Abstract

Soil moisture is an important variable in the agriculture system. Likewise, accurate information on soil moisture is needed for the effective modeling of many hydrological and climatological processes. Synthetic Aperture Radar (SAR) operates with the competence to acquire data in any weather condition, has been proved to be sensitive to surface soil moisture. This study has attempted to establish simple experimental relationships to estimate volumetric bare surface soil moisture (sm_v) using the SAR satellite-based radar backscatter values (σ°). In this study, the in-situ sm_v measurements of two study sites in the United States were obtained from the SoilSCAPE project whereas σ° data for the same study sites were obtained from the C-band Sentinel-1 satellite. Initially, four experiments were designed based on various radar configurations i.e., combination of polarization and incidence angle(s) at an individual or combined node(s) of each study site. Following this, the statistical analysis in each experiment was carried out using the high volume data i.e., the long-term time-series σ° and in-situ sm_v that were clustered in these radar configurations. Subsequently, the relationships were established on the basis of outcome of each experiment. Based on the detailed analysis, it was found that out of four experiments, only one experiment outcome in terms of correlations statistics, for a particular radar configuration and study site, was found to be significant and accepted for model development. The derived model was applied and validated over the demo farm located in Pune, India. The comparison between the estimated and in-situ sm_v measurements shows good agreement, with a mapping accuracy of about 8% observed with the radar configuration- vertical-vertical (VV) polarization with a 43° incidence angle.

摘要

土壤水分是农业系统中的一个重要变量。同样，对于许多水文和气候过程的有效建模也需要准确的土壤水分信息。合成孔径雷达 (SAR) 具有在任何天气条件下获取数据的能力，已被证明对地表土壤水分敏感。本研究试图建立简单的实验关系，使用基于 SAR 卫星的雷达后向散射值 ( σ °)来估计体积裸露地表土壤水分 ( sm _{v )。}在这项研究中，美国两个研究地点的原位sm _v测量值来自 SoilSCAPE 项目，而σ°相同研究地点的数据来自 C 波段 Sentinel-1 卫星。最初，基于各种雷达配置设计了四个实验，即在每个研究站点的单个或组合节点处的偏振和入射角的组合。在此之后，每个实验中的统计分析都是使用大量数据进行的，即长期时间序列σ ° 和原位sm _v聚集在这些雷达配置中。随后，根据每个实验的结果建立关系。根据详细分析，发现在四个实验中，只有一个在相关统计方面的实验结果，对于特定的雷达配置和研究地点，被发现具有重要意义并被模型开发接受。派生模型在位于印度浦那的演示农场应用和验证。估计和原位sm _v测量值之间的比较显示出良好的一致性，在 43° 入射角的雷达配置 - 垂直 - 垂直 (VV) 极化下观察到的映射精度约为 8%。