Penetration Analysis of SAR Signals in the C and L Bands for Wheat, Maize, and Grasslands
Penetration Analysis of SAR Signals in the C and L Bands for Wheat, Maize, and Grasslands
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DOI：
10.3390/rs11010031
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发表时间：
2019-01-01
期刊：
影响因子：
5
通讯作者：
Zribi, Mehrez
中科院分区：
文献类型：
--
作者：
El Hajj, Mohammad;Baghdadi, Nicolas;Zribi, Mehrez
本文评估了C和L波段合成孔径雷达（SAR）穿透小麦、玉米和草地冠层的潜力。对于小麦和草地，首先根据归一化植被指数的三个水平（NDVI < 0.4，0.4 < NDVI < 0.7，和NDVI > 0.7）研究了C和L波段对原位表层土壤水分（SSM）的敏感性。其次，根据SSM和NDVI分析了C波段和L波段SAR信号的时间演化。对于小麦和草地，结果表明，HH偏振中的L-波段穿透冠层，即使当冠层发育良好（NDVI > 0.7），而C-波段穿透冠层是有限的，当NDVI < 0.7。对于小于0.7的NDVI，雷达信号对SSM的灵敏度约为0.27 dB/vol. %对于HH极化中的L波段和大约0.12 dB/vol. %对于C波段（VV和VH偏振）。对于高度发达的小麦和草地覆盖（NDVI > 0.7），HH极化中的L波段对SSM的灵敏度约为0.19 dB/vol. %，而C波段对SSM不敏感。对于玉米，由于L波段的SAR图像条带没有覆盖玉米地块，因此仅研究了根据SSM和NDVI的C波段的时间演变。结果表明，VV极化中的C波段即使在玉米冠层发育良好（NDVI > 0. 7）的情况下也能穿透玉米冠层，这是由于在土壤-植被路径上的高阶散射沿着传播，其中包含土壤的贡献。根据本文的结果，L-波段将穿透一个发达的玉米覆盖，因为L-波段的穿透深度大于C-波段。
This paper assesses the potential of Synthetic Aperture Radar (SAR) in the C and L bands to penetrate into the canopy cover of wheat, maize and grasslands. For wheat and grasslands, the sensitivity of the C and L bands to in situ surface soil moisture (SSM) was first studied according to three levels of the Normalized Difference Vegetation Index (NDVI < 0.4, 0.4 < NDVI < 0.7, and NDVI > 0.7). Next, the temporal evolution of the SAR signal in the C and L bands was analyzed according to SSM and the NDVI. For wheat and grasslands, the results showed that the L-band in HH polarization penetrates the canopy even when the canopy is well-developed (NDVI > 0.7), whereas the penetration of the C-band into the canopy is limited for an NDVI < 0.7. For an NDVI less than 0.7, the sensitivity of the radar signal to SSM is approximately 0.27 dB/vol.% for the L-band in HH polarization and approximately 0.12 dB/vol.% for the C-band (in both VV and VH polarizations). For highly developed wheat and grassland cover (NDVI > 0.7), the sensitivity of the L-band in HH polarization to SSM is approximately 0.19 dB/vol.%, whereas as the C-band is insensitive to SSM. For maize, only the temporal evolution of the C-band according to SSM and the NDVI was studied because the swath of SAR images in the L-band did not cover the maize plots. The results showed that the C-band in VV polarization is able to penetrate the maize canopy even when the canopy is well developed (NDVI > 0.7) due to high-order scattering along the soil-vegetation pathway that contains a soil contribution. According to results obtained in this paper, the L-band would penetrate a well-developed maize cover since the penetration depth of the L-band is greater than that of the C-band.