Research On The Wind Characteristics Of China Coastal Area

China coastal area is frequently affected by strong wind caused by tropical cyclone and cold wave every year. The strong wind caused by them often brings severe disaster, but sometimes it also offers plenty of wind energy resource and water resource. It is worthwhile to make use of the abundant wind energy brought by the strong wind of tropical cyclone and cold wave as we defend the disaster caused by them. Statistically analyzed result of wind data from 91 anemometer towers of coastal 11 provinces, cities and municipality during 2009.6.1-2010.5.31 are statistically analyzed to give an analysis on the basic wind characteristic of the China coastal area. The above data is observed by conventional instrument. However the conventional instrument can only achieve horizontal information, parameters such as slope angle, vertical turbulence intensity and turbulent spectrum are satisfied only based on the three-dimensional ultrasonic anemometer data. Based on the ultrasonic anemometer data from four stations of China coastal area, wind characteristic of four tropical cyclones: Morakot, Molave, Soudelor, Koppu and three tropical cyclones: Meranti, Fanapi, Megi which landed on coastal area in 2009 and 2010 respectively and a cold wave during March 2010, in Fujian province were studied. The main results of the calculation and analysis are as below:(1) Ultrasonic data contains various deviations, so the pre-processing is very important. The pre-processing in this article includes eliminating the inefficient data and the wild point, disposing the other abnormal data, coordinate rotation, eliminating the tendency term. All above steps are taken to ensure the accuracy of the data. The step eliminating the wild point includes: conform a new time series to eliminate the isolated wild points, compare the standard deviation and average data to eliminate other wild data. In this way it is possible to reserve the gale data while assuring the data reliability. Conventional instrument data and ultrasonic anemometer data during a typhoon and cold wave are compared and the result tells that the two data is consistent, it means the pre-processing of ultrasonic data is successful and efficient.(2) The analysis based on coastal area wind parameter such as the annual average wind speed, turbulence intensity, wind shear exponent shows that China coastal area is abundant in wind energy and has good conditions for exploiting the wind energy.(3) During typhoon affecting time the wind speed and wind direction have evident change, the wind speed decreases as the station gets farther from typhoon or as the typhoon weakens, this change is more intense if the station is closer to typhoon. The wind direction turns clockwise (anticlockwise) when the station locates on the right (left) side of the typhoon, the wind direction changes intensely when the wind speed has intense change. The largest slope angle occurs when the wind speed is lower and the change is severe. Turbulence intensity gets greater during the initial stage of typhoon affecting time, before landing the turbulence intensity decreases as the wind speed increases but after landing turbulence intensity change is in consistent with wind speed or shows no obvious change. Different typhoon shows different characters. The gust factor is in good consistent with the turbulence intensity. Most examples indicate that it is vortex with short period: about 10s during typhoon and vortex with long period before and after typhoon, the space scale is determined by wind speed and time scale. The turbulent spectrum shows isotropy and the slope is -5/3 in inertial area during strong wind.(4) The cold wave analysis in this article shows that the wind speed has obvious change but the wind direction doesn't change obviously. Turbulence intensity appears transverse>longitudinal>vertical orientation or landscape orientation nearly equals longitudinal orientation. Gust factor and turbulence intensity are in consistent variability. It shows short lifecycle and large space scale vortex and the turbulent spectrum shows isotropy and the slope is -5/3 in inertial area.