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Summary of Proposal RES3390

TitleApplication of TerraSAR-X wind retrievals for studies of wind farm wakes and coastal wind speed gradients
Investigator Ahsbahs, Tobias - Technical University of Denmark (DTU), Meteorology and Remote Sensing
Team Member
Scientist Karagali, Ioanna - Technical University of Denmark (DTU), Meteorology and Remote Sensing
Senior Scientist Badger, Merete - Technical University of Denmark (DTU), Meteorology and Remote Sensing
SummaryMeasurements of coastal offshore wind speed gradients are expensiveusing traditional in-situ measurements and data are scarce. The nearshoreregion for wind can possibly extend up to 70 km offshore [2]. Atmosphericmodelling in these regions gives poor results as soon as the wind is influencedby land or wind farm wakes [3,4]. Therefore, large scale measurements of windspeeds in the coastal zone will help to study model outputs and add an independentsource of information.The scanning radars are deployed by DONG Energy within their project“Beamed radar for Energy Assessment and site Conditions” BEACon. The experimentis located at the East Coast of England close to the wind farm WestermostRough. Scanning patterns will extend 30km offshore and cover the entire windfarm and several kilometers around it. The experiment is designed to observewakes from the turbines as well as the coastal wind speed gradient. Our projectcollaboration will focus on the SAR winds from Sentinel-1 and TerraSAR-X. Wewill use the more direct scanning radar measurements for comparisons to show howuseful SAR is to characterize coastal wind speed gradients. Wind farm wakeswill be measured uniquely detailed by the scanning radars. Comparisons with SARwind retrievals in the wake of the wind farm will add value to SAR forassessment wind farm wakes and for estimation of coastal wind speed gradients. References: [1] R. Floors, G. Lea, A. Peña, A. R. Floors, G. Lea, Report on RUNE ’ s coastal experiment and first inter-comparisons between measurementssystems E-Report DTU Wind Energy, vol. 0115. 2016. [2] R.Barthelmie, J. Badger, S. Pryor, C. B. Hasager, M. Christiansen, and B.Jørgensen, “Offshore Coastal Wind Speed gradients: issues for the design and development of large offshore windfarms,” Wind Engineering, vol.31, no. 6, pp. 369–382, 2009. [3] A. N. Hahmann, C. L.Vincent, A. Peña, J. Lange, and C. B. Hasager, “Wind climate estimationusing WRF model output: Method and model sensitivities over the sea,”International Journal of Climatology, vol. 35, no. 12, pp. 3422–3439,2015.4 [4] A. Peña and A. N. Hahmann, “Atmospheric stabilityand turbulence fluxes at Horns Rev — an intercomparison of sonic , bulkand WRF model data,” no. September 2011, pp. 717–731, 2012. Method: The obtained TerraSARX images will be processed with the APL/NOAA (Applied Physics Laboratory/National Oceanic Atmospheric Administration) SAR Wind Retrieval System (ANSWRS) software, developed at the Johns Hopkins University, to derive the wind speed, using a Geophysical Model Function (GMF) specifically developed for Xband instruments. A priori wind direction information will be derived both from in situ measurements but also from the Global Forecast System (GFS) model. Retrieved wind speeds will then be compared to the scanning radar data focusing on coastal wind speed gradients and wakes. DataRequirements: The projectrequires TerraSARX images for the area of interest from October 2016 toDecember 2017. We require as many scans as possible. Deliverables: Contributionsto conferences are expected during 2017 using preliminary results, journalpapers and a PhD thesis will be published in 2018. Funding: Fundingcomes from the Section Meteorology and Remote Sensingat the Department of WindEnergy, Danish Technical University - budget form satellite based remotesensing.

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