Weather radar systems have become a central tool in the study of nocturnal bird migration. Yet, while studies have sought to validate weather radar data through comparison to other sampling techniques, few have explicitly examined the impact of range and topographical blockage on sampling detection—critical dimensions that can bias broader inferences. Here, we assess these biases with relation to the Cheyenne, WY Next Generation Weather Radar (NEXRAD) site, one of the large‐scale radars in a network of 160 weather surveillance stations based in the United States. We compared local density measures collected using a mobile, vertically looking radar with reflectivity from the NEXRAD station in the corresponding area. Both mean nightly migration activity and within night migration activity between NEXRAD and the mobile radar were strongly correlated (r = 0.85 and 0.70, respectively), but this relationship degraded with both increasing distance and beam blockage. Range‐corrected NEXRAD reflectivity was a stronger predictor of observed mobile radar densities than uncorrected reflectivity at the mean nightly scale, suggesting that current range correction methods are somewhat effective at correcting for this bias. At the within night temporal scale, corrected and uncorrected reflectivity models performed similarly up to 65 km, but beyond this distance, uncorrected reflectivity became a stronger predictor than range‐corrected reflectivity, suggesting range limitations to these corrections. Together, our findings further validate weather radar as an ornithological tool, but also highlight and quantify potential sampling biases.

中文翻译：

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量化候鸟活动天气监测雷达测量的范围和地形偏差


气象雷达系统已成为研究夜间鸟类迁徙的核心工具。然而，虽然研究试图通过与其他采样技术进行比较来验证天气雷达数据，但很少有人明确研究范围和地形阻塞对采样检测的影响——这些关键维度可能会使更广泛的推断产生偏差。在这里，我们评估了与怀俄明州夏延下一代天气雷达 （NEXRAD） 站点相关的这些偏差，该站点是由美国 160 个天气监测站组成的网络中的大型雷达之一。我们将使用移动垂直雷达收集的局部密度测量值与相应区域 NEXRAD 站的反射率进行了比较。NEXRAD 和移动雷达之间的平均夜间迁移活动和夜间迁移活动均具有很强的相关性（分别为 r = 0.85 和 0.70），但这种关系随着距离的增加和波束遮挡而降低。在平均夜间尺度上，距离校正的 NEXRAD 反射率比未校正的反射率更能预测观察到的移动雷达密度，这表明当前的距离校正方法在校正这种偏差方面有些有效。在夜间时间尺度上，校正和未校正的反射率模型在 65 公里内的表现相似，但在此距离之外，未校正的反射率成为比范围校正反射率更强的预测因子，这表明这些校正的范围有限。总之，我们的研究结果进一步验证了天气雷达作为一种鸟类学工具，但也突出并量化了潜在的采样偏差。