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首页> 外文会议>Remote sensing for agriculture, ecosystems, and hydrology XIII >Improvement of the Triangle method for soil moisture evaluation by adding a third index: albedo or Cellulose Absorption Index
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Improvement of the Triangle method for soil moisture evaluation by adding a third index: albedo or Cellulose Absorption Index

机译：通过增加第三个指标：反照率或纤维素吸收指数，改进了三角法在土壤水分评估中的应用

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摘要

Vegetation and soil temperatures have long been recognized as an indicator of water availability. When plotting the two-dimensional distribution of temperature and vegetation index (T-VI) corresponding to an area with well distributed vegetation cover and moisture content, one gets a triangular or trapezoidal shape. Iso-moisture lines range between two edges of the distribution: the dry edge and the wet edge. This description is based on a simplified representation of the thermal and radiative properties of the soil/vegetation structure and of the heat and mass transfer. A large number of parameters, in addition to soil moisture, are actually influencing the apparent soil/canopy temperature. Stretching the temperature distribution along only one dimension like the VI is indeed not enough for allowing an unambiguous determination of soil moisture. We propose to improve the identifiability of soil moisture by introducing an additional observable parameter: albedo or CAI (Cellulose Absorption Index). Albedo was chosen to separate areas according to the absorbed solar radiation whereas CAI was chosen to separate areas according to the fraction of senescent vegetation. The aim of this study is to analyze the benefit of adding a third index to the classical T-VI empirical method for soil moisture mapping. The proposed procedures were applied on remote sensing data obtained during two airborne campaigns: HyEurope 2007 and AgriSAR 2006. In the first case, when applying the 2D trapezoid method, the coefficient of determination between the inferred moisture index and the gravimetric moisture content reaches 0.61. It slightly diminishes to 0.59 when adding albedo whereas it increases to 0.69 when adding CAI instead. Therefore adding albedo doesn't seem to provide an improvement, at least for the considered cropland. The introduction of the Cellulose Absorption Index seems to be more promising. The crops during AgriSAR 2006 campaign presented in July a too high LAI whereas the soil surface was generally very dry. These conditions prevented to draw any significant conclusion. Better results are expected to be met for areas presenting lower vegetation cover as for example semi-arid regions.
机译：长期以来，植被和土壤温度一直被认为是水供应的指标。当绘制与植被覆盖和水分含量分布良好的区域相对应的温度和植被指数（T-VI）的二维分布时，将呈现三角形或梯形形状。等水分线分布在分布的两个边缘之间：干边缘和湿边缘。该描述基于土壤/植被结构的热和辐射特性以及热和质量传递的简化表示。除了土壤湿度外，大量参数实际上还会影响表观土壤/冠层温度。像VI一样仅沿一个维度拉伸温度分布确实不足以明确确定土壤湿度。我们建议通过引入一个附加的可观察参数：反照率或CAI（纤维素吸收指数）来提高土壤水分的可识别性。根据吸收的太阳辐射选择反照率来分隔区域，而根据衰老植被的比例选择CAI来分隔区域。这项研究的目的是分析在传统的T-VI经验方法中为土壤水分测绘添加第三个指标的好处。拟议的程序适用于两次空中战役中获得的遥感数据：HyEurope 2007和AgriSAR2006。在第一种情况下，当使用2D梯形法时，推断的水分指数和重量水分含量之间的确定系数达到0.61。添加反照率时略微降低至0.59，而添加CAI时则增加至0.69。因此，至少对于所考虑的耕地，添加反照率似乎并没有改善。引入纤维素吸收指数似乎更有希望。 7月的AgriSAR 2006运动期间，农作物的LAI值过高，而土壤表面通常非常干燥。这些条件无法得出任何重大结论。对于植被覆盖率较低的地区（例如半干旱地区），有望获得更好的结果。

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