Wind speed from actively heated fiber optic cables

Near-surface wind speed is typically only measured by point observations. The so-called Actively Heated Fiber-Optic (AHFO) technique, however, has the potential to provide high-resolution distributed observations, allowing for better understanding of different processes. However, before it can be widely used, its performance needs to be tested in a range of settings. Therefore, in this work, experimental results on this novel observational wind-probing technique are presented. We utilized a controlled wind-tunnel setup to assess both the accuracy and the precision of AHFO as well as its potential for outdoor atmospheric operation. The technique allows for wind speed characterization with a spatial resolution of 0.3 m on a 1 s time scale. The flow in the wind tunnel is varied in a controlled manner, such that the mean wind, ranges between 1 and 17 m/s. Comparison of the AHFO measurements with observations from a sonic anemometer shows a high overall correlation, ranging from 0.94-0.99. Also, both precision and accuracy are greater than 95 %. As such, it is concluded that the AHFO has potential to be employed as an outdoor observational technique in addition to existing techniques. In particular, it allows for characterization of spatial varying fields of mean wind in complex terrain, such as in canopy flows or in sloping terrain. In the future the technique could be combined with regular Distributed Temperature Sensing (DTS) for turbulent heat flux estimation in micrometeorological/hydrological applications. Raw DTS project data will be available in 2020 by contacting [e-mail].近地表风速通常仅通过单点观测手段获取。然而，主动加热光纤（Actively Heated Fiber-Optic, AHFO）技术具备提供高分辨率分布式观测的潜力，可助力研究者更深入地理解各类相关物理过程。但在实现广泛应用前，需在多种环境中对其性能开展验证。因此，本研究呈现了这一新型风速探测技术的实验结果。我们采用可控风洞实验装置，对AHFO技术的准确度、精度以及其在户外大气环境中的应用潜力进行了评估。该技术可实现0.3米空间分辨率、1秒时间尺度的风速表征。风洞内的气流以可控方式调节，平均风速区间为1至17 m/s。将AHFO的测量结果与超声风速仪的观测数据进行对比后发现，二者整体相关性极高，相关系数介于0.94至0.99之间。同时，其精度与准确度均超过95%。由此可见，AHFO技术具备作为现有观测手段之外的户外观测技术的应用潜力。具体而言，该技术可对复杂地形（如冠层流或坡地地形）中的平均风速空间变化场进行表征。未来，该技术可与常规分布式温度传感（Distributed Temperature Sensing, DTS）技术相结合，用于微气象/水文应用场景中的湍流热通量估算。 原始DTS项目数据将于2020年开放，可通过联系[e-mail]获取。