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基于层次聚类算法的云雷达水凝物相态识别及应用研究

Hydrometeor Identification Method and Its Application Using a Hierarchical Agglomerative Clustering Algorithm based on Cloud Radar Observations

  • 摘要: 针对模糊逻辑方法识别水凝物相态主观性强、不确定性大的问题,提出了凝聚型层次聚类和模糊逻辑相结合的云雷达水凝物相态识别新方法。该方法基于Ka波段云雷达观测的多种参量(基本反射率ZH、径向速度VR、速度谱宽Sw、退偏比LDR)结合再分析的温度资料构成多维数据集,首先利用凝聚型层次聚类算法得到各类相态对应的物理量特征,在此基础上采用模糊逻辑方法识别云系水凝物相态的垂直分布,结合机载微物理探测的云粒子图像进一步验证识别结果的可靠性。将该方法应用于华中地区春季混合云和东北地区秋季层状云系,结果显示识别的云系负温区冰晶、雪、混合相的垂直分布与云系垂直发展、回波宏微观特征演变较一致,其所在的高度层与机载探测结果具有较高的一致性,优于模糊逻辑和K均值聚类—模糊逻辑方法识别的水凝物分布,更符合云系发展降水形成的物理规律。

     

    Abstract: To overcome the subjectivity and uncertainty inherent in hydrometeor identification based on fuzzy logic, this study proposes a novel identification method that integrates hierarchical agglomerative clustering (HAC) with fuzzy logic, tailored for Ka-band cloud radar observations. This method utilizes multiple radar-derived parameters—reflectivity (ZH), radial velocity (VR), spectral width (Sw), and linear depolarization ratio (LDR)—along with temperature from reanalyzed data to construct a multidimensional dataset. The hierarchical agglomerative clustering algorithm is first applied to classify hydrometeor phases and extract their physical characteristics. Based on these clustering results, the fuzzy logic method is used to identify the vertical distribution of hydrometeor phases within cloud systems. The classification reliability is then verified using two-dimensional cloud particle images obtained from airborne microphysical probes. The proposed method was applied to spring mixed-phase clouds in Central China and autumn stratiform clouds in Northeast China. The identified vertical distributions of ice crystals, snow, and mixed-phase hydrometeors in the negative temperature region were consistent with the observed evolution of macro- and microphysical cloud characteristics. The estimated heights of each hydrometeor phase agreed well with in situ airborne measurements, outperforming both the traditional fuzzy logic and the K-means clustering–fuzzy logic methods, and aligned with the physical laws of cloud development and precipitation formation.

     

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