# The RUNE Experiment--A Database of Remote-Sensing Observations of Near-Shore Winds
## 2 Site and Instruments  
The RUNE near-shore experiment was conducted at the western coast of Denmark, as illustrated in Figure 1, on an area of about 9 km \(\times\) 5 km in the Lemvig municipality. A closer view of the area with the positions used for the installation of the lidars is shown in Figure 2.  
Figure 1: The RUNE experimental site in Denmark. The area of the coastal experiment is shown with the rectangle, and the positions of the meteorological mast at Hovsore with the circle marker and Copenhagen with the square marker. This area was selected because it is close to DTU's test station of wind turbines at Hovsore (position 2 in Figure 2 is 6 km north from the test station's main building), where we routinely perform wind-power measurements including those from a meteorological mast [15]. It is also a typical location of interest for offshore wind development. The site is well-serviced by a 4G network useful for device monitoring and data retrieval and needed for synchronization of the WindScanners. The Hovsere area is a nearly flat coastal farmland. A sand embankment separates the North Sea from the grasslands. Moving northwards, the embankment transforms into dune cliffs covered by grass. Close to position 3 in Figure 2, the terrain is \(\approx\)43 m above sea level (ASL). This is an important feature as lidars need a clear LOS to measure wind velocities, and such topography aids in performing measurements over the North Sea with small elevation angles from onshore locations [16]. The lidars of the prototype WLS200S are longe-range WindScanners. For convenience, we have given our lidars names (Table 1), and these will be used throughout this paper. The number in brackets behind a name denotes the position. Lidar Vara (pos. 2) was deployed centrally along the coast near the cliff, on the grass next to a church, Koshava (pos. 1) to the south in open grassland in front of a house, and Sterenn (pos. 3) to the north at one of the highest points, 20 m south of a lighthouse. The long-range profiling lidar Alize and the short-range profiling lidar WLS66 were installed next to Vara in pos. 2. Two other short-range profiling lidars, 3E and Bura, were installed inland at \(\approx\)250 m south, and \(\approx\)550 and \(\approx\)1200 m west of Sterenn in pos. 4 and 5, respectively. The location of the instruments was measured using a differential GPS system with an accuracy of \(\approx\)10 cm. More information about the site identification for RUNE can be found in [PERSON] and [PERSON] [16]. The topography of the area at a horizontal resolution of 1.6 m can be obtained via the website of the Danish Geodata Agency [17]. Land-cover data from the Corine dataset can be obtained via the website of the European Environmental Agency [18]. The land-use classes around the RUNE area are shown in Figure 3 and can be associated with an approximate surface roughness length \(z_{0}\) for mesoscale applications by using Table 1 in [19]. There, the yellow area (non irrigated arable land) is associated with a \(z_{0}\) value of 0.2 m. For open farmland with very few buildings and trees, which is the type of land-cover at the site, the European Wind Atlas recommends a \(z_{0}\) value of 0.03 m for microscale applications [20]. The differences between roughnesses for mesoscale and microscale applications are due to the applicability of the dataset; in mesoscale applications, the roughness has to be representative for a grid cell of a kilomet or more, which is often bigger than the local roughness due to the non-linear impact of obstacles on the flow. [15] found that the surface roughness at Hovsore is lower than 0.03 m and that \(z_{0}\) varies with season, direction, and atmospheric stability based on wind  
Figure 2: Topographic description of RUNE’s coastal experimental area based on a digital surface model (UTM32 WGS84, Zone 32V). The positions of the lidars are shown with different markers (see Table 1 for details). The colorbar indicates the height ASL.