Comparison of wind speed produced by AROME+WAsP to wind measurements

For verification of the model system, some Helsinki testbed tower stations were checked and some new towers were erected or new wind sensors installed in existing towers in 2008. In order to verify the method for predicting small-scale local wind energy potential, the wind data produced by the operationally run AROME for the period 1 June 2008 - 31 September 2009 were used as input data for the WAsP model. Wind data produced by AROME from the nearest grid point of measurements masts and from one altitude (80 or 100 metres above ground level) were used. This method deviates from the method applied for the Finnish Wind Atlas, which used lib-files produced from AROME's wind data as input for the WAsP.

When using WAsP, zero displacement and obstacles near the measurement masts were taken into account. Roughness maps were made on the basis of CORINE (Coordination of Information on the Environment) land use data. The resolution of the CORINE maps was 25 metres and that of the topographic maps was 10 metres.

Table 1 represents the wind speed difference between mast measurements and the AROME+WAsP results for the entire reference period in summer (from June to September) and in winter (from November to March). The average wind speeds obtained for the mast measurements are also shown.

There was very good agreement between the AROME+WAsP results and measurements made at Isosaari and Vänö. The difference between measurements and the AROME+WAsP results varied by mast site in the costal area. The difference was greatest for Åland, while the difference between measurements and the AROME+WAsP results inland was about one per cent.

Figure 1 shows the vertical wind profile for Isosaari. The figure has two vertical profiles derived from the AROME+WAsP method. One vertical profile was made by using the CORINE roughness map when a lib-file was produced and another by using AROME's own roughness map, which corresponds to the Finnish Wind Atlas method. The picture shows that the difference between measurements and the results obtained with the Wind Atlas method using the AROME map is less than the corresponding difference obtained using the CORINE map.



Figure 1. Vertical wind profile for Isosaari derived from the AROME+WAsP method.



Table 1. Wind speed difference between mast measurements and AROME+WAsP results.