Field measurements of typhoon characteristics near ground in Wenzhou coastal flat terrain

To gain the typhoon characteristics of wind filed near ground, a 10 m height field measurements wind tower station was set up Wenzhou coastal flat terrain. Series of wind parameters were measured during the passage of typhoon Fitow (2013) and Matmo (2014). Wind field characteristics such as mean wind speed, local wind axis, turbulence intensity, gust factor, turbulence integral scale and power spectral density were obtained for further investigate. The results show that, the wind speed profile index at 10 m height is significantly larger than the standard calculation value on the corresponding geomorphology in China, but the average and maximum wind speed are all much smaller than the standard values. The ratio of lateral turbulence and longitudinal turbulence are highly sensitive at different heights. The ratio increases with the height decreasing and both turbulence are different from the Chinese Standard. As wind speed and height tend to increase, the dispersion of the turbulence integral scale tends to increase linearly, but the median and mean value of turbulence integral scale only change slightly, the values of which are all less than the Japanese standard. With different typhoon, the longitudinal and lateral fluctuating wind power spectrums are different while the peak frequency and peak power are similar. Moreover, with change of magnitude, the value of fluctuating wind power spectrum and Von Karman will change, and the trends in change are similar