In‐situ probe spacing calibration improves the heat pulse method for measuring soil heat capacity and water content
In‐situ probe spacing calibration improves the heat pulse method for measuring soil heat capacity and water content
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DOI：
10.1002/saj2.20124
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发表时间：
2020-09
影响因子：
2.9
通讯作者：
Meng Zhang;Yili Lu;T. Ren;R. Horton
中科院分区：
文献类型：
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作者：
Meng Zhang;Yili Lu;T. Ren;R. Horton
热脉冲（HP）传感器已广泛用于同时测量土壤热性质和体积含水量（θ）。探头间距（R），即加热器探头和温度探头之间的距离，在进行HP测量之前在琼脂溶液中进行常规校准。实际上，R可能会因探头插入土壤时的偏转而发生变化，从而导致HP测得的体积热容（C）和θ的不确定性。在本文中，我们提出了一种简单的现场校准方法，通过使用从土壤容重估计的理论C值和在实验结束时在传感器位置附近收集的完整土芯的θ值来确定in-situ R。在两个连续监测C和θ的田间土壤上对所提出的方法进行了测试。琼脂校准R值（Ragar）和原位校准R值（Rin situ）之间观察到不一致的结果。Ragar和Rin-situ之间的最大差异达到Ragar的20%。与TDR测量的θ相比，使用Ragarled的均方根误差（RMSE）平均为0.26 MJ m− 3 K − 1 in C和0.06 m3 m − 3 in θ。对于R原位，C的RMSE小于0.16 MJ m− 3 K − 1，θ的RMSE在0.04 m3 m −3以内。因此，使用现场探头间距校准提高了HP测量C和θ的准确性。
Heat pulse (HP) sensors have been used extensively to measure soil thermal properties and volumetric water content (θ) simultaneously. Probe spacing (R), the distance between heater probe and temperature probe, is routinely calibrated in agar solution before making HP measurements. In reality,Rmay change due to probe deflection at insertion into soil, causing uncertainties in HP measured volumetric heat capacity (C) and θ. In this paper, we present a simple on‐site calibration method for determining in‐situRby using theoreticalCvalues estimated from soil bulk density and θ values of intact soil cores collected near the sensor locations at the end of experiment. The proposed approach was tested on two field soils whereCand θ were monitored continuously. Inconsistent results were observed between agar‐calibratedRvalues (Ragar) andRvalues obtained from in‐situ calibration (Rin‐situ). Maximum difference betweenRagarandRin‐situreached 20% ofRagar. Compared to TDR measured θ, usingRagarled to root mean square errors (RMSEs) of 0.26 MJ m−3K−1inCand 0.06 m3m−3in θ on average. ForRin‐situ, the RMSE ofCwas less than 0.16 MJ m−3K−1and RMSE of θ was within 0.04 m3m−3. Thus, the use of in‐situ probe spacing calibration improved the accuracies of HP measuredCand θ.