Polarimetric Radar Variables in Snowfall at Ka- and W-Band Frequency Bands: A Comparative Analysis
Polarimetric Radar Variables in Snowfall at Ka- and W-Band Frequency Bands: A Comparative Analysis
复制标题
Ka 和 W 频段降雪中的偏振雷达变量：比较分析
DOI：
10.1175/jtech-d-20-0138.1
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发表时间：
2021
影响因子：
2.2
通讯作者：
Matrosov, Sergey Y.
中科院分区：
文献类型：
--
作者：
Matrosov, Sergey Y.
双频毫米波雷达观测降雪进行了分析，以评估传统的偏振雷达变量，如微分反射率（ZDR）的差异，具体的微分相移（KDP）和线性去偏振比（LDR）在传统的云雷达频率在Ka和W波段（~35和~94 GHz，相应地）。低雷达波束仰角（~5°）测量是在阿拉斯加的奥利克托克角进行的，使用的是一台扫描全极化雷达，以水平-垂直极化方式工作。该雷达在两个频率上具有相同的门间距和非常接近的波束宽度，这在很大程度上消除了与空间和时间数据匹配相关的不确定性。结果表明，所观察到的Ka-和W-波段ZDR的差异，平均而言，小于约0.5分贝，并没有一个明显的趋势作为降雪反射率的函数。的advervedZDR差异同意以及使用积分非球形冰颗粒尺寸分布的模拟结果。对于更高的信号-噪声比，KDP数据来自差分相位测量近似缩放为相应的雷达频率的倒数，这表明非瑞利散射效应对这个变量的影响是相当有限的。这一结果也是令人满意的协议，通过使用现实的粒度分布建模获得的数据。观测到的Ka波段和W波段LDR差异受到雷达硬件系统极化“泄漏”的强烈影响，并且通常小于4 dB。对于较高的去极化，观察到较小的差异，其中极化“泄漏”不太明显。粒子倾斜和系统的极化隔离的现实假设，导致令人满意地同意与观测双频LDR数据的建模结果。
Dual-frequency millimeter-wavelength radar observations in snowfall are analyzed in order to evaluate differences in conventional polarimetric radar variables such as differential reflectivity (ZDR) specific differential phase shift (KDP) and linear depolarization ratio (LDR) at traditional cloud radar frequencies at Ka and W bands (~35 and ~94 GHz, correspondingly). Low radar beam elevation (~5°) measurements were performed at Oliktok Point, Alaska, with a scanning fully polarimetric radar operating in the horizontal–vertical polarization basis. This radar has the same gate spacing and very close beam widths at both frequencies, which largely alleviates uncertainties associated with spatial and temporal data matching. It is shown that observed Ka- and W-bandZDRdifferences are, on average, less than about 0.5 dB and do not have a pronounced trend as a function of snowfall reflectivity. The observedZDRdifferences agree well with modeling results obtained using integration over nonspherical ice particle size distributions. For higher signal-to-noise ratios,KDPdata derived from differential phase measurements are approximately scaled as reciprocals of corresponding radar frequencies indicating that the influence of non-Rayleigh scattering effects on this variable is rather limited. This result is also in satisfactory agreement with data obtained by modeling using realistic particle size distributions. Observed Ka- and W-band LDR differences are strongly affected by the radar hardware system polarization “leak” and are generally less than 4 dB. Smaller differences are observed for higher depolarizations, where the polarization “leak” is less pronounced. Realistic assumptions about particle canting and the system polarization isolation lead to modeling results that satisfactorily agree with observational dual-frequency LDR data.