基于差分传播相移的Dual-Pol雷达衰减订正方法研究

发布时间：2018-05-09 05:20

本文选题：双偏振雷达 + 衰减订正　；参考：《中国民航大学》2017年硕士论文

【摘要】：气象雷达是探测气象环境的重要手段,广泛应用于减灾和灾害预警,它根据回波的变化来评估气象目标的特性,当路径上存在降雨区时,会造成反射率的衰减,无法准确的估计探测目标的气象特征,也可能淹没后方降雨区。对于频率较低的X波段,这种衰减更加严重,为了准确分析气象目标的真实特性,提高降水估测的精度,需要对反射率进行衰减订正。双偏振多普勒雷达相比于常规雷达,能够提供表征粒子微物理特性的差分传播相移,差分传播相移与降雨率之间不仅具有比较高的相关性,而且还具有不受波束传播阻碍效应、雷达校准、传播路径衰减影响的特性,因此使用差分传播相移进行反射率的衰减订正有很大的优势。然而差分传播相移与差分传播相移率的估计效果容易受到多变性的气象环境和衰减的偏振参量的影响,导致使用差分传播相移与对降雨区的反射率进行衰减订正的性能降低,先验信息难以获取也会导致差分传播相移率的估计能力下降,并且在低信噪比的情况下难以保留真实的气象信息。针对上述问题,本论文提出的降雨区反射率衰减订正方法能够获得较好的订正效果。论文的主要工作为:第一,介绍了双偏振多普勒雷达的工作原理以及主要的性能参数,分析了各偏振参量的定义与物理意义,为后续对反射率进行衰减订正提供理论依据。第二,研究了双偏振气象雷达的数据获取过程,分析了影响雷达偏振参量的主要因素,采用径向连续性对差分传播相移进行了预处理,为后续数据分析提高可靠性。第三,提出了一种基于粒子滤波的反射率衰减订正方法,该方法对激励噪声不敏感,在激励噪声先验信息未知的情况下,仍然具有稳定的估计结果,不仅可以准确估计差分传播相移,使滤波处理后的数据具有更好的连续性、平滑性和准确性,改善了差分传播相移率的非负性,而且粒子滤波处理后订正的反射率比较接近真值。第四,提出了基于Kalman-Particle滤波的反射率的高精度衰减订正方法,当激励噪声的先验信息已知时,该方法能够获得精度较高的订正结果,与所提的粒子滤波方法相比,经过Kalman-Particle滤波方法处理的差分传播相移与差分传播相移率更加符合真实气象环境,衰减订正后的反射率更加接近真值,估计精度更高。但是运算量相对较大。
[Abstract]:Meteorological radar is an important means to detect meteorological environment, which is widely used in disaster mitigation and early warning. It evaluates the characteristics of meteorological target according to the change of echo, and it will cause the attenuation of reflectivity when there is a raindrop area on the path. The weather characteristics of the target can not be estimated accurately, and the downfall area may also be inundated. In order to accurately analyze the real characteristics of meteorological targets and improve the accuracy of precipitation estimation, the attenuation correction of reflectivity is needed for the X band with lower frequency. Compared with conventional radar, dual-polarization Doppler radar can provide differential propagation phase shift, which can represent the microphysical properties of particles. The phase shift of differential propagation and rainfall rate are not only highly correlated, but also have the effect of not being hindered by beam propagation. Radar calibration, propagation path attenuation effect, so using differential propagation phase shift for reflectivity attenuation correction has a great advantage. However, the estimation effect of differential propagation phase shift and differential propagation phase shift rate is easily affected by the variable meteorological environment and attenuation polarization parameters, which results in a decrease in the performance of using differential propagation phase shift and attenuation correction of reflectivity in rain area. The difficulty of obtaining prior information also leads to the decrease of the estimation ability of differential propagation phase shift rate, and it is difficult to retain the true meteorological information in the case of low signal-to-noise ratio (SNR). In order to solve the above problems, the correction method of reflectance attenuation in raindrop area proposed in this paper can get a better effect. The main work of this paper is as follows: first, the working principle and main performance parameters of dual-polarization Doppler radar are introduced, and the definition and physical significance of each polarization parameter are analyzed, which provides a theoretical basis for the subsequent correction of reflectivity attenuation. Secondly, the data acquisition process of dual-polarization weather radar is studied, and the main factors affecting the radar polarization parameters are analyzed. The differential propagation phase shift is preprocessed by radial continuity, which improves the reliability of the subsequent data analysis. Thirdly, a reflectivity attenuation correction method based on particle filter is proposed. This method is insensitive to excitation noise, and still has stable estimation results when the priori information of excitation noise is unknown. Not only can the phase shift of differential propagation be estimated accurately, but also the data processed by filter have better continuity, smoothness and accuracy, and the non-negativity of differential propagation phase shift rate can be improved. And the corrected reflectivity of particle filter is close to the true value. Fourthly, a high precision attenuation correction method based on Kalman-Particle filter is proposed. When the priori information of excitation noise is known, the proposed method can obtain higher accuracy correction results, compared with the proposed particle filter method. The differential propagation phase shift and differential propagation phase shift rate processed by the Kalman-Particle filtering method are more in line with the real meteorological environment. The attenuated revised reflectivity is closer to the true value and the estimation accuracy is higher. But the computation is relatively large.
【学位授予单位】：中国民航大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN958

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