Field measurements for the power spectral densities and spatial coherence of fluctuating wind speed near ground during typhoon ‘Muifa’

The wind characteristics of typhoon ‘Muifa’ such as power spectrum, cross power spectrum and coherence function are analyzed on the basis of long time measured data which is recorded respectively at the height of 10m, 20m and 40m above the ground in Pudong Shanghai, and two kinds of new cross power spectrum models are proposed based on Kaimal model. It is shown that longitudinal fluctuating wind power spectrum roughly fit with Von Karman spectrum, but there has deviation in high frequency band between lateral and vertical fluctuating wind power spectrum and Von Karman spectrum. By comparison, it can be found that measured fluctuating wind cross power spectrum is in agreement with modified Kaimal model. Averaged decay factor of 10min wind speed samples in longitudinal, lateral and vertical directions are 10.71, 7.43 and 8.63, respectively. In addition, the measured spatial coherence is consistent with Davenport’s empirical formula.