Relating soil surface moisture to reflectance
Relating soil surface moisture to reflectance
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DOI：
10.1016/s0034-4257(01)00347-9
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发表时间：
2002-08-01
影响因子：
13.5
通讯作者：
Zhang, B
中科院分区：
文献类型：
--
作者：
Liu, WD;Baret, F;Zhang, B
本研究的目的是探讨土壤反射率在太阳域（400-2500 nm）和土壤水分之间的关系。对10种土壤进行了取样，土壤成分范围很广。为了减少数据集的大维度，我们通过简单的逐步线性回归减少了研究的波段数量。七个波段被选中，这代表了整个光谱域的10种土壤和所有水分条件的均方根误差（RMSE）优于0.002，接近实验的不确定性。每一个土壤反射光谱归一化的相应的反射光谱下观察到的最干燥的条件。这样可以最大限度地减少土壤类型以及其他不良倍增因素（如粗糙度和测量配置）的影响。然后研究了归一化土壤反射率与湿度之间的关系。对于所有的波长和所有的土壤，结果表明，对于低土壤水分水平，反射率下降时，水分增加。相反，在临界点之后，土壤反射率随着土壤湿度的增加而增加。对于某些土壤，最潮湿条件下的反射率可以超过最干燥条件下的反射率。临界点的位置与土壤水动力学性质有关。对于低和高土壤水分水平，以及所选的七个波长，相对反射率与水分密切相关。调整不同土壤类型的关系，可以提供更好的土壤水分反演性能。它还表明，一般的关系是非线性的。这些结果进行了讨论，关于基本的物理过程，以及应用到土壤水分的反射率测量估计。(C)2002年爱思唯尔科技有限公司All rights reserved.
The objective of this study was to explore the relationship between soil reflectance in the solar domain (400-2500 nm) and soil moisture. Ten soils covering a large range of composition have been sampled. To decrease the large dimensionality of the data set, we reduced the number of wavebands investigated thanks to a simple stepwise linear regression. Seven wavebands were selected, which represent the whole spectral domain for the 10 soils and all moisture conditions with a root mean square error (RMSE) better than 0.002, close to the experimental uncertainties. Each soil reflectance spectrum was normalized by the corresponding reflectance spectrum observed under the driest condition. This allows to minimize effects due to soil type, as well as those of other undesirable multiplicative factors such as roughness and measurement configuration. The relationship between the normalized soil reflectance and moisture was then investigated. For all the wavelengths and all the soils, results show that for low soil moisture levels, the reflectance decreased when the moisture increased. Conversely, after a critical point, soil reflectance increased with soil moisture. For some soils, the reflectance of the wettest conditions can overpass that of the driest conditions. The position of the critical point was related to soil hydrodynamic properties. For both low and high soil moisture levels, and the seven wavelengths selected, the relative reflectance was strongly correlated with moisture. Adjustment of the relationships over individual soil types provides better soil moisture retrieval performances. It also shows that the relationships are generally nonlinear. These results are discussed with regards to the underlying physical processes, as well as for application to soil moisture estimates from reflectance measurements. (C) 2002 Elsevier Science Inc. All rights reserved.