Analysis On Variation Characteristics Of Vertical Wind Speed In Urban Canopy Of Shenzhen

With the continuous acceleration of urbanization and the increasing number of high-rise buildings in Shenzhen,the bad impact of strong vertical wind caused by extreme weather has gradually increased.In order to explore the change rules of vertical wind speed with height change in Shenzhen,and prevent the hidden danger that highrise buildings cannot withstand strong winds when disasters such as landfall typhoons,this research has developed.Based on the hourly wind speed observation data of Shenzhen Meteorological Gradient Tower,Ping An Building and Central Park automatic station from 2016 to 2019,this study discussed the relationship between height and vertical wind speed,which are including 10-minute average wind speed(average wind)and 3-second average wind speed(gust wind).After all dataset samples in the study grouped by bottom wind speed,the fitted Hellman coefficient values for each group were obtained due to the power law and least squares fitting methods.The results show that: both gust wind and average wind speed increase with the rise of height,following the Hellman exponential law.And the relationship between the fitting Hellman coefficient and the gust wind speed or the average wind speed both obeys the exponential decay function.When the wind speed reaches the corresponding high percentile level,about 80%,the Hellman coefficient remains almost unchanged.At the same time,the study found that the Hellman coefficient of urban areas is generally higher than that of rural areas: in the urban area,the Hellman coefficient of gust wind ranges from 0.49 to 0.169,and the that of average wind is 0.64 to 0.327;in rural areas,the Hellman coefficient of gust wind ranges from 0.33 to 0.077,and the average wind ranges from 0.49 to 0.153.There is an apparent diurnal variation of the Hellman coefficient,which is lower during the daytime and higher during nighttime.Affected by the urban climatic conditions and the urban heat island effect,the monthly variation of the urban Hellman coefficient is not obvious,and the effect of precipitation on the Hellman coefficient is different under the two terrain conditions.This study can provide an effective reference for the prediction of wind speed in vertical direction and potential risk assessment in Shenzhen.