Long-term Trend Of Surface Wind Speed And Wind Energy Over China In Recent 36 Years

As an important climatic factor,wind is not only closely related to air pollution and sandstorms,but also an important climate resource.Wind energy is a new energy source with large reserves and wide distribution.Therefore,this paper analyzes the long-term trend of surface wind speed and wind energy over China in the past 36 years using the methods of linear tendency estimation and five-point moving average.The temporal and spatial variation characteristics of surface wind speed are analyzed from the aspects of mean wind speed and different wind speeds percentiles.The availability and stability of wind energy resources are analyzed from the aspects of effective wind speed frequency,frequency of prevailing wind direction,wind power density and coefficient of variation of wind power density.The results are as follows:(1)The annual mean wind speed in China showed a significant weakening trend,with a trend of-0.142m/s/10 a.The seasonal mean wind speeds all present decreasing trends and it decreased with largest trend magnitude in spring(-0.18m/s/10a),followed by winter(-0.135 m/s/10a),summer(-0.13 m/s/10a)and autumn(-0.129 m/s/10a).From the perspective of interdecadal changes,the downward trend in wind speed is slowing down.About 82% of the stations in China have a declining trend.The significantly declining trend of surface wind speed were found in the Tibetan Plateau and northeastern sub-regions among the seven regions classified in this paper.(2)There is a significant negative correlation between the annual mean wind speed and the annual mean temperature across China and each region,indicating that climate warming will lead to a decrease in wind speed.In the spring,when the surface wind speed is small,the temperature of 500 hPa(the height of the potential)increases in the northern of China,while the temperature(the height of the potential)decreases in the southern of China.Therefore,the gradient of the meridional thickness decreases in the northern part,which makes the zonal wind weaken at 500 hPa.And the weakening of the high-altitude winds in the sub-regions of plateau and northeast areas coincides with the surface winds,indicating that the reduction of wind speed at high altitudes leads to a decrease in surface wind speed to some extent.In addition,urbanization has little impact on the trend of surface wind speed in China.(3)The conversion of manual observation to an automated weather station has a greater impact on the small wind speed,and has no significant effect on the strong wind speed.From 1979 to 2003,except for the 5th percentile,the other percentiles showed a significant downward trend.From 2005 to 2014,the 5th,10 th,and 20 th percentiles of wind speed showed an increasing trend,the remaining percentiles showed a downward trend,and the overall change was less obvious.It shows that the weakening of wind speed from 2005 to 2014 is relatively weak from 1979 to 2003.(4)From 1979 to 2003,the annual effective wind speed frequency and annual average wind power density decreased by-3.15%/10 a and 9.44 W/m2/10 a.From 2005 to 2014,the annual effective wind speed frequency and annual average wind power density are significantly weaker than the previous period,which is-1.02%/10 a and-5.06 W/m2/10 a.This indicates that the weakening of wind energy resources has slowed down.