Wind Field Characteristics And Wind Disaster Assessment Of Landfall Typhoons In South China

Typhoon is one of the most destructive natural disasters.The coastal area of South China is located in a typhoon-prone region,where typhoons may result in severe casualties and economic losses ever year.With the rapid development of economy and technology,more and more high-rise/super-tall buildings have been constructed in such areas which are demonstrated to be considerably sensitive to wind load.Information of typhoon wind field and typhoon-dominated extreme wind climate forms the basis for the wind-resistant design of building structures.However,much has been left to be further explored in related field in China.Typically,the observation data of typhoon is non-systematic and incomplete,which restricts in-depth and meanwhile targeted studies especially toward typhoons impacting China.Until now,studies on the key parameters of regional typhoons have been considerably limited,and the validity of assessment results of typhoon hazard needs to be verified.In this regard,this thesis presents a comprehensive study on the typhoon wind characteristics and typhoon-dominated extreme wind climate in South China,based on a large amount of data that have been collected by numerous well-maintained meteorological devices equipped in Guangdong and Hong Kong.The global wind field structures of Typhoon York,which impacted Hong Kong most severely in history,are studied first on the basis of field measurements detected by a Doppler radar wind profiler and several surface meteorological stations.The thermodynamics and kinematics characteristics of the typhoon throughout its whole depth are analyzed.The results show that the height of the typhoon's thermodynamic boundary layer depth is much smaller than the dynamical boundary layer height that is recognized by the maximum wind speed.It is interesting to find that the vertical profile of pressure deficit is linearly distributed along altitude.There is no positive correlation between the maximum wind speed(RMW)and Holland-B.In addition,the wind profile characteristics of nearly 20 typhoons in different incoming directions are investigated,and a vertical wind profile model similar to the turbulent wind spectrum is proposed based on the data.It is found that the topographic features have a significant effect on the wind profile.The height of gradient wind is between 450 m and1400m.The higher the average boundary layer wind speed is,the lower the gradient wind height tends to be.The proposed wind profile model is simple in form,has a good effect with the typhoon wind profile in the whole vertical range,and can reflect the characteristics of the Low-level jet.The following part focuses on the assessment of typhoon wind hazard.Quantitative analysis of the key parameters of typhoons impacting South China is conducted,with the help of long-term in-situ measurements of various meteorological records from 86 weather stations in Guangdong Province.More accurate data-driven models for the probability distribution function(PDF)of typhoon key parameters are established.On the other hand,Meng's typhoon wind field model is modified by using the proposed typhoon pressure field model in this study.The performance of the modified wind field model is then examined through comparison with field measurements.Based on the typhoon wind field model and the probability distribution of key parameters,typhoon-dominated extreme wind in South China associated with varied return period is estimated via the Monte Carlo sampling simulation method.It is found that there are some differences between the assessment results and the provisions stipulated in the wind load code of China.The results presented in this thesis are beneficial for further understanding typhoon structure and for better assessing typhoon wind hazard in South China,which is important for the wind-resistant design of civil structures especially in typhoon prone areas.