Estimation Of Atmospheric Optical Turbulence Profile Based On Thorpe Scale

Turbulence is one of the most popular and widely used phenomena in nature.Atmospheric turbulence will produce various turbulence effects on the light waves transmitted in the atmosphere,while the measurement of atmospheric optical turbulence intensity is the atmospheric refractive index structure constant.At present,there are a lot of direct measurement techniques,but these measurement methods inevitably need to pay a large price,so the relationship between atmospheric turbulence intensity and conventional meteorological parameters is established.It is an important research area to estimate the profile of atmospheric optical turbulence by using the conventional meteorological parameters which are easy to measure.At present,a great deal of work has been done on atmospheric optical turbulence profile model at home and abroad.In addition to the empirical model of atmospheric turbulence profile obtained by piecewise fitting of atmospheric optical turbulence profile data on the basis of experiments,there is also a basic turbulence theory,which is based on the empirical model of atmospheric turbulence profile.Based on the Tatarski formula of the relationship between the profile and the profile of the conventional meteorological parameters established by the outer scale,a variety of external-scale models are derived.The Thorpe scale in the Thorpe outer scale model is proposed by Thorpe in order to quantify the scale of water turnover.This method has been widely used in oceanography,mainly to study and analyze the turbulent mixing of water,and to estimate the turbulent mixing parameters(energy dissipation rate,diffusion coefficient).In the field of atmospheric science and fluid dynamics,it is mainly used to distinguish turbulent mixing region and estimate different turbulence parameters in fluid,but it is rare to use Thorpe scale to estimate atmospheric optical turbulence intensity.This paper makes a statistical analysis of the sounding survey data of Korla,Lhasa,Tibet and Maoming,Guangdong Province,and estimates the profiles of the above three areas by using the Tatarski formula on the Thorpe scale,and compares them with the measured data to judge the validity of Thorpe scale estimation.Based on this method,the method is first used to estimate C2 of the South Pole,which has not yet been measured by the profilometry,and is applied to the location of the Antarctic astronomical site.The main work of this paper and the conclusions obtained are as follows:(1)Based on the statistical analysis of the measured data of Korla,Lhasa Tibet and Maoming coastal area in Guangdong Province,the Cn2 profiles of the three places are obtained.It is found that the day profiles of the three places are 1?2 orders of magnitude larger than those of the nighttime ones.In the range of height considered(0?25 km),the average profile will fluctuate in varying degrees,but generally the fluctuation range of turbulence at night is larger.All of these phenomena clearly show the diurnal differences of the average profiles of the three regions.In the near-surface layer,the mean Cn2 profile decreases faster in Lhasa than in the other two regions,and the relative height of the minimum value is also lower than that in the other two areas.The mean Cn2 profiles of Lhasa and Maoming show obvious bulging near 15 km,but there is no obvious drum in Korla area.All of these phenomena clearly show the regional differences of the average profiles of the three regions.(2)Based on the Tatarski parameterization scheme and the Thorpe scale method,the Cn2profiles of Korla,Lhasa Tibet and Maoming coastal areas in Guangdong Province are estimated.The estimated values and measured values show good consistency in both the order of magnitude and the overall trend of the profiles.Especially in the height range of 5-20 km,the estimated values can capture the details of turbulence changes well.Moreover,the quantitative statistical analysis shows that the correlation between the Thorpe scale estimation results and the measured results in Korla,Lhasa and Maoming seaside is 69%,68%,60%,respectively,and the average relative error is less than 5.0%.All of these results show that the Thorpe scale method is feasible to estimate the optical turbulence profile.(3)By means of the downloaded data of the conventional meteorological parameters at the South Pole,combined with the Tatarski parameterization scheme and the Thorpe scale method,the contour lines of the South Pole in summer and winter are estimated,and the atmospheric coherence length,seeing,isoplanatic angel are calculated.The seeing above and within the boundary layer and their integrated contribution for the whole layer(0?25 km),and compared with the other literature results.The comparison results show that the C2 estimated decreases rapidly with height near the ground,slowly decreases after 300 m,a bulge appears after 5 km,and decreases steadily after 10 km.And they are characterized by the fact that most of the turbulence is concentrated below 300 m.The Thorpe scale estimates:the average seeing is 1.87" and the seeing below the 270 m is 0.39 H in winter above South Pole,which is well agree with the results of other scholars.Based on the Tatarski parameterization scheme and the Thorpe scale method,the Cn2 profiles of the above areas can be well estimated,but the changes of the detailed structure of the atmospheric optical turbulence profiles at some altitudes are not fully consistent.It also needs a large number of measured data to further improve the Thorpe scale method.If the resolution of the sounding data can be improved,it will also be helpful to improve the estimation effect of the Thorpe scale method.In addition,the results of this paper are mainly based on the limited sounding data in the above areas.For the feasibility of Thorpe scale in other areas,it needs long-term data accumulation,which needs to be further verified.