毫米波测云雷达回波的衰减订正研究

Research of Millimeter-Wave Cloud Radar on Attenuation Correction

毫米波测云雷达探测云目标时,电磁波除了受到云目标衰减之外,还受到大气传输中氧气以及水汽的衰减,电磁波的衰减导致雷达观测到的回波强度小于云目标的实际回波强度,这种误差将影响云内结构的反演。因此,为了使毫米波测云雷达的探测数据正确地反演出云目标的宏观物理特征,必须对进行毫米波测云雷达工作频率下气象目标物的衰减进行订正。主要利用逐库衰减订正算法以及分级逐库衰减订正算法对英国Chilbolton观测场94 GHz毫米波测云雷达的一次降水云观测结果进行了垂直方向的大气衰减订正研究,并比较逐库衰减订正算法以及分级逐库衰减订正算法间的反演差异。同时,利用国际电信联盟ITU-RP.676-10建议书中氧气以及水汽衰减订正公式进行了毫米波测云雷达探测数据的二次订正。分析和对比结果表明,衰减系数的变化对于云目标的宏观物理特征反演有着明显的影响,并且分级逐库衰减订正法的订正效果强于逐库衰减订正法。

When millimeter-wave cloud radar detects cloud targets,electromagnetic wave not only suffer the attenuation of cloud targets,but also the attenuation of oxygen and water vapor in the atmosphere. Electromagnetic wave attenuation brings that the echo intensity data of radar observations is smaller than that of the actual cloud targets. This error will affect the cloud structure inversion. Thus,meteorological target attenuation correction must be carried out under the millimeter-wave cloud radar frequency in order to inverse exactly the macro physical characteristics of cloud targets by the detected datum of the millimeter-wave cloud radar. In this paper,we researched a precipitation clouds attenuation correction in vertical direction which detected by 3 mm cloud radar at British Chilbolton observation by bin-by-bin attenuation correction algorithm and hierarchical bin-by-bin attenuation correction algorithm and compared their difference. Meanwhile,we conducted the second correction of the millimeter-wave cloud radar detected data by using ITU-RP. 676-10 atmospheric oxygen and water vapor attenuation correction formula. The above analysis and comparison results showed that the change of the attenuation coefficient has a significant impact on the cloud targets macro physical characteristics inversion. The effect of hierarchical bin-by-bin attenuation correction is stronger than that of bin-by-bin attenuation correction.