Study On The Attenuation Correction Of Dual-Pol Radar Based On Differential Propagation Phase Shift

Meteorological radar is widely used in disaster reduction and disaster early warning as an important means to detect meteorological environment,it evaluates the characteristics of the weather target according to the change of the echo.The rainfall on the path will give rise to the reflectivity attenuation,leading to estimating meteorological characteristics of detecting target unaccuratly,it may also drown rear rainfall area.The attenuation is more severe for the lower frequency such as X-band,In order to accurately analyze the true characteristics of meteorological targets and improve the accuracy of precipitation estimation,it is indispensable to correct the attenuation.Dual-polarization Doppler radar can provide a differential propagation phase shift that characterizes the microphysical properties compared with conventional radars.There is a high correlation between the specific differential propagation phase shift and the rainfall rate,but also the differential propagation phase shift are not affected by the beam propagation obstruction effect,radar calibration,and propagation path attenuation.Therefore,it has a great advantage to corrected attenuated reflectivity according to the differential propagation phase shift and specific differential propagation phase shift.However,the estimation of the differential propagation phase shift and the specific differential propagation phase shift is easily affected by the variability of the meteorological environment and the attenuation of the polarization parameters,resulting in performance that corrected the rainfall reflectivity attenuation applying for differential propagation phase shift depreciation,The priori information is difficult to obtain that will lead to the ability to estimate specific differential propagation phase shift depreciation,besides in the case of low signal to noise ratio,it is difficult to retain the real meteorological information.In view of the above problems,the correction method of the reflectivity attenuation in the rainfall area proposed in this paper that can obtain good correction effect.The main work of the paper is:Firstly,the working principle and main performance parameters of the dual-polarization Doppler radar are introduced.The definition and physical meaning of each polarization parameter are analyzed,which provides the theoretical basis for the subsequent attenuation correction.Secondly,the data acquisition process of the dual-polarization meteorological radar is studied.The important factors that affected the polarization parameters of the radar are analyzed.The radial propagation is used to preprocess the differential propagation phase shift and improve reliability of the subsequent data analysis.Thirdly,a method of reflectivity attenuation based on Particle filter is proposed.Themethod is insensitive to process excitation noise,when a lack of the process excitation noise prior information,it still has a stable estimation result.The method can not only estimate the differential propagation phase shift accurately,improve the continuity,smoothness and accuracy of the filtered data,and improve the non-negativeity of the specific propagation phase shift,but also the corrected reflectivity based on Particle filter is closer to the true value.Fourthly,a method of reflectivity attenuation based on Kalman-Particle filter is proposed.When the noise prior information is known,The method can obtain high precision correction results,compared with proposed particle filter,the differential propagation phase shift and specific differential propagation phase shift based on Kalman-Particle filtering method conform to the real meteorological Environment,reflectivity after correction is more close to the true value,the estimation accuracy is higher.However,calculation amount is large.