Research On Change Characteristics Of Wind Speed At Mid-low Altitude Layer Over China

To provide the scientific references for the development of the wind energy resources in China,the radiosonde wind speed data at 5 mid-low altitude layers including 500 m,100m,1500 m,2000m,3000 m from 1981 to 2014 are used from 93 meteorological sounding stations which are distributed throughout the country and divided into seven climatic areas.Firstly the climatic characteristics of wind speed at every layer for the whole country and seven areas are analyzed,including annual average wind speed,monthly average wind speed and their vertical shear,and the spatial distribution maps of the annual and the seasonal average wind speed are drawn.And then it is analyzed that the climatic change characteristics of wind speed at each layer for each areas which includes change trend,abrupt change and periodical variation of the average wind speed,and the spatial distribution maps of trend of the yearly and seasonal average wind speed are drawn.The following conclusions are obtained by the thesis: 1.the highest annual average wind speed is at the Northeast China,especially near the Changbai Mountain.For the rest areas,the annual average wind speed shows the decrease trend from coastal areas to inland and from east to west and get the lowest near the Sichuan Basin.The distribution characteristics of the seasonal average wind speed are basically same with annual average wind speed,the essential characteristics are the average wind speed is high in the spring and low in the winter or summer below 1000 m,but with the increase of the altitude to 1500 m,the highest average wind speed appears in the winter instead of the spring,with this the average wind speed in the winter become the leading character for the annual average wind speed.2.The annual average wind speed increases with height,especially in the winter the increasing rate is the most rapid,meanwhile the increasing rate is slower in the summer,which results in the average wind speed in the winter is much higher than that in the summer on the layers of 2000 m and 3000 m.3.In Northeast China and East China,the annual average wind speed on the all 5 layers have the decreasing trend,but only on the layer of 500 m in Northeast China the trend passes the significant testing(the significant level a=0.05).In all layers of the other 5 areas,there are both increasing trends and decreasing trends.The proportion of the total stations number of the decreasing trends is more than that of the increasing trends,and same with the passing rate of the 0.05 significant testing.But in a whole,there are no significant changing trends of the annual average wind speed on mid-low layer over China.4.For annual average wind speeds all over China,there are mainly decreasing trends below 1500 m,and equally increasing trends in northern parts and decreasing trends in southern parts above 2000 m.For the seasonal average wind speeds,changing properties are almost similar all with decreasing trends in summer and fall,and increasing trends in spring and winter.5.The abrupt times are mainly concentrated near 2010 and 1980's,that is the beginning and the end of sequence,there are less abrupt events between them?6.The periods of the annual average wind speed on different layers in all zones are concentrated in 2~6a,in which quasi-2a periods appear in the 1980 s and quasi-4a periods appear from the late of 1990 s to the early of 21 th century.