Abstract With the advent of the Global Precipitation Measurement (GPM) mission and the associated Ground Validation campaigns, there has been a strong development of studies related to dual-frequency and more recently to triple-frequency radar. In this context, one requirement is that at least one of the radar frequencies operates in the Rayleigh regime while the others have to ensure a measurable difference in reflectivities. A common radar coupling for triple frequency systems is the Ku-, Ka-, and W-band. Multi-frequency radars, in addition to the classic single-frequency reflectivity (SFR) measurement for each frequency, allow a further parameter, the dual-frequency ratio (DFR) defined as the ratio between two reflectivities at two frequencies. Referring to the same measurement volume, and for a fixed microphysical ice particle model, SFR and DFR allow to better constraint parameters of the particle size distribution, such as the mass-weighted mean diameter (Dm) and the normalized intercept parameter (Nw) when a normalized gamma distribution is assumed. This paper deals with various topics with the preliminary purpose of assessing the accuracy of the ice water content (IWC) estimate obtained using SFR and DFR methods to evaluate the improvements brought by the use of DFR. To pursue this goal, a simple microphysical model was used to choose the form of the SFR and DFR estimation algorithms and to evaluate their performances in a simulated framework. The most important aspect revealed by the study is that the cloud water content (CWC) plays a very important role both in the mass vs. diameter relationship as well as in the IWC estimation. The combined use of specific radar algorithms according to the different CWC values has shown notable improvements for the IWC estimation. Since CWC is not an operational measure, a substitute parameter was sought in the (DFRaou, DFRwoa) domain defined by the Ka- and Ku-band and by the W- and Ka-band measurements. This new parameter provides improvements similar to those obtained with the use of CWC. Data from the OLYMPEX field campaign that include an airborne triple-frequency radar at Ku-, Ka-, and W-band, as well as airborne measurements of in-situ bulk microphysics and meteorological parameters were used to validate the robustness of the methodology.

中文翻译：

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单频、双频和三频雷达场景中的冰水含量评估

摘要 随着全球降水测量 (GPM) 任务和相关地面验证活动的出现，与双频和最近三频雷达相关的研究取得了长足的发展。在这种情况下，一个要求是至少一个雷达频率在瑞利范围内运行，而其他频率必须确保反射率存在可测量的差异。三频系统的常见雷达耦合是 Ku、Ka 和 W 波段。多频雷达除了对每个频率进行经典的单频反射率 (SFR) 测量外，还允许使用另一个参数，即双频比 (DFR)，定义为两个频率下的两个反射率之间的比率。参照相同的测量体积，对于固定的微物理冰粒模型，当假定归一化伽马分布时，SFR 和 DFR 允许更好地约束粒度分布的参数，例如质量加权平均直径 (Dm) 和归一化截距参数 (Nw)。本文涉及各种主题，初步目的是评估使用 SFR 和 DFR 方法获得的冰水含量 (IWC) 估计的准确性，以评估使用 DFR 带来的改进。为了实现这一目标，使用一个简单的微物理模型来选择 SFR 和 DFR 估计算法的形式，并在模拟框架中评估它们的性能。该研究揭示的最重要的方面是云水含量 (CWC) 在质量与直径的关系以及 IWC 估计中都起着非常重要的作用。根据不同的 CWC 值结合使用特定的雷达算法，已显示出对 IWC 估计的显着改进。由于 CWC 不是一种操作测量，因此在由 Ka 和 Ku 波段以及 W 和 Ka 波段测量定义的（DFRaou，DFRwoa）域中寻找替代参数。这个新参数提供的改进类似于使用 CWC 获得的改进。来自 OLYMPEX 野外活动的数据，包括 Ku 波段、Ka 波段和 W 波段的机载三频雷达，以及原位体微物理和气象参数的机载测量，用于验证该方法的稳健性。DFRwoa) 域由 Ka 和 Ku 波段以及 W 和 Ka 波段测量定义。这个新参数提供的改进类似于使用 CWC 获得的改进。来自 OLYMPEX 野外活动的数据，包括 Ku 波段、Ka 波段和 W 波段的机载三频雷达，以及原位体微物理和气象参数的机载测量，用于验证该方法的稳健性。DFRwoa) 域由 Ka 和 Ku 波段以及 W 和 Ka 波段测量定义。这个新参数提供的改进类似于使用 CWC 获得的改进。来自 OLYMPEX 野外活动的数据，包括 Ku 波段、Ka 波段和 W 波段的机载三频雷达，以及原位体微物理和气象参数的机载测量，用于验证该方法的稳健性。