated ocean buoy observations. Based on global circulation model simulations of wind speed and direction, we retrieve the Normalized Radar Cross Section (NRCS) for different radar incidence angles. Residuals between the retrieved and the observed NRCS are used to inter-calibrate the observed NRCS before reprocessing to SAR wind fields. The inter-calibration leads to an improved agreement between SAR and buoy wind speeds with biases below 0.2 m s− 1 for all investigated SAR sensors. Estimates of the wind resource improve with respect to the buoy observations for ten of the twelve sites investigated. The average deviation between wind power densities is reduced from 20% to 8% as the SAR inter-calibration leads to more conservative estimates of the wind resource.

KW - Envisat

KW - Inter-calibration

KW - Offshore wind energy

KW - Resource

KW - Sentinel-1

KW - Synthetic Aperture Radar

U2 - 10.1016/j.rse.2019.111316

DO - 10.1016/j.rse.2019.111316

M3 - Journal article

VL - 232

JO - Remote Sensing of Environment

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SN - 0034-4257

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ER -