Research On The Retrieval Of Atmospheric Refractive Index Profile Based On Ground-based Microwave Radiometer And The Methods Of Improvment

The atmospheric duct is an anomalous structure,which traps electromagnetic waves in the waveguide layer.Therefore,it can be used to enhance the detection range of radar system or even achieve ultra-horizontal detection.And by the way,it will cause the change of electromagnetic shadow zone of radar.In the military,accurate and real-time acquisition of atmospheric duct parameters has a significant meaning for improving the operational performance of information equipment based on radio wave propagation.The atmospheric duct exists when the modified atmospheric refractive index profile is negative for the partial derivative of the height.Therefore,inversion of the atmospheric refractive index profile is a prerequisite for the solution of the atmospheric duct.As a passive remote sensing device,microwave radiometer has the advantages of unattended,uninterrupted,low-cost,high resolution vertically,and is an important means of atmospheric duct measurement.This thesis specifically analyzes the theoretical model of atmospheric microwave transmission of microwave radiometer and the basic principle of BP neural network training.Based on the five-year sounding data in Wuhan,BP neural network algorithm is introduced to inversion of the temperature and humidity profile as well as refractivity profile.The LMBP algorithm and particle swarm optimization algorithm are used to improve the learning mechanism and initial value determination respectively.Finally,the root mean square error of the inversion refractive index is reduced from 6.2N to 4.8N,and the inversion effect is obviously improved.Based on the above model,this paper uses RPG's measured brightness temperature data and measured temperature and humidity profile data to further verify the excellent performance of PSO-LMBP neural network for atmospheric refractive index profile inversion,and then select a group of RPG.The measured brightness temperature data,inversion of the atmospheric refractive index profile and the calculation of the atmospheric waveguide,improve the accuracy of the ground-based microwave radiometer inversion of the atmospheric duct.