Spatio-temporally continuous temperature monitoring using optical fibers (Loop1) in the internal forest areas at Alaska in 2019

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仪的光纤分布式温度传感（distributed temperature sensing, DTS）系统，用于监测阿拉斯加内陆一处北方针叶林研究站点。该站点地表温度冬季介于-40℃至夏季30℃之间。 在平行对照实验中，一套高分辨率光缆传感器系统（多模、GI50/125型、双芯，外径3.4mm）以每30分钟一次的采样频率、0.5m的空间间隔，对研究区全域地表温度进行监测。此外，研究人员在地表上方1米高度处获取了高分辨率垂直温度剖面数据。整条光缆总长2.7km，其中约2.0km用于水平地表路径的温度监测。部分光缆传感器采用1.2米高的垂直盘绕布局，以5mm的空间间隔采集从地面向上的温度剖面数据。整套监测系统于2012年10月至2014年10月的两年间持续开展观测。 该研究站点（波克弗拉特研究靶场，Poker Flat Research Range）的植被以黑云杉为主，林下发育永久冻土。研究区内的土地覆盖类型被划分为6类：残遗热融湖塘、开放苔藓群落、灌丛、落叶林、稀疏针叶林与茂密针叶林。水平温度监测数据呈现出观测到的昼夜与季节尺度上的时空变化特征，积雪演化过程与保温效应的差异与土地覆盖类型显著相关。 用于采集垂直温度剖面的监测装置，可获取空气柱、积雪覆盖层与地表的高分辨率（约5mm）观测数据。