Development Of Lidar System For Monitoring Turbulent Profiles On Shipborne Platform

The distribution of atmospheric turbulence in a specific direction,which is the distribution of the refractive index structure constant of atmospheric turbulence along the path,is a crucial factor in determining how path turbulence affects laser engineering applications.In offshore laser engineering applications,a crucial factor for the optimal adjustment and measurement to evaluate the effectiveness of offshore laser atmospheric transmission equipment is the intensity distribution of atmospheric turbulence at finite distances along a specified path,which is accurately obtained in real-time.This dissertation focuses on the development of a turbulence profiling lidar that can be applied to shipboard platforms,which offers an efficient tool and approach for the investigation of offshore turbulence.The main work accomplished in this dissertation is as follows.1.The technical challenges that need to be solved when measuring shipborne are analyzed and discussed,and the design requirements and design plan of the turbulence profile lidar system for shipborne platforms are analyzed and clarified in conjunction with the shipborne measurement environment,and the development and construction of the system were completed.To provide reliable and accurate measurements of the distribution of air turbulence intensity along the specified path offshore in the harsh and complicated environment.Firstly,the developed shipboard turbulence profile lidar system combined with resistance to ship’s bumpy impact,resistance to marine high humidity and high salt environment and the suitability of key components for marine environment were analyzed and evaluated,and the development and construction of the system was completed.Secondly,sea field experiments in the Bohai Sea region were conducted to confirm the developed lidar system’s marine applicability.Lastly,for the special measurement scenarios such as horizontal angle,different sway correction stabilization schemes were simulated and evaluated with the measured data,and the development and construction of the sway correction stabilization system was completed,and the assembly and commissioning of the shipboard turbulence profile lidar were completed.2.The turbulence profiling lidar system’s noise model is examined and refined down to a single pixel.The significance of this model is that it can quantify and analyze the errors in the measurement results of the atmospheric turbulence characteristic parameters caused by the inherent noise of the system and the sky background noise during the measurement process.This model is significant because it can quantify and evaluate errors in measurements of the atmospheric turbulence characteristic parameters that are produced by system noise and sky background noise.By analyzing the detection results under a specific parameter and conducting a series of noise addition,multiplication,denoising,and calculations to achieve a more accurate result by correcting the detection results,the simulation study evaluates the noise-induced bias in the detection results.Actual measurements are used to verify the noise model-based correction method.The method serves to increase the upper limit of the detection distance that the lidar detection system can detect as well as the accuracy of the detection results of the turbulence profile lidar system.3.On the basis of the variance in integration weights,a method for inverting turbulence profiles in real time was proposed.Firstly,the turbulent atmospheric characteristic parameters are measured using the differential image scintillation method and differential image motion method based on the turbulent lidar backscattered echoes.Secondly,the experiments of multi-beacon horizontal direction observation and airborne beacon slant direction observation were also carried out to verify the reliability of turbulence parameters measured by the lidar system.Lastly,a method of real-time inversion of turbulence profiles based on the differences in integration weights is presented and theoretically validated by merging the near-surface turbulence model and evaluating the integration weights of turbulence characteristic parameters.4.Long-term observation and comparison experiments were conducted using the proposed method for real-time inversion of turbulence profiles based on the difference of integration weights to verify the feasibility and accuracy of the proposed method.Results that are consistent with the theoretical analysis can be seen after comparing and analyzing the turbulence profiles acquired by the inversion method under various typical weather circumstances.Based on the results,synoptic observation experiments using micro-thermometers at Hefei are also done,as well as shipborne experiments in Bohai Bay.The experimental results demonstrate that,under a variety of atmospheric turbulence intensities and meteorological circumstances,real-time turbulence profiles generated using the suggested inversion methodology for a 1000 m long measurement path may properly depict the path turbulence distribution.The linear correlation coefficients are 0.887 and 0.923 in different regions,and the deviations are within acceptable limits in most cases,which demonstrates the feasibility and efficiency of the proposed methodology.