Directional calibrated wind and wave reanalysis databases using instrumental data for optimal design of off-shore wind farms

An important part of the future expansion of wind energy utilisation will come from offshore sites. The economic viability of offshore wind farms depends on the favourable wind conditions compared to sites on land, compensating the additional installation and maintenance costs. For project planning and sitting, especially for large projects, a reliable prediction of the wind resource and wave climate is therefore crucial. In this work, two new wind and wave reanalysis data bases (W2RDB) developed by the University of Cantabria are presented. They constitute a powerful tool for the design of offshore wind farms, offering important advantages for the statistical characterization of wind sites (continuous time series, good spatial coverage, constant time span, homogeneous forcing, long time series). However, W2RDB are not quantitatively perfect and corrections using instrumental observations must be addressed before they are used, this process is called calibration. The calibration is especially relevant near the coast and in areas where the orography is complex, since in these places the inaccuracy of W2RDB is evident mainly due to the insufficient forcing resolution. The quantitative differences between numerical and instrumental data suggest that different corrections should be applied depending on the mean direction of wind and waves, respectively. This work focuses on the calibration performed based on a nonlinear regression problem where the corresponding correction parameters vary smoothly along the possible mean wave directions by means of cubic splines. The correction of wind speed and significant wave height is performed using instrumental data: i) buoy records and/or ii) satellite data.