The Wind Turbulence of the Near-surface Layer of Jiangsu Coastal Area and Its Response to Typhoon

In order to study the influence of wind turbulence characteristics on the rational and safe development and utilization of wind energy resources, long-term wind gradient observations are carried out in Jiangsu with five wind towers along the beach. Based on the wind speed and wind direction observations for 42 consecutive months from June 2009 to November 2012, temporal and spatial variation characteristics of the surface layer wind gust factor and turbulence intensity are analyzed. Variation characteristics of gust factor and turbulence intensity with wind speed, the influence of land and sea distribution on gust factor and turbulence intensity are then discussed. Seven typhoons that have great impacts on Jiangsu are selected, including the rare typhoon Damrey in 2012 that landed in Jiangsu, and the typhoon's influence on the wind is discussed. Results show that the gust factor and turbulence intensity are strong at the height of 10 meters, in the coastal areas of Jiangsu. The annual average gust factor of 10 m and 70 m heights in the coastal areas of Jiangsu are 1.50 and 1.24; the turbulence intensities are 0.20 and 0.11, respectively. The frequency distribution of gust factor and turbulence intensity is unimodal. At lower observation heights, the frequency distribution is wider, the peak is lower, and the peak is biased toward the high value area. The influence of sea and land distribution is obvious. The turbulence intensity of offshore wind is significantly greater than that of onshore wind. The wind speed has a significant impact on gust factor and turbulence intensity, which decrease with the increase of wind speed. When a wind greater than strong breeze happens, the gust factor and turbulence intensity are basically stable and less variable. Near the typhoon center, the wind speed has a bimodal change of increasing-subtracting-increasing, and the wind direction changes rapidly in a short time. The turbulence intensity at 10 m and 70 m heights are 0.25 and 0.14, the gust factor at 10 m and 70 m heights are 1.65 and 1.33, much larger than the value around typhoon and without typhoon. During the passage of the typhoon center, the turbulence intensity and gust factor do not decrease with height and they increase between 30 m and 50 m. When the wind speed increases, the turbulence intensity and gust factor decrease overall, but local peaks may occur when the wind is strong breeze to moderate gale while the typhoon center passes, threatening the safety of the turbine.