  High frequency wind time series measured at different heights from the ground
(from 1.5 to 25.5 meters) in an urban area were investigated by using the
variance of the coefficients of their wavelet transform. Two ranges of scales
were identified, sensitive to two different dynamical behavior of the wind
speed: the lower anemometers show higher wavelet variance at smaller scales,
while the higher ones are characterized by higher wavelet variance at larger
scales. Due to the relationship between wavelet scale and frequency, the
results suggest the existence of two frequency ranges, where the wind speed
variability change according to the position of the anemometer from the ground.
This study contributes to better understanding of the high frequency wind speed
in urban areas and to a better knowledge of the underlying mechanism governing
the wind fluctuations at different heights from the ground in particular in
urban area.
