Quantification of the near-surface wind conditions of the African coast: A comparative approach (satellite, NCEP CFSR and WRF-based)

Abstract

The temporal and spatial variations of the near-surface wind conditions across the African coast are enormous due to local flow perturbations from changes in sea surface roughness or/and the weather system processes driven mainly by the Atlantic and Indian Ocean Currents. Over the past decades, the patterns of the near surface wind speed and directional flow have significantly changed across the globe. To quantify the long-term changes of the surface wind conditions off the African coasts, the spatial distributions of historical wind climates and analyzed surface temperature from remote sensing and two atmospheric models are presented. Thus, the offshore wind conditions variability derived across 4 coastal zones are quantified through a comparative approach. Over period of 2001–2010, the trends of regional-scale wind conditions from the numerical model of NCEP CFSR and satellite observations of CCMP are assessed. For identification of geographical viable locations with concentrated energy resource and negative temperature gradient, the surface wind conditions are adjusted to offshore turbine generator (V80 2 MW) operating height of 100 m. Based on statistical evaluation of the offshore wind condition, graphical representations of the historical wind climate are presented. Furthermore, the monthly and seasonal sectorwise winds at 10 and 100 m ASL for 2002 are compared in determining how local perturbations had caused a drift in offshore wind flows within the boundary height of 100 m. On local-scale evaluation, the near-surface wind conditions derived from WRF are validated with NCEP and CCMP datasets. The long-term historical wind conditions in time and space revealed that the satellite, WRF and NCEP models are reliable tools in replication of the coastal wind conditions across the coasts of Africa. Results also indicate the southeast coast to be an energetic region with concentrated mean wind energy flux between 300 and 1580 W/m2 (8.10–13.70 m/s), but subjects to coastal variations of strong weather processes. No persistent wind pattern was found when considering the variability of near-surface wind conditions from a low to high latitude.