Evidence of a topographic signal in surface soil moisture derived from ENVISAT ASAR wide swath data
Evidence of a topographic signal in surface soil moisture derived from ENVISAT ASAR wide swath data
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DOI：
10.1016/j.jag.2015.02.004
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发表时间：
2016-03
期刊：
影响因子：
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通讯作者：
D. Mason;J. García-Pintado;H. Cloke;S. Dance
中科院分区：
文献类型：
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作者：
D. Mason;J. García-Pintado;H. Cloke;S. Dance
一个集水区对洪水的敏感性受极端降雨事件前土壤湿度的影响。虽然土壤湿度是通过卫星仪器进行例行观测的，但以往关于将遥感土壤湿度同化到水文模型中的工作的结果好坏参半。这可能部分是由于所用观测的空间分辨率低。在这项研究中，遥感方面的一个项目，试图改善流量预测的分布式水文模型同化土壤水分测量。高级合成孔径雷达宽测绘带数据被用来测量土壤湿度，因为与低分辨率微波数据不同，这些数据具有足够的分辨率，可以探测到由于当地地形而引起的土壤湿度变化，这可能有助于考虑到水文过程的空间异质性。表层土壤水分含量（SSMC）的测量超过了集水区的塞文和埃文河在英国西南部。为了减少植被的影响，测量只在均匀的像素，从土地覆盖图确定的改善草地。对雷达后向散射进行了地形变化校正，并将其归一化为一个共同的入射角。SSMC的计算使用变化检测。为了寻找证据的地形信号，平均SSMC从改善草地像元在低坡度附近的河流进行比较，在较高的坡度。当低坡的平均SSMC为30 - 90%时，高坡比低坡稍干燥。较低的SSMC值的效果是相反的。在干燥事件期间也更明显。这些研究结果有助于在文献中使用高分辨率合成孔径雷达土壤水分测量，以改善水文模型的信息很少。
The susceptibility of a catchment to flooding is affected by its soil moisture prior to an extreme rainfall event. While soil moisture is routinely observed by satellite instruments, results from previous work on the assimilation of remotely sensed soil moisture into hydrologic models have been mixed. This may have been due in part to the low spatial resolution of the observations used. In this study, the remote sensing aspects of a project attempting to improve flow predictions from a distributed hydrologic model by assimilating soil moisture measurements are described. Advanced Synthetic Aperture Radar (ASAR) Wide Swath data were used to measure soil moisture as, unlike low resolution microwave data, they have sufficient resolution to allow soil moisture variations due to local topography to be detected, which may help to take into account the spatial heterogeneity of hydrological processes. Surface soil moisture content (SSMC) was measured over the catchments of the Severn and Avon rivers in the South West UK. To reduce the influence of vegetation, measurements were made only over homogeneous pixels of improved grassland determined from a land cover map. Radar backscatter was corrected for terrain variations and normalized to a common incidence angle. SSMC was calculated using change detection.To search for evidence of a topographic signal, the mean SSMC from improved grassland pixels on low slopes near rivers was compared to that on higher slopes. When the mean SSMC on low slopes was 30–90%, the higher slopes were slightly drier than the low slopes. The effect was reversed for lower SSMC values. It was also more pronounced during a drying event. These findings contribute to the scant information in the literature on the use of high resolution SAR soil moisture measurement to improve hydrologic models.