On the Projection of Polarimetric Variables Observed by a Planar Phased-Array Radar at X-Band
On the Projection of Polarimetric Variables Observed by a Planar Phased-Array Radar at X-Band
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DOI：
10.1109/tgrs.2020.3023640
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发表时间：
2020-09
影响因子：
8.2
通讯作者：
William Heberling;S. Frasier
中科院分区：
文献类型：
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作者：
William Heberling;S. Frasier
给出了X波段平面相控阵雷达(PPAR)观测到的双极化天气雷达变量的特征。这些特性由阵列辐射的偏振向定义地面天气雷达测量几何的标准球面坐标的投影来控制。辐射单元的方向相关的增益和相位、辐射极化的方向以及阵列的机械倾斜都是导致投影的原因，与使用反射面天线的机械扫描天气雷达相比，这导致了观测的偏差。我们将投影分解成可以针对各种PPAR配置进行分离和定制的组件，包括考虑单元可能的交叉极化辐射以及覆盖阵面的湿式雷达罩的影响。它们由乘积构成总投影的矩阵表示。我们将这种方法应用于X波段PPAR，使用降水量的就地测量来获得辐射模式的属性。然后，我们得到了常见天气雷达偏振变量的结果偏差。我们表明，偏差可以表示为本征变量与投影和目标相关的修正的乘积。依赖于投影的校正仅依赖于投影矩阵的元素，而依赖于目标的校正还依赖于固有的微分反射率和共轴或跨极相关系数。我们发现，依赖于投影的校正足以在大部分扫描范围内实现可接受的偏差。
We present the characteristics of dual-polarized weather radar variables as observed by a planar phased-array radar (PPAR) operating at X-band. The characteristics are governed by the projection of the polarizations radiated by the array into the canonical spherical coordinates defining the measurement geometry of ground-based weather radars. The direction-dependent gain and phase of the radiating elements, the orientation of the radiated polarizations, and the mechanical tilting of the array all contribute to the projection, which results in biased observations compared with those of a mechanically scanned weather radar employing a reflector antenna. We decompose the projection into components that can be separated and customized for various PPAR configurations, including consideration of possible cross-polarized radiation by the elements and the effect of a wet radome covering the array face. These are represented by matrices whose product comprises the total projection. We apply this methodology to an X-band PPAR using in-place measurements of precipitation to obtain the properties of the radiation pattern. We then obtain the resulting biases of common weather radar polarimetric variables. We show that the biases can be represented as a product of the intrinsic variables with projection- and target-dependent corrections. The projection-dependent corrections depend only upon elements of the projection matrix, while the target-dependent corrections also depend upon the intrinsic differential reflectivity and copolar or cross-polar correlation coefficients. We find that the projection-dependent corrections are sufficient to achieve acceptable bias over most of the scan range.