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 a useful statistic to quantify wind-speed variability. In this presentation, we further apply the metric to identify global regions in the world that favor wind-energy development. RCoV is defined as the median absolute deviation from the median, divided by the median. In this analysis, we use the daily, monthly, and yearly average wind speeds at 80 m above surface between 1980 and 2017 from the MERRA-2 reanalysis dataset. To study the trend of the global wind resource, we analyze the changes of wind speed and its RCoV from 1980 to 2017. Herein, we spatially contrast the median wind speeds and the RCoVs between two 10-year periods, 1980 to 1989 and 2008 to 2017 (Figure 1). In general, the trade winds have strong influence on wind-speed variabilities in the tropics across averaging time scales. Moreover, most of the world experience weaker variations in wind speed year to year than daily or monthly variations. For long-term trends, the tropics experience some of the largest changes in wind speed and its variability between the 1980's and the 2010's. Although the global trends in daily changes of winds are mild, many parts of the world record stronger monthly and yearly variations in the past decade, such as central and eastern Africa, central United States, and northeast South America. We also 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 provide a comprehensive picture of the global wind resource by accounting for its long-term wind-speed variabilities.

Figure 1: The normalized differences in percentage between the periods of 1980 to 1989 and 2008 to 2017 of: (a) the median of the daily mean wind speed at 80 m above surface; (b) the daily-mean wind-speed RCoV; (c) the monthly-mean wind-speed RCoV; and (d) the yearly-mean wind-speed RCoV. Positive values (black) represent the 2010's having stronger wind speeds in (a) and stronger wind-speed RCoVs in (b), (c), and (d) than the 1980's.