The Fractal and Chaotic Characteristic of Gustwind
Cheng Xue · Climatic and Environmental Research · 2007
We first investigate a typical case of serious gustwind(March,2003 in Beijing) by the use of wind speed series recorded by the Beijing 325 m Meteorological Tower.The structure,especially the fractal characteristic of the gustwind can be very well and very clear represented by the fractal theory,which leads to some essential information about such phenomenon.Then we also investigate all cases of gustwind as well as turbulence,raining weather and weak wind(in such case there is no gustwind) in the whole year 2002.The comparisons reveal: 1)The wind gustness appears when the basic flow(e.g.,ten minutes averaged velocity) and the perturbations(fluctuations) both are strong.It perhaps can be explained by the non-linear interactions between large-scale structure(ten minutes average velocity) and the perturbations(original data).2)As the fractal dimensions of the wind gustness on different heights are calculated,there is often a turning point in the fractal dimensions at the time scale of 16.7 hours.It means the wind gustness is multi-fractal.3)The fractal dimensions of different gustwind are different,unlike the turbulence whose fractal dimension is almost in 1.6—1.7.It means the wind gustness is anisotropy but not isotropy as turbulence.4)By analyzing no gustness of wind and comparing with gustwind time scales,we also find that there are two relationships between the probabilities with fractal dimensions.