Wind Speed and Direction Profile Models in Typical Coastal Areas of China
Objective Wind speed and direction exert an important influence on atmospheric optical properties,and their vertical distribution and variation laws are of significance in astronomical observation,adaptive optics,and laser atmospheric propagation.Meanwhile,strong wind shear can trigger turbulence,and the transverse wind is closely related to thermal blooming.Since the natural environment is complex and changeable,wind speed and direction vary in different regions.Therefore,local wind speed and direction models should be established in practical applications.Due to the low accuracy of existing wind speed profile models and the lack of wind direction profile models,we analyze the variations of wind speed and direction in typical coastal areas of China,and propose novel wind speed and direction model functions respectively.We hope that the proposed wind speed and direction profile models are helpful to the design of adaptive optical systems,laser atmospheric propagation engineering,and free space optical communication.Methods First,by analyzing the daily data of 50 years of radiosonde data in typical coastal areas of China,the monthly average wind speed and direction profiles are obtained to study the monthly variation characteristics.Then,according to the monthly variation characteristics,the months in each season are adjusted,and the seasonal average profiles are acquired by statistically calculating daily data,with standard deviation at the corresponding height given.According to the seasonal average profiles,the coefficients of the model functions are obtained by genetic algorithm.Further,taking the average profile as the standard,the proposed models are compared with the existing models to verify that the accuracy of the proposed model is improved.Next,the standard deviation is adopted as uncertainty to analyze the variation characteristics of uncertainty with height.Results and Discussions 1)According to the variation characteristics of monthly average profiles of typical coastal areas in China,the wind speed profiles are divided into two types(Fig.1),and the wind direction profiles are divided into three types(Fig.2).2)The seasonal average profiles of wind speed show that the tropopause wind speed is generally high in winter and low in summer in the middle latitudes.The wind speed near 20 km at Dalian and Qingdao decreases to the minimum in summer,but the same phenomenon appears in winter at Xiamen and Xisha Islands.3)Employing the genetic algorithm,we obtain the fitting coefficients of the wind speed and wind direction model functions in different seasons(Tables 5 and 6).4)The established wind speed models are closely consistent with the average profiles,and the accuracy is significantly improved compared with existing wind speed models(Figs.4-8).The average relative deviations of established wind speed models of four seasons in Dalian are 1.35％,1.54％,1.12％,and 0.79％,respectively.While those are 2.92％,2.50％,3.29％,and 3.21％in Qingdao,2.28％,1.18％,1.06％,and 1.96％in Shanghai,1.82％,1.17％,2.56％,and 1.66％in Xiamen,2.80％,0.90％,0.98％,and 3.16％in Xisha Islands,respectively.5)The established wind direction profile models are closely consistent with the average profiles(Figs.9-13).The average relative deviations of established wind direction models of four seasons in Dalian are 0.53％,1.56％,0.67％,and 0.44％respectively.While those are 0.82％,1.30％,0.56％,and 0.59％in Qingdao,0.48％,0.78％,1.25％,and 1.07％in Shanghai,0.95％,1.06％,1.71％,and 1.81％in Xiamen,0.87％,1.04％,0.69％,and 2.70％in Xisha Islands,respectively.6)The variation trend of wind speed uncertainty is different from that of wind direction.The uncertainty of wind speed is generally the largest at the tropopause,while the uncertainty of wind direction is the smallest near the tropopause in Dalian and Qingdao,and the uncertainty of wind direction is more varied in other areas.However,the uncertainties of wind speed and wind direction have seasonal and regional varying characteristics.Conclusions 1)In typical coastal areas of China,the wind speed profiles are divided into two types,and the wind direction profiles are divided into three types.2)In our study,wind speed and direction vary with regions,months,and seasons.For optical engineering applications such as laser atmospheric propagation,the adoption of wind speed and direction models in local regions and corresponding seasons is more accurate.3)The proposed wind speed and direction model functions are universal in the typical coastal areas of China.The wind speed and direction profile models established in this paper have higher accuracy than the existing models.The mean relative deviation of wind speed is less than 3.29％,and that of wind direction is less than 2.70％.4)The statistical uncertainties of wind speed and direction have seasonal and regional characteristics.
atmospheric opticsprofile modelgenetic algorithmwind speedwind direction
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