双线偏振雷达资料在数值模式中的应用: 模拟器的构建

Application of the dual-polarization radar data in numerical modeling studies: Construction of the simulator

  • 摘要: 基于Rayleigh-Gans散射原理构造一个S波段双线偏振雷达模拟器。模拟器考虑了云冰、雪、雨和雹4种水凝物,以水凝物的混合比和数浓度以及水凝物粒子的轴比、相对介电常数、下落倾角为输入量,计算得到水平/垂直偏振反射率因子、差分反射率、比差分相位等偏振量。通过二维理想飑线模拟的试验结果表明,模拟器合理地再现了二维理想飑线系统成熟期的主要偏振特征:雹的反射率较高,差分反射率较低(又称Zdr洞);对流云区的Zdr柱;层云区的反射率和比差分相位的0℃层亮带特征;雨滴反射率与差分反射率因子的“雨线”统计特征。利用该模拟器建立了模式变量和偏振雷达观测的联系,有助于未来将偏振雷达观测资料应用于模式预报效果评估及对流尺度资料同化等方面的研究和应用。

     

    Abstract: Based on the Rayleigh-Gans scattering theory,a simulator for S-band dual-linear polarization radar with the wavelength of 10 cm has been developed. The simulator considers four hydrometeors (i.e., cloud ice, snow, rain, hail), takingcloud mixing ratios and number concentrations from microphysics scheme and the axis ratio, relative dielectric constant and canting angles of particles as input, and then calculating reflectivity at horizontal and vertical polarizations, differential reflectivity, specific differential phase and others. Realistic polarimetric radar signatures of a mature 2D ideal squall-line are well produced in the simulation: Hail has high horizontal reflectivity and low differential reflectivity (Zdr hole);Zdr column in convective regions is well simulated; bright bands of horizontal reflectivity and specific differential phase show clearly in the results;and the linear relationship between the horizontal reflectivity and differential reflectivity factor of rain (rain line) is well represented. The simulator builds a direct link between model variables and polarization radar observations. In the near future, it will be used as a tool to evaluate the effect of model predictions and to directly as similate polarimetric variables into convection-resolved model.

     

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