Research On Turbulence Detection And Signal Processing For Doppler Weather Radar

Disastrous weather has a great influence on flight safety.Doppler weather radar can detect and warn of extreme weather such as typhoon,turbulence and wind shear.At present,this important technique has been widely used.Because of the complexity and mutability of atmospheric environment,Doppler weather radar still has many technical problems,such as clutter suppression,velocity dealiasing and so on.Signal processing is an important part of Doppler weather radar system.Carrying out the research on signal processing technology is helpful to improve the performance of radar detection and has application value.This dissertation conducts a deep study on the methods of turbulence detection,velocity dealiasing and ground clutter suppression.The main contributions and innovations are summarized as follows:1.In order to improve the reality of simulation system,a simulation method for airborne Doppler weather radar turbulence detection is proposed.It is based on the correlation function using the Monte Carlo method.In this dissertation,Von Karman model and Dryden model are simulated.By comparing the theoretical analysis of the two models with the correlation of the simulated models,the turbulence model based on Von Karman model fits better with its theoretical characteristics.The three-dimensional atmosphere turbulence models meet the requirements of turbulence detection for airborne Doppler weather radar.2.In order to improve the accuracy of turbulence detection for airborne weather radar,a method of detecting turbulence for Doppler airborne weather radar is proposed.It is eddy dissipation rate(EDR)method.Simulation results show that EDR method not only related with spectral width,but also related with radar parameters and the distance from the radar.Compared with spectral width method,EDR method is not only applicable to the determination of turbulence region,but also to the classification of turbulence intensity.EDR method has higher turbulence detection accuracy.3.Based on the BoXPol radar measurements,the fuzzy logic hydrometeor classification(FHC)method for dual-polarization Doppler weather radar is analyzed.The combination analysis between polarization parameters and turbulence intensity are carried out to study the influence of turbulence on the hydrometeor type.The FHC method is used for hydrometeor classification.EDR method is used for turbulence detection.The results show that,when the turbulence intensity is large,the velocity and shape change in the falling process of precipitation particles will be imfluenced.This phenomenon is reasonable and accords with actual weather conditions.4.In order to detect and solve the velocity aliasing problem for Doppler weather radar Range Height Indicator(RHI)data,a method of three-dimensional model for correcting velocity ambiguity is proposed.Based on the characteristics of RHI,the cylinder model is built.The least squares estimation is used to estimate the Nyquist number.Compared with the linear extrapolation automatic method,the simulation results show that,this method works independent and can accurately calculate the velocity ambiguity value under different scales of wind field.And it is easy to calculate and has high application value.5.A clutter suppression method using parametric time domain method(PTDM)for multiple pulse repetition time(MPRT)technique is designed.This dissertation chooses 3 different pulse repetition time conditions for simulation and analysis.Compared with the Gaussian model adaptive processing method for normal single PRT sequences,the proposed method can provide better ground clutter suppression ability and higher estimation accuracy.Compared with the clutter filtering and spectral moment estimation algorithm for staggered 2-PRT sequences,the proposed method also can provide better ground clutter suppression ability.The proposed method can be improved for MPRT sequences.Compared with staggered 2-PRT transmission schemes with PTDM and the clutter filtering and spectral moment estimation method,the improved method presents better estimation accuracy under certain clutter situations.The results show that PTDM method improves the limitation of the conventional clutter suppression techniques and achieves the effective clutter suppression for MPRT sequences.