Spatio-temporally continuous temperature monitoring using optical fibers (Loop1) in the internal forest areas at Alaska in 2018

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.本研究采用基于拉曼散射光时域反射技术的光纤分布式温度传感（DTS, distributed temperature sensing）系统，对阿拉斯加内陆的寒温带森林研究站点开展监测。该站点地表温度冬季最低可达-40℃，夏季最高为30℃。 在平行对照实验中，一套多模渐变折射率GI50/125双芯光纤线缆传感器系统（外径3.4mm）以高分辨率模式开展监测：每30分钟采集一次数据，空间采样间隔为0.5m，用于获取区域内地表温度的空间分布。此外，研究人员在地表上方1米高度处采集了高分辨率垂直温度剖面数据。整套光纤线缆总长2.7km，其中约2.0km用于水平地表路径的温度监测。部分线缆传感器采用垂直盘管布设方式（高度1.2m），以5mm的间隔采集从地面向上的温度剖面数据。整个监测周期为2012年10月至2014年10月，共计2年连续观测。 该站点（波克尔弗莱研究靶场, Poker Flat Research Range）的植被以黑云杉为主，下伏永久冻土。研究区内的土地覆盖类型可分为六类：残余热喀斯特湖、开阔苔藓生境、灌丛、落叶林、稀疏针叶林以及茂密针叶林。水平温度数据呈现出观测范围内的昼夜与季节时空动态变化特征。积雪演化过程与保温效应的差异与土地覆盖类型协同变化。 用于监测垂直温度剖面的观测装置，可获取空气柱、积雪覆盖层及地表的高分辨率（约5mm）监测数据。