多普勒天气雷达地物回波预测及折射率剖面反演研究

According to the weather radar equation, a method that can calculate ground returns using atmospheric refractivity profiles as input will be studied, which is based on the parabolic equation method used widely in radiowave propagation under tropospheric ducting conditions and the technique of ray tracing and land/sea clutter model. And the model of predicting the strength of ground returns of Doppler weather radar is intended to be founded. As a forward model, the ground return predict model combines optimizational algorithm to explore the technique of retrieving the lower atmopheric refractivity profiles, which make use of the ground returns. Doppler weather radar observation experiments are planned to contact within the littoral environment and to collect radiosonde data. Three-dimensional refractivity profiles around the weather radar are derived from mesoscale numerical weather prediction. Through comparisons between simulated and radar observation results, the model of predicting ground returns will be validated and completed. The technique of retrieving refractivity profile using ground returns will be tested by the experimental data. The subject study could provide basic theoretical and technical support for explaining the mechanism of the generation and influence of super-refractive ground returns or anomalous propagation (AP), and for identifying and rejecting ground returns, as well as the exploitation of ground returns. The research has important meaning for quality control of the Doppler weather radar data.

基于对流层大气波导传播的抛物方程方法，并采用射线描迹技术、地海杂波模型，利用雷达气象方程，研究根据大气折射率环境计算雷达地物回波的方法，建立多普勒雷达地物回波强度的预测模型。以建立的地物回波预测为正演模型，结合优化反演算法，进一步研究利用地物回波获得低空大气折射率剖面的反演方法和模型。在沿海开展多普勒天气雷达观测实验，收集气象探空数据，用中尺度数值天气预报模式获得雷达周边三维折射率数据，比较模型预测和雷达实际观测结果，验证完善地物回波预测模型，检验地物回波反演大气折射率剖面的性能。课题研究对阐明超折射等反常地物回波产生和影响机制、识别和抑制地物回波，以及地物回波的有效利用提供基础理论与技术支撑，对多普勒天气雷达观测数据质量控制有重要意义。

反常传播引起的地物回波是影响新一代天气雷达数据质量重要因素。基于对流层大气波导传播的抛物方程方法，并采用射线描迹技术、地海杂波模型，利用雷达气象方程，根据大气折射率环境计算雷达地物回波的方法，建立多普勒雷达地物回波强度的预测模型。以建立的地物回波预测为正演模型，结合优化反演算法，进一步获得利用地物回波获得低空大气折射率剖面的反演方法和模型。根据青岛气象局多普勒天气雷达回波图分析了电波传播随时间和空间的变化特性，并分析了不同仰角情况下多普勒天气雷达回波的分布特征，进一步验证了大气波导环境对电波传播的影响。利用主分量分析方法构建水平非均匀大气波导修正折射率剖面参数模型，然后使用粒子群优化算法对剖面参数进行采样，最后根据反演模型获得大气修正折射率剖面。 利用马尔科夫链蒙特卡洛采样算法对剖面参数快速采样，基于贝叶斯后验概率估计理论计算得到反演剖面参数的后验概率密度分布，得到了反演剖面的情况下分析反演结果的不确定性。最后将中尺度WRF模式模拟的大气修正折射率作为先验信息对反演结果进行修正，结果表明贝叶斯反演方法反演结果比较准确，含先验信息时反演结果的确定性增强。课题研究对阐明超折射等反常地物回波产生和影响机制、识别和抑制地物回波，以及地物回波的有效利用提供基础理论与技术支撑，对多普勒天气雷达观测数据质量控制有重要意义。