## 2 Materials and Methods  
### Site Description  
The Scandinavian Peninsula, comprising Norway and Sweden, is shown in Figure 1a together with parts of Finland and Russia. The white colour shows sea level and the brightness from black to white shows terrain heights from sea level up to 2500 m. The peninsula is bordered by the Barents Sea, the Norwegian Sea, the North Sea and Baltic Sea to the north, west, south and east, respectively. Norway has a long coastline with several fjords and valleys that extend into the Scandinavian Mountains, a rugged landscape that is significantly different from Sweden where the terrain in general drops smoothly from this mountain range into the Baltic Sea.  
The regional terrain in Figure 1b shows the coastal terrain in northern Norway corresponding to the red rectangle in Figure 1a, and Fakken wind power plant is located at approximately 70\({}^{\circ}\) north latitude and 20\({}^{\circ}\) east longitude marked with a red rectangle in this regional terrain plot. There are several fjords and mountains that influence the wind at this point. Vannkista is 5 km west and has an elevation of 947 masal and Trolldalstinden is 12 km east (898 masal), both surrounded by similar mountains creating natural barriers to surface-level zonal wind. Starting about 20 km south-southeast, the Lyngen Alps are a dominant mountain range that has several mountains with elevations of 1500-1800 m, which drop abruptly into the 82 km long Lyngen Fjord to the east and 75 km long Ullsfjord to the west. These fjords are prone to meridional surface wind, and the mountain range can create lee spots in the fjords in cases of zonal wind in the atmosphere.  
An aerial photo of the Fakken wind power plant is shown in Figure 1c. The measured wind speeds are taken at 80 magl from a meteorological mast located at 70.099\({}^{\circ}\) N and 20.093\({}^{\circ}\) E at 60 masal, which corresponds to the red circle in Figure 1c. The park consists of 18 Vesta V90 3 MW wind turbines with a nacelle height of 80 magl, which are roughly located along two lines along a small hill with elevation increasing from 20 m to about 200 m starting just north of the mast and in a west-southwest direction. Note that the south line of wind turbines has a quite steep slope down to the sea level, and that the local terrain within the park has several small hills and depressions.  
In situ measurements of wind speed and direction are gathered using a Vaisala Anemometer WAA151 and Wind Vane WAV151, respectively. The mean, variance, minimum and maximum values are calculated every 10 min, and time-stamped at the start of the 10 min measurement period. A full year of data from 2017 is used to capture the yearly variation. Fakken wind power plant is in a sub-Arctic climate, where winter temperatures are moderated and mild for the latitude due to the warming effect of the Gulf stream, and the measurements and wind turbines are generally not affected by icing events. The average daily low and high temperatures vary from \(-6\) to 16 \({}^{\circ}\)C over the year. Due to the high latitude of this site, the wind is less affected by diurnal patterns. The site also has two months of midnight sun in the summer and two months of winter polar nights, where the sun does not dip below or rise above the horizon, respectively.  
Figure 1: \(Cont.\)