A satellitebased highresolution offshore wind archive for mesoscale

A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas T. Ahsbahsa, M. Badgera, C. B. Hasagera, I. Karagalia, A. N. Hahmanna, T. Sileb, and J. Manna [a] Dep. Wind Energy, DTU, 4000 Roskilde, Frederiksundsvej 399, Denmark [b] Dep. Physics, University of Latvia, Zellu St. 23, LV-1002, Riga 18. 06. 2019 DTU A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 2

Outline • The NEWA project • Satellite: scatterometer and SAR • Mean winds over Europe • Case study: Crete 18. 06. 2019 DTU A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 3

New European Wind Atlas • Multiple experiments • Large meso-scale model • Wind atlas with 50 m resolution • Launch at Wind Resource Assessment Workshop next week 18. 06. 2019 DTU A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 4

NEWA offshore wind atlas Modelling - Meso-scale Satellite - Scatterometer - Synthetic Aperture Radar - Micro-scale Experiments - Lidar (onshore, offshore) - In-situ measurements 18. 06. 2019 DTU A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 5

Meso-scale run 1989 to 2018 • 30 years of mesoscale model runs • 10 sub-domains • 30 min data for long term statistics • 3 by 3 km grid http: //www. neweuropeanwindatlas. eu/ 18. 06. 2019 DTU A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 6

Sentinel-1 Satellite winds ASCAT • Wind fields offshore from satellites • Measurements of small waves on the ocean surface to infer wind Scatterometer Synthetic Aperture Radar Sensors ASCAT Envisat, Sentinel-1 A/B Period 2007 -2018 2002 -2018 Resolution 25 km 500 m Temporal Approx 2 per day Every few days Height Surface (10 m) In short: • Scatterometer: “high” temporal, low spatial resolution • SAR: low temporal, high spatial resolution 18. 06. 2019 DTU A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 7

Extrapolating satellite wind atlases • Satellite winds tuned to 10 m – Extrapolation needed • Long term stability correction taken into account (Badger et. al. 2016) Badger, M. , Peña. A. , Hahmann, A. N. , Mouche, A. , Hasager, C. B. (2016) Extrapolating satellite winds to turbine operating heights. Journal of Applied Meteorology and Climatology, doi: 10. 1175/JAMC-D-15 -0197. 1 18. 06. 2019 DTU A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 8

Mesoscale wind atlas offshore • Mean wind speed at 100 m from 30 years of WRF • Higher wind further offshore • Mediterranean with wind features driven by local winds (e. g. Mistral, Etesian) 18. 06. 2019 DTU A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 9

Wind atlas from scatterometer • Coverage and mean wind speed at 100 m • Similar features to WRF • Artefacts from ships and islands visible 18. 06. 2019 DTU A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 10

Mesoscale and scatterometer WRF 18. 06. 2019 DTU SCAT A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 11

Wind atlas from SAR • Coverage and mean wind speed at 100 m from SAR • Offset to higher winds compared to scatterometer – Can be corrected (work in progress) • Features from the image acquisition 18. 06. 2019 DTU A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 12

Mesoscale and SAR WRF 18. 06. 2019 DTU SAR A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 13

Case study: Western Crete Example to used SAR and model data to investigate coastal offshore flows • Crete – mountainous – complex flows • Use WRF and collocated SAR images – Comparisons at 10 m – SAR images are required to cover the entire domain – 549 coinciding cases Mean wind speed from ERA 5 around Crete SAR wind fields available at: https: //satwinds. windenergy. dtu. dk/ 18. 06. 2019 DTU A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 14

Mean wind speed at 10 m (N=549) WRF 18. 06. 2019 DTU SAR A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 15

Selecting scenes by wind direction • Wind direction from ERA 5 – “upstream” of the island – Low variation – Minimum of 3 m/s “inflow” wind speed • Northerly (330° to 30°) 59 cases • Westerly (240° to 300°) 57 cases Mean wind speed from ERA 5 around Crete 18. 06. 2019 DTU A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 16

Snapshot wind comparison Northerly wind WRF 18. 06. 2019 DTU SAR A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 17

Mean wind speed for Northerly direction (N=59) WRF 18. 06. 2019 DTU SAR A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 18

Snapshot wind comparison Westerly wind WRF 18. 06. 2019 DTU SAR A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 19

Mean wind speed for Westerly direction (N=57) WRF 18. 06. 2019 DTU SAR A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 20

Summary • Two satellite and one meso-scale model offshore wind atlas created • Similar wind features on the large scale – Offset from SAR towards higher wind speeds Case study for Crete • Pronounced wind features caused by the topography of the island • Atmospheric waves are more pronounced in SAR • Conditional averaging for WRF/SAR: – Shows differences for certain wind direction regimes – Large SAR archives and long mesoscale model run make this possible Publication coming soon to WESD: “Europe’s offshore wind resource assessed from SAR, ASCAT and WRF” 18. 06. 2019 DTU A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 21

Wind direction choice 18. 06. 2019 DTU A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 22

18. 06. 2019 DTU A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 23

18. 06. 2019 DTU A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 24

Correction for SAR: comparison with ASCAT • Consistent wind direction input for SAR (ERA 5) mean=0. 68 std=0. 38 mean=-0. 08 std=0. 32 • Intercalibration of different SAR sensors • Comparison of mean wind speeds between SAR and ASCAT 18. 06. 2019 DTU A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 25

And now a map of this difference 18. 06. 2019 DTU A satellite-based high-resolution offshore wind archive for mesoscale comparison for the New European Wind Atlas 26