Soil Temperature Variability in Complex Terrain Measured Using Fiber-Optic Distributed Temperature Sensing

Soil temperature (Ts) exerts critical controls on hydrologic and biogeochemical processes, but the magnitude and nature of Ts variability in a landscape setting are rarely documented. Fiber-optic distributed temperature sensing (DTS) systems potentially measure Ts at high density across a large extent. A fiber-optic cable 771 m long was installed at a depth of 10 cm in contrasting landscape units (LUs) defined by vegetative cover at Upper Sheep Creek in the Reynolds Creek Experimental Watershed (RCEW) and Critical Zone Observatory in Idaho. The purpose was to evaluate the applicability of DTS in remote settings and to characterize Ts variability in complex terrain. Measurement accuracy was similar to other field instruments (±0.4°C), and Ts changes of approximately 0.05°C at a monitoring spatial scale of 1 m were resolved with occasional calibration and an ambient temperature range of 50°C. Differences in solar inputs among LUs were strongly modified by surface conditions. During spatially continuous snow cover, Ts was practically homogeneous across LUs. In the absence of snow cover, daily average Ts was highly variable among LUs due to variations in vegetative cover, with a standard deviation (SD) greater than 5°C, and relatively uniform (SD < 1.5°C) within LUs. Mean annual soil temperature differences among LUs of 5.2°C was greater than those of 4.4°C associated with a 910-m elevation difference within the RCEW. In this environment, effective Ts simulation requires representation of relatively small-scale (<20 m) LUs due to the deterministic spatial variability of Ts.

Raw project data is available by contacting [e-mail]

土壤温度（Ts）对水文和生物地球化学过程具有至关重要的调控作用，然而，在景观环境中，Ts的变幅及其性质却鲜有详尽的记录。光纤分布式温度传感（DTS）系统有望在大范围内以高密度测量Ts。在爱达荷州雷诺斯溪实验流域（RCEW）和临界带观测站的上羊溪，于植被覆盖差异明显的景观单元（LU）中，安装了一条长度为771米的光纤电缆，深度为10厘米。其目的是评估DTS在偏远环境中的应用可行性，并描绘复杂地形中Ts的变异性。测量精度与其他野外仪器相似（±0.4°C），在1米的监测空间尺度上，偶尔校准并在环境温度范围为50°C的情况下，可分辨出约0.05°C的Ts变化。LU之间的太阳辐射输入差异受到地表条件的强烈调节。在连续的积雪覆盖期间，LU内的Ts几乎均匀一致。在无积雪覆盖的情况下，由于植被覆盖的变化，LU间的日平均Ts存在高度可变性，标准差（SD）超过5°C，而LU内的变异性相对均匀（SD < 1.5°C）。LU间的年均土壤温度差异为5.2°C，大于RCEW内910米海拔差异所对应的4.4°C。在此环境中，有效的Ts模拟需要表征相对较小的尺度（<20米）的LU，因为Ts的确定性空间变异性较大。

原始项目数据可通过联系 [e-mail] 获取。