Ground-based Doppler wind lidars are laser-based remote sensing instruments that measure wind speed and wind direction up by measuring the Doppler-shift of the backscattered laser light, typically by aerosols in the moving air.
Promising new applications of those wind lidar instruments for KNMI are real-time wind profile monitoring for operational weather forecasters and comparison with weather model data. Our R&D activities are aiming at a thorough understanding of the instruments (including their measurement characteristics and operational issues), their added value for our nationwide meteorological observation network and atmospheric research at Cabauw, and application of wind lidar data sets (measured by KNMI or third parties) for model validation.
Current wind lidar related activities within RDWD are:
(1) Two-year measurement campaign of the ZephIR 300M wind lidar at Cabauw
In the coming years ZephIR 300M wind lidars will be installed on substations within the upcoming offshore wind farms in the Dutch part of the North Sea. Their main purpose is to monitor the wind conditions at hub height. These wind lidar will provide near real-time wind profile data up to almost 300 m above sea level and will be made available as open data via KNMI.
In order to assess data availability and quality of the wind profiles under various weather conditions, KNMI has started a two-year measurement campaign of this instrument at the CESAR Observatory in Cabauw, The Netherlands , commissioned by Rijkswaterstaat. A comparison between the wind lidar and cup anemometers at several levels in the 213 meter high meteorological mast is made, while monitoring the meteorological conditions with several of in situ and remote sensing instruments.
The growing number of wind farms in the Dutch North Sea provides both the opportunity and the need to measure the wind conditions at those locations. With the increasing size of wind turbines, wind profiles up to a few hundred meters or higher, are of relevance. Wind lidars are well suitable for measuring in this range. The data can be used for nowcasting and improve weather forecasting, as well as for wind climatology purposes. Within this project KNMI gains experience with operational use of wind lidars, onshore and offshore, which is interesting for future directions in our meteorological observation network.
(2) DOWA validation
Wind lidar data sets are used to validate the upcoming Dutch Offshore Wind Atlas (DOWA) wind climatology (2008-2017), a project executed by ECN part of TNO, Whiffle and KNMI. This includes measurements from North Sea platforms (such as Meetmast Ijmuiden, Europlatform, Lichteiland Goeree, K13, data provided by ECN part of TNO) and coastal locations (Tweede Maasvlakte, by Ventolines and Rijkswaterstaat; Stellendam). The data sets used for this study consist of wind profiles up to 300m altitude for periods up to a few years and are therefore very useful to validate new (re-analysis) models.
Within the wind energy industry, wind lidar measurement campaigns have become a standard tool for wind resource assessment, resulting in data sets from different locations in the Netherlands, both onshore and offshore. When made available to KNMI, these can be used for model validation or intercomparisons with other sources of wind information. However, thorough understanding of wind lidar measurements remains crucial in proper usage of the data.
(3) Ruisdael Observatory
Within the NWO funded Ruisdael Observatory project (2018-2027) two wind lidars will be purchased, to be installed and operated at Cabauw. Their purpose will be to measure aerosols, clouds, horizontal wind, and vertical wind and turbulence, supporting the atmospheric research carried out within the Ruisdael Observatory.