Evaluation on the Trends of Global Wind Resource and Its Variability

In our previous work, we demonstrated that the Robust Coefficient of Variation (RCoV) is an effective metric to assess wind-speed variability. In this study, we further apply the metric to identify regions in the world that favor wind-energy development. Specifically, RCoV is defined as the median absolute deviation from the median, divided by the median. We derive and use the wind speed at 80 m above surface between 1980 and 2017 from the MERRA-2 reanalysis dataset. We analyze the daily, monthly, and yearly average wind speeds and their RCoVs at every grid point in the world. In general, the trade winds have strong influence on wind-speed variabilities in the tropics across averaging time scales. Coastal regions have strong diurnal wind-speed variations, including the Mediterranean Sea, the northern part of Indian Ocean, south and southeast Asia. Considering the magnitude of RCoV, most of the world experience weaker variations in wind speed year to year than daily or monthly variations. To study the long-term trend of the global wind resource, we also analyze the changes of wind speed and its RCoV from 1980 to 2017. Moreover, we evaluate the effectiveness of other statistic metrics, for instance, standard deviation and Weibull parameters, on assessing wind-speed variabilities. Overall, other than central United States and Europe, regions with strong and consistent wind resources over 38 years include eastern and southern parts of South America, regions surrounding the Red Sea, and Australia. In this study, we offer a comprehensive picture of the global wind resource by accounting for its long-term wind-speed variabilities.

Figure 1: (a) The median of the daily mean wind speed at 80 m above surface between 1980 and 2017; (b) The wind-speed RCoV of daily-mean, (c) monthly-mean, and (d) yearly-mean wind speeds over 38 years. Large values of RCoV represent high wind-speed variabilities, and vice versa.