针对S波段双线偏振天气雷达，提出了一种基于水平反射率因子Zh、线性退偏比LDR和差分反射率因子Zdr等探测量的图像合成技术，根据它们各自的探测范围将3个变量线性调整至0~255的范围，再在RGB色彩空间内分别赋予图像的三个通道，从而得到全新的伪彩合成图像，对比分析发现，分别采用LDR、Zh、Zdr作为RGB分量的组合方式得到的合成图像能够体现出更为丰富的信息，新的图像保留了原始反射率因子的结构特征，两个偏振探测量特征也能通过色彩的差异而体现，同时具有较为舒适的视觉特征。根据不同类型水凝物粒子的取值范围，分别计算了不同类型粒子在LDR-Zh-Zdr合成图中的颜色值，定性分析表明不同类型粒子对应的颜色值有较大的差异，有利于人眼直接鉴别。用雷达PPI和RHI扫描数据进行个例分析表明，利用LDR、Zh、Zdr作为RGB分量方法得到的合成图像保持了原有反射率因子结构特征，图像不同色彩对应的粒子相态分布合理，用该图像能够方便地对雷达回波类型进行合理判断。
Pseudo-color composite technique has widely used in satellite remote sensing applications. Polarimetric radar can give more measurements that make the use of color composite technique in radar possible. Based on three S-band polarimetric radar measurements (reflectivity factor Zh, differential reflectivity factor Zdr and linear depolarization radio LDR), a method for color composite is given. According their respective measure range, Zh, Zdr and LDR are scaled to 0~255 linearly as the RGB channel data to form RGB image. Comparing shows that within all the combinations, the image formed by LDR, Zh and Zdr as R, G, B channel respectively can take on more abundant information, which not only retains the reflectivity structure characters, but also implicates the properties of the polarimetric measurements from different colors, and has more comfortable visual effect. For different type of hydrometeors, composite color is calculated according to their radar measurements range, and the qualitative analysis show that there is distinct difference between each two colors of given hydrometeors type, which favors the visual distinguishing. Case studies based on RHI and PPI data show that reflectivity structures are retained in the composite image, and the distribution of hydrometeor types implicated form colors is reasonable. The types of radar echoes can be easily estimated from this composite image, and the proposed color composite technique can be used in polarimetric radar operational applications.
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