New European Wind Atlas: The Østerild balconies experiment

One of the main objectives of the New European Wind Atlas (NEWA) project is to carry out large scale field experiments at a high spatial and temporal resolution, and provide a significant upgrade to the experimental databases currently available. The Østerild balconies experiment aimed at collecting measurements over a relatively flat and semi-forested terrain to quantify the effect of various terrain features on the mean wind field. The experiment was performed at the Østerild test station for large wind turbines in Northern Denmark, from April to August 2016. The two 250 m meteorological towers available at the test site were equipped with balconies, first at 50 m above local ground level, later raised to 200 m. Scanning lidars were placed on each of the balconies, performing horizontal scans over 90° arcs with an east or west orientation depending on the incoming wind direction. The purpose of this study is to describe i) the new filtering method applied to the data, ii) the wind field reconstruction and the iii) utilisation of the derived wind fields to examine the imprint of surface heterogeneity on the mean wind flow. Cloud point data from aerial lidar scans were used to accurately derive the terrain and tree height. The mean wind flow patterns appeared to be heavily influenced by the terrain characteristics at the height of 50 m above ground level.