NYTEFOX - The NY-Ålesund TurbulencE Fiber Optic eXperiment investigating the Arctic boundary layer, Svalbard

Atmospheric processes in the weak-wind stable boundary layer are an open field of research since they are poorly represented by theoretical concepts including similarity theories commonly applied in the air layer adjacent to the surface. This lack of understanding affects polar regions the most since the observation density is sparse while the fraction of weak-wind conditions with strong static stability increases drastically during polar night which is characterized by a long-lived stable boundary layer. The atmospheric motions carrying the bulk of the near-surface transport in these conditions occur on scales larger than forced or free convective turbulence, show different characteristics and are known as submeso-scale motions. These submeso-scale motions cannot be resolved by common point measurements due to their quasi-stationary or transient behavior but require distributed observations such as from sensor networks or continuous observational techniques. A suite of observations satisfying these requirements were collected during the Ny-Ålesund TurbulencE Fiber Optic eXperiment, NYTEFOX, which was a field campaign conducted at an Arctic field site at the perimeter of the Ny-Ålesund science station (11.9°E, 78.9°N) in February and March 2020. It was the first field campaign in an Arctic environment to investigate the spatio-temporal variability of airflow and temperature across hundreds of meters horizontally by means of the innovative Fiber-Optic Distributed Sensing (FODS) technique. A 700 m long horizontal, trapezoidal transect of fiber-optic cables installed at 1.2 m above ground level (agl) yielded measurements of temperature and wind speed with a resolution of 0.127 m and 9 s, supplemented by three 7 m tall vertical profiles. A coil-wrapped column of fiber-optic cable, helically wound around a support fabric, added a high-resolution vertical temperature profile from below the snow surface (-0.25 m) up to 2.5 m agl with an effective vertical resolution of 0.0025 m to 0.02 m depending on height. The 14-day FODS data set spanning the period from 26.02.2020 until 10.03.2020 is complemented by observations of three ultrasonic anemometers and one acoustic profiler (miniSodar, SOund Detection And Ranging) measuring a wind profile up to 300 m agl. The NYTEFOX data set allows for exploring the role, as well as the horizontal scales, vertical scales, and the trajectories, of turbulent and submeso-scale motions in the Arctic during the transition from the polar night to spring. The atmospheric observations from this pilot field campaign substantially expand the data set operationally collected by the Basic Surface Radiation Network (BSRN) meteorological data set at Ny-Ålesund, Svalbard by observing airflow and temperatures at turbulent to submeso scales. A technical documentation and file overview is given here (documentation_v1_1.pdf). A more detailed description of the setup and processing steps as well as an exemplary illustration of the observations on 05.03.2020 can be found in Zeller et al. (2021). All data are provided either as comma separated ASCII (csv, for the ultrasonic anemometer statistics) or as self-describing netcdfs. Only changes in Version v1.1: updated data availability in the documentation PDF. This project has received funding from the Alfred Wegener Institute for Polar and Marine Research (AWI) in Potsdam, the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant agreement No. 724629 DarkMix, PI: Christoph Thomas), and the Research Council of Norway (project number 291644) Svalbard Integrated Arctic Earth Observing System (SIOS) – Knowledge Centre, operational phase. The experiment was conducted with the support of the joint French-German AWIPEV-Station operated by the AWI and the Polar Institute Paul Emile Victor (IPEV) in Ny-Ålesund.弱风稳定边界层内的大气过程是当前尚未被充分研究的前沿领域，因为包括常用于近地表气层的相似性理论在内的各类理论概念，均难以准确表征这类过程。这种认知缺失对极地地区的影响尤为显著：极地夜间以长寿命稳定边界层为典型特征，此时强静力稳定的弱风工况占比大幅攀升，而极地的观测密度却相对稀疏。在此类工况下，主导近地表输运过程的大气运动，其尺度大于强迫对流或自由对流湍流，且具备独特的运动特征，这类运动被称为亚中尺度运动（submeso-scale motions）。由于这类亚中尺度运动具有准静止或瞬态特性，常规单点观测无法对其进行有效解析，需借助传感器网络或连续观测技术等分布式观测手段。满足上述观测需求的整套观测数据，采集自2020年2月至3月于新奥尔松科学站（11.9°E，78.9°N）周边北极野外站点实施的新奥尔松湍流光纤实验（Ny-Ålesund Turbulence Fiber Optic eXperiment, NYTEFOX）。该实验是北极环境中首个利用创新型光纤分布式传感（Fiber-Optic Distributed Sensing, FODS）技术，开展数百米水平范围内气流与温度时空变化研究的野外观测项目。实验中布设了一条长700米的水平梯形光纤线缆断面，安装于离地1.2米（agl，above ground level）高度处，可获取分辨率为0.127米（空间）与9秒（时间）的温度与风速观测数据，同时辅以3套7米高的垂直廓线观测系统。另有一卷缠绕于支撑织物上的螺旋光纤线缆，可获取从雪面以下0.25米至离地2.5米高度的高分辨率垂直温度廓线，其有效垂直分辨率随高度变化，范围为0.0025米至0.02米。这套时长14天的光纤分布式传感数据集的观测时段为2020年2月26日至3月10日，同时辅以3台超声风速仪与1台声学廓线仪（miniSodar，声检测与测距系统，SOund Detection And Ranging）的观测数据，后者可获取离地300米高度内的风速廓线。NYTEFOX数据集可用于研究北极地区从极夜向春季过渡期间，湍流运动与亚中尺度运动的作用机制、水平尺度、垂直尺度及其运动轨迹。本次先导野外实验获取的大气观测数据，填补了斯瓦尔巴群岛新奥尔松地区基础地表辐射网（Basic Surface Radiation Network, BSRN）气象数据集的观测空白，实现了从湍流尺度到亚中尺度的气流与温度观测，大幅扩充了该区域的现有观测数据集。本数据集的技术文档与文件概览可参见（documentation_v1_1.pdf）。关于实验布设方案、数据处理流程的详细说明，以及2020年3月5日的观测示例分析，可参阅Zeller等人2021年的研究成果。所有数据均以两种格式提供：逗号分隔的ASCII文本文件（comma separated ASCII，csv，适用于超声风速仪统计数据），以及自描述型netCDF格式文件。v1.1版本仅更新了文档PDF中的数据可用性说明内容。本项目获得了以下机构的资助：波茨坦极地与海洋研究阿尔弗雷德·魏格纳研究所（Alfred Wegener Institute for Polar and Marine Research, AWI）；欧盟“地平线2020”研究与创新框架下的欧洲研究理事会（European Research Council, ERC）资助项目（协议编号：724629 DarkMix，项目负责人：Christoph Thomas）；以及挪威研究理事会资助的斯瓦尔巴集成北极地球观测系统（Svalbard Integrated Arctic Earth Observing System, SIOS）知识中心运营阶段项目（项目编号：291644）。本次实验得到了由AWI与保罗·埃米尔·维克多极地研究所（Polar Institute Paul Emile Victor, IPEV）联合运营的法德联合AWIPEV站的支持。