Abstract
Abstract. A modified two-scale microwave scattering model (MTSM) was presented to describe the scattering coefficient of natural rough surface in this paper. In the model, the surface roughness was assumed to be Gaussian so that the surface height z(x, y) can be split into large-scale and small-scale components relative to the electromagnetic wavelength by the wavelet packet transform. Then, the Kirchhoff Model (KM) and Small Perturbation Method (SPM) were used to estimate the backscattering coefficient of the large-scale and small-scale roughness respectively. Moreover, the ‘tilting effect’ caused by the slope of large-scale roughness should be corrected when we calculated the backscattering contribution of the small-scale roughness. Backscattering coefficient of the MTSM was the sum of backscattering contribution of both scale roughness surface. The MTSM was tested and validated by the advanced integral equation model (AIEM) for dielectric randomly rough surface, the results indicated that, the MTSM accuracy were in good agreement with AIEM when incident angle was less than 30° (θi <30°) and the surface roughness was small (ks = 0.354).
Highlights
The research on the scattering model for the randomly rough surface is an important part of microwave remote sensing theory
While at large incident angles, the scattering is dominated by small-scale surface roughness which is tilted by the slope of the large-scale surface roughness; So Small Perturbation Model (SPM) is used to account for the tilting effect by introducing a local coordinate system and the scattering coefficient is calculated by considering both the large-scale and small-scale roughness
The advanced integral equation model (AIEM), which is the improvement of Integral Equations Model (IEM), was adopted to verify the MTSM in this paper
Summary
The research on the scattering model for the randomly rough surface is an important part of microwave remote sensing theory. IEM extends the valid rang of the theoretical scattering model and fills up parts of the gap between KM and SPM, it is the most popular method used in calculation of electromagnetic scattering of natural surface. While at large incident angles (θi>25°), the scattering is dominated by small-scale surface roughness which is tilted by the slope of the large-scale surface roughness; So SPM is used to account for the tilting effect by introducing a local coordinate system and the scattering coefficient is calculated by considering both the large-scale and small-scale roughness Brown proposed another two-scale model (Brown, 1978), a kind of Fourier function is used to transform the surface height to spectrum domain for a perfectly Gaussian surface, where the surface is filtered in its height spectral domain by a low pass. The final result is the sum of the contribution of both scale surface roughness
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