Calculations of the Microwave Brightness Temperature of Rough Soil Surfaces: Bare Field
Calculations of the Microwave Brightness Temperature of Rough Soil Surfaces: Bare Field
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DOI：
10.1109/tgrs.1987.289780
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发表时间：
1987
影响因子：
8.2
通讯作者：
T. Mo;T. Schmugge;James R. Wang
中科院分区：
文献类型：
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作者：
T. Mo;T. Schmugge;James R. Wang
建立了一个粗糙土壤微波亮温遥感模拟模型。土壤介质的表面发射率由1减去其反射率计算，该反射率由粗糙土壤表面的双站散射系数的积分获得。土壤亮温由地表发射率和有效土壤温度的乘积得到，有效土壤温度由不同深度的实测土壤水分剖面和土壤温度剖面计算得到。土壤表面的粗糙度由两个参数表征，表面高度标准差a及其水平相关长度l。模型计算进行了比较，在两个L波段（1.4 GHz）和C波段（5 GHz）频率的偏振亮度温度的测得的角度变化。使用非线性最小二乘拟合方法将模型计算与数据相匹配，最佳拟合结果产生最能表征表面粗糙度的参数值a和l。通过引入阴影函数S（<$），粗糙表面阴影的影响也被纳入模型中，该阴影函数表示粗糙表面上的点不被表面的其他部分阴影的概率。水平极化的模型结果与数据在定性和定量上都非常吻合。对于垂直极化，计算结果与实测数据存在一定的差异。可能的差异的原因进行了讨论。
A model for simulating the remotely sensed microwave brightness temperatures of soils with rough surfaces is developed. The surface emissivity of the soil media is calculated from one minus its reflectivity, which is obtained by the integration of the bistatic scattering coefficients for rough soil surfaces. The soil brightness temperature is obtained from the product of the surface emissivity and the effective soil temperature, which is calculated with measured soil moisture profiles and soil temperature profiles at various soil depths. The roughness of a soil surface is characterized by two parameters, the surface height standard deviation a and its horizontal correlation length l. The model calculations are compared to the measured angular variations of the polarized brightness temperatures at both L-band (1.4 GHz) and C-band (5 GHz) frequencies. A nonlinear least squares fitting method is used to match the model calculations with the data, and the best fit results produce the parameter values of a and l that best characterize the surface roughness. The effect of rough surface shadowing is also incorporated into the model by introducing a shadowing function S(¿), which represents the probability that a point on a rough surface is not shadowed by other parts of the surface. The model results for horizontal polarization are in excellent agreement with the data, both qualitatively and quantitatively. For vertical polarization, some discrepancies exist between the calculations and data. Possible causes of the discrepancy are discussed.