The KNMI North Sea Wind (KNW) Atlas provides wind climatology for the North Sea and the Netherlands.
The KNW-atlas contains climatological and hourly undisturbed wind data (without wind turbine wake effects) based on more than 40 years (1979-2019) of re-analyses data (https://www.knmiprojects.nl/projects/knw-atlas). The wind speeds in the atlas have a climatological accuracy comparable to that of wind measurements (better than 0.3 m/s at wind turbine heights onshore and better than 0.2 m/s at wind turbine heights offshore). So if you are interested in long-term statistical values such as averages and extremes, the KNW-atlas is hard to beat. However, due to the applied method to create the KNW-atlas, the hourly correlation with measurements (e.g. daily cycle) is rather poor. Also, the KNW-atlas lacks information above 200 meter height and information that enables further downscaling with Large Eddy Simulation (LES) methods. That is why KNMI made another wind atlas: The Dutch Offshore Wind Atlas (DOWA). The DOWA is a 10 year climatology (2008-2017) with a better hourly correlation than the KNW-atlas, information up to 600 m heights and the option to downscale the information in DOWA from hourly to less than 60 seconds and from 2.5 km to less than 100 m horizontally. Also the domain is larger than that of the KNW-atlas, including the areas where the German wind farms are (being) built and planned. The DOWA-data and all information on the DOWA-project will become available on the 17th of January 2019 via the DOWA-project website: www.dutchoffshorewindatlas.nl .
The KNW-atlas data (time series and daily fields) can be downloaded for free from the KNW-website (https://www.knmiprojects.nl/projects/knw-atlas). The website also provides a user manual and all relevant scientific documentation and information tailored to the needs of the wind energy sector. The original KNW-atlas was based on 35 years (1979-2013), but as part of the DOWA-project, the KNW-atlas is being updated until at least March 2019. The KNW-data can be downloaded from: https://data.knmi.nl/datasets?q=knw (“35 years 1979-2013” or “from 2014-present” for the added years).
The KNW-atlas is based on the ERA-Interim global re-analysis (this is a 3D summary of all relevant measurements in the world which is both the best possible fit of these measurements and consistent with the laws of physics. KNMI’s operational weather forecast model HARMONIE has been used to downscale the global re-analysis from 6 hourly to hourly and from 80 to 2.5 km grid-spacing. The downscaled re-analysis was then tuned to match high-quality wind speed measurements from the Cabauw mast (http://www.cesar-observatory.nl/) by applying a wind shear correction of 15% uniformly throughout the whole dataset. The shear-corrected data have been validated against wind mast and satellite measurements.