Spatio-temporally continuous temperature monitoring using optical fibers (Loop1) in the internal forest areas at Alaska in 2017

A fibre-optic DTS (distributed temperature sensing) system using Raman-scattering optical time domain reflectometry was deployed to monitor a boreal forest research site in the interior of Alaska. Surface temperatures range between -40 C in winter and 30 C in summer at this site. In parallel experiments, a fibre-optic cable sensor system (multi-mode, GI50/125, dual core; 3.4 mm), monitored at high resolution, (0.5m intervals at every 30 min) ground surface temperatures across the landscape. In addition, a highresolution vertical profile was acquired at one-metre height above the upper subsurface. The total cable ran 2.7 km with about 2.0 km monitoring a horizontal surface path. Sections of the cable sensor were deployed in vertical coil configurations (1.2m high) to measure temperature profiles from the ground up at 5mm intervals. Measurements were made continuously over a 2-year interval from October 2012 to October 2014. Vegetation at the site (Poker Flat Research Range) consists primarily of black spruce underlain by permafrost. Land cover types within the study area were classified into six descriptive categories: relict thermokarst lake, open moss, shrub, deciduous forest, sparse conifer forest, and dense conifer forest. The horizontal temperature data exhibited spatial and temporal changes within the observed diurnal and seasonal variations. Differences in snow pack evolution and insulation effects co-varied with the land cover types. The apparatus used to monitor vertical temperature profiles generated high-resolution (ca. 5 mm) data for air column, snow cover, and ground surface.本研究部署了一套基于拉曼散射光时域反射（Raman-scattering optical time domain reflectometry）技术的光纤分布式温度传感（distributed temperature sensing, DTS）系统，用于对阿拉斯加内陆的寒温带森林研究站点开展温度监测。该站点地表温度冬季最低可达-40℃，夏季最高达30℃。 在并行对照实验中，一套多模GI50/125双芯光纤光缆传感器系统（外径3.4mm）被用于研究区全域地表温度的高分辨率监测，采样间隔为0.5m，每30分钟完成一次数据采集。此外，研究人员还在地表上方1米高度处获取了高分辨率垂直温度剖面数据。该光缆总长度为2.7km，其中约2.0km用于布设水平地表监测路径。部分光缆传感器采用垂直线圈构型（线圈高度1.2m），以5mm的采样间隔采集从地表向上的温度剖面数据。本次监测于2012年10月至2014年10月间连续开展，历时共计2年。 该站点（扑克弗拉特研究靶场，Poker Flat Research Range）的植被以黑云杉为主，林下发育多年冻土。研究区内的土地覆盖类型可划分为6类：残余热喀斯特湖、开放苔藓地、灌丛、落叶林、稀疏针叶林以及茂密针叶林。 水平温度监测数据呈现出观测周期内昼夜与季节尺度的时空动态变化特征。积雪演化过程与保温效应的差异与土地覆盖类型呈现显著的协同变化关系。 用于垂直温度剖面监测的设备可获取空气柱、积雪层以及地表的高分辨率（约5mm）监测数据。