Analysis of Near-Surface Turbulence in Plateau and Desert Regions Using HAP Model
Objective We aim to enhance the accuracy of assessing turbulence effects on laser atmospheric transmission in plateau and desert regions.Deserts and plateaus serve as important application scenarios for laser atmospheric transmission.Due to their unique geographical and climatic conditions,these regions typically exhibit high transmittance,high wind speeds,and relatively low absorption coefficients.Consequently,the influence of atmospheric optical turbulence becomes the dominant factor,while atmospheric attenuation and thermal halo effects are generally minor.In-depth research on the height distribution of atmospheric optical turbulence in plateau and desert regions is crucial for improving the application of laser atmospheric transmission.Methods To capture the vertical distribution of turbulence intensity near the ground,we conduct simultaneous measurements of optical turbulence at two ground elevations(2 and 5 m)in plateau and desert regions,supplemented by aerial surveys using unmanned aerial vehicles equipped with micro-temperature sensors.We first estimate the refractive index structure constant at a height of 5 m using the measured data at 2 m and local sunrise and sunset times,comparing the results with measured values.Furthermore,we extend the prediction of the refractive index structure constant to a range of 150 m near the ground using the HAP model,comparing these estimated values with profile data from unmanned aerial vehicles.We then re-fit the key parameter—exponentialp—in the HAP model to optimize its predictive performance.Finally,we conduct a comprehensive evaluation of the newly fitted HAP model to ensure it provides more accurate and reliable turbulence intensity predictions in practical applications.Results and Discussions 1)The refractive index structure constants at both altitudes in plateau and desert regions exhibit significant"Mexican hat"diurnal variation characteristics(Fig.2).The structure constant is generally larger in plateau regions compared to desert regions,with slightly longer periods of strong turbulence.During the daytime,the variation trend of refractive index structure constants is consistent across different heights in both regions;however,this correlation weakens at night.2)In our study,the traditional HAP model estimates the refractive index structure constant at a height of 5 m,which aligns well with measured values(Fig.5).The estimated values agree closely with measured values in magnitude and trend,though the HAP model tends to underestimate values from 3 h after sunrise to 4 h before sunset,coinciding with peak turbulence.When applied to air profile estimation,the HAP model shows poorer agreement(Fig.6),indicating a need for further optimization.3)The newly fitted HAP model estimates the refractive index structure constant at 5 m and shows improved agreement with measured values(Fig.7).The results indicate that the estimated values from the new model closely align with the measured values in both magnitude and trend,demonstrating a significant improvement compared to the traditional model.Notably,the newly fitted HAP model enhances the agreement between estimated results and measured values when estimating the air profile(Fig.8).4)A comparison of subsequent data analysis using the traditional and newly fitted HAP models(Fig.9)clearly shows that the estimation results from the newly fitted HAP model are more consistent with the measured values,significantly enhancing the accuracy of the model's estimations.This improvement not only enhances the predictive capability of the model but also provides greater accuracy for evaluating the turbulence effects on laser atmospheric transmission in plateau and desert regions.Conclusions 1)The correlation coefficients between the estimated and measured values of HAP model are 0.934 and 0.943,respectively,with root-mean-square errors of 0.165 and 0.150.However,the model's consistency in air profile estimation declines significantly.2)For the HAP model at 5 m altitude in plateau and desert areas,correlation coefficients increase to 0.965 and 0.978,respectively,and root-mean-square errors decrease to 0.086 and 0.101.The air profile estimated by the new HAP model aligns well with measured values.The new HAP model provides a more accurate method for estimating the atmospheric optical turbulence profile distribution in the boundary layer over the plateau and desert regions,and thus offering new possibilities for improving the evaluation accuracy of laser atmospheric transmission in these environments.
atmospheric optical turbulenceplateau and desert regionslaser atmospheric transmissionnear-surfaceHAP model
NETL
NSTL
万方数据
