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首页> 外文期刊>Water resources research >Field testing of the universal calibration function for determination of soil moisture with cosmic-ray neutrons
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Field testing of the universal calibration function for determination of soil moisture with cosmic-ray neutrons

机译：使用宇宙射线中子测定土壤水分的通用校准功能的现场测试

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The semitheoretical universal calibration function (UCF) for estimating soil moisture using cosmic-ray neutron sensors was tested by comparing to field measurements made with the same neutron detector across a range of climates, soil, latitude, altitude, and biomass. There was a strong correlation between neutron intensity and the total amount of hydrogen at each site; however, the relationship differed from that predicted by the UCF. A linear fit to field measurements explained 99% of the observed variation and provides a robust empirical means to estimate soil moisture at other sites. It was concluded that measurement errors, neutron count corrections, and scaling to remove altitudinal and geomagnetic differences were unlikely to explain differences between observations and the UCF. The differences may be attributable to the representation of organic carbon, biomass or detector geometry in the neutron particle code, or to differences in the neutron energy levels being measured by the cosmic-ray sensor and modeled using the particle code. The UCF was derived using simulations of epithermal neutrons; however, lower energy thermal neutrons may also be important. Using neutron transport code, we show the differences in response of thermal and epithermal neutrons to the relative size of the hydrogen pool. Including a thermal neutron component in addition to epithermal neutrons in a modified UCF provided a better match to field measurements; however, thermal neutron measurements are needed to confirm these results. A simpler generalized relationship for estimating soil moisture from neutron counts was also tested with encouraging results for low biomass sites.
机译：通过与使用同一中子探测器在各种气候，土壤，纬度，高度和生物量范围内进行的现场测量结果进行比较，测试了使用宇宙射线中子传感器估算土壤湿度的半理论通用校准函数（UCF）。每个位置的中子强度与氢总量之间存在很强的相关性。但是，这种关系不同于UCF预测的关系。对田间测量的线性拟合解释了观测到的变化的99％，并提供了可靠的经验手段来估算其他地点的土壤湿度。得出的结论是，测量误差，中子计数校正和去除垂直和地磁差异的缩放不可能解释观测值与UCF之间的差异。差异可归因于中子粒子代码中有机碳，生物量或检测器几何形状的表示，或者归因于由宇宙射线传感器测量并使用粒子代码建模的中子能级的差异。 UCF是使用超热中子的模拟得出的。但是，低能热中子也可能很重要。使用中子传输代码，我们显示了热中子和超热中子对氢池相对大小的响应差异。在改进的UCF中，除了超热中子外还包括热中子成分，可以更好地匹配现场测量；但是，需要进行热中子测量以确认这些结果。还测试了一种用于根据中子计数估算土壤湿度的更简单的广义关系，对于低生物量场所，结果令人鼓舞。

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