Radar Sea Clutter Propagation And Parameter Inversion Of Regional Non-Uniform Atmospheric Duct Based On WRF Meteorological Data Model

The 9-20 km tropospheric atmospheric stratification over the surface of the ocean is the main area where wind,rain,fog and other weather phenomena occur.The meteorological environment in this layer changes drastically,and the land-sea junction is susceptible to dry and warm flow on the shore,often causing the altitudinal refractive index changes abnormally at a certain height above the sea surface.The abnormal refractive index gradient causes the electromagnetic wave propagation trajectory to bend toward the surface of the earth,thereby trapping and propagating in the atmospheric duct layer,and realizing overthe-horizon propagation of ground wave in the troposphere.The atmospheric duct effect seriously interferes with the performance of radar detection,radio communication,electronic countermeasures and other systems in the marine environment.Studying its influence on radio wave propagation can help to compensate for system defects and to reduce the impact of uncontrollable factors such as meteorology.At present,the atmospheric numerical prediction model is developing rapidly,combining with meteorological numerical simulation technology,which could predict and simulate the physical parameters on the sea,can predict the structure of the atmospheric duct in a certain region on the sea surface.Therefore,this paper is of great significance for the prediction and inversion of the refractive index parameters of tropospheric ducts.In this paper,the electromagnetic wave propagation characteristics in the atmospheric duct environment are studied firstly.On this basis,the horizontal non-uniformity of the atmospheric duct environment is modeled,and the radar sea clutter is used to invert the modified refractive index profile of single azimuths,then the statistical estimation of the uncertainty of the profile parameters obtained by the inversion is calculated,finally,the evaporation duct height in different sea areas of China is calculated using the mesoscale numerical model WRF.The main work is as follows:The wide-angle parabolic equation model is used to calculate the propagation characteristics of electromagnetic waves in the duct environment,and the propagation characteristics of electromagnetic waves with different polarizations in evaporation duct and surface duct at different radar operating frequencies are calculated respectively.The sea mean scattering of HH polarization and VV polarization was calculated by using NRL model and GIT model respectively,and the radar echo power under different working frequencies and different scattering coefficients was calculated.The Kernel Principal Component Analysis(KPCA)method is used instead of the Principal Component Analysis(PCA)method to process the ill-conditioned nonlinear relationship between the refractive index profile and the radar echo more accurately.The modified refractive index profile is inverted using the radar echo power measured by the Qingdao Weather Radar Station in 2014,and the simulated annealing algorithm(SA)is used instead of the particle swarm optimization algorithm in the inversion process to avoid the global optimization process of the modified refractive index parameter fall into the local optimal solution.The four-parameter model of evaporation duct is introduced,and the four-parameter model of evaporation duct is sampled by Markov Chain Monte Carlo(MCMC)method.The posterior probability distribution of each parameter is calculated,and the uncertainty of parameter inversion results is obtained.The mesoscale WRF numerical model is used to simulate the meteorological physical parameters that have great influence on the atmospheric duct effect in some different sea areas(the East China Sea,the Yellow Sea and the South China Sea),and on this basis,the P-J single-parameter model is used to calculate the evaporation duct in different sea areas.Finally,the regional non-uniformity of the evaporation duct height is obtained.At the same time,the regional corrected refractive index distribution of the East China Sea,the Yellow Sea and the South China Sea was calculated.