Monitoring the evolution of snow on the ground and lake ice—two of the most important components of the changing northern environment—is essential. In this paper, we describe a lightweight, compact and autonomous 24 GHz frequency-modulated continuous-wave (FMCW) radar system for freshwater ice thickness and snow mass (snow water equivalent, SWE) measurements. Although FMCW radars have a long-established history, the novelty of this research lies in that we take advantage the availability of a new generation of low cost and low power requirement units that facilitates the monitoring of snow and ice at remote locations. Test performance (accuracy and limitations) is presented for five different applications, all using an automatic operating mode with improved signal processing: (1) In situ lake ice thickness measurements giving 2 cm accuracy up to ≈1 m ice thickness and a radar resolution of 4 cm; (2) remotely piloted aircraft-based lake ice thickness from low-altitude flight at 5 m; (3) in situ dry SWE measurements based on known snow depth, giving 13% accuracy (RMSE 20%) over boreal forest, subarctic taiga and Arctic tundra, with a measurement capability of up to 3 m in snowpack thickness; (4) continuous monitoring of surface snow density under particular Antarctic conditions; (5) continuous SWE monitoring through the winter with a synchronized and collocated snow depth sensor (ultrasonic or LiDAR sensor), giving 13.5% bias and 25 mm root mean square difference (RMSD) (10%) for dry snow. The need for detection processing for wet snow, which strongly absorbs radar signals, is discussed. An appendix provides 24 GHz simulated effective refractive index and penetration depth as a function of a wide range of density, temperature and wetness for ice and snow.

中文翻译：

---

低成本和紧凑型FMCW 24 GHz雷达应用，用于雪堆和冰厚测量。

监测不断变化的北方环境中最重要的两个组成部分-地上冰雪和湖冰的演变至关重要。在本文中，我们描述了一种轻型，紧凑且自主的24 GHz调频连续波（FMCW）雷达系统，用于测量淡水冰层厚度和积雪量（雪水当量，SWE）。尽管FMCW雷达已有很长的历史，但这项研究的新颖之处在于，我们利用了新一代低成本和低功率需求单元的优势，该单元有助于远程监测冰雪。介绍了针对五种不同应用的测试性能（准确性和局限性），所有这些应用均使用具有改进的信号处理能力的自动操作模式：（1）原位湖冰厚测量，在2mm的精度范围内可达到≈1m冰厚，雷达分辨率为4 cm；（2）在5 m处低空飞行的遥控飞机冰湖厚度；（3）基于已知积雪深度的原位干燥SWE测量，在北方森林，北极针叶林和北极苔原上的准确度为13％（RMSE 20％），积雪厚度的测量能力高达3 m；（4）在特定南极条件下连续监测地表雪密度；（5）使用同步并置的积雪深度传感器（超声波或LiDAR传感器）在整个冬季进行连续SWE监测，得出干雪的13.5％偏差和25 mm的均方根差（RMSD）（10％）。讨论了对强烈吸收雷达信号的湿雪的检测处理的需求。