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基于多源遥感数据的夏玉米覆盖地表土壤水分协同反演研究

Collaborative Inversion of Soil Moisture over Summer Maize Covered Surfaces Based on Multi-source Remote Sensing Data

  • 摘要: 土壤水分是陆-气界面物质与能量交换的关键参数,及时、准确地获取土壤水分信息,对于旱情监测、水资源管理以及农作物估产等具有重要意义。研究基于Sentinel-1 SAR遥感数据与Sentinel-2光学遥感数据,系统分析了不同光学植被指数与实测植被含水量之间的关系,优选融合植被指数(Fusion Vegetation Index,FVI)建立植被含水量估测模型,将其与植被微波散射模型—水云模型(Water Cloud Model,WCM)相结合,校正了植被层对SAR后向散射信号的影响。在此基础上,利用地表微波散射模型—Oh模型构建后向散射系数模拟数据库,基于查找表(Look Up Table, LUT)算法实现了VV和VH两种极化方式下夏玉米覆盖地表的土壤水分反演。结果表明:对于夏玉米等浓密植被覆盖地表,FVI能够更好地反映植被含水量特征,从而准确校正植被层的后向散射贡献量,基于FVI构建的植被含水量反演模型R2为0.693,RMSE为0.303 kg/m2;植被校正后,VV和VH极化方式下土壤水分与SAR总后向散射系数之间的相关性分别提高了21.6%和27.9%;相比于VH极化方式,VV极化方式更适用于土壤水分的反演,夏玉米覆盖地表土壤水分反演结果与实测值之间的R2为0.672,RMSE为0.048 m3/m3。研究成果可为浓密植被覆盖下土壤水分的遥感观测提供有力支撑。

     

    Abstract: Soil moisture is a crucial parameter for the exchange of matter and energy at the land-atmosphere interface. Timely and accurate acquisition of soil moisture information is of paramount importance for drought monitoring, water resource management, and crop yield estimation. In this study, utilizing Sentinel-1 SAR remote sensing data and Sentinel-2 optical remote sensing data, the relationship between various optical vegetation indices and measured vegetation water content was systematically analyzed. The Fusion Vegetation Index(FVI) was preferentially selected to establish vegetation water content estimation model,which was combined with the vegetation microwave scattering model—Water Cloud Model(WCM) to correct the impact of vegetation layer on SAR backscattering signals. On this basis, a surface microwave scattering model—Oh model was used to construct the backscattering coefficient simulation database, and soil moisture retrieval for the summer maize-covered surface under both VV and VH polarizations was achieved through the application of the Look-Up Table(LUT) algorithm. The results indicate that, for surfaces covered by dense vegetation like summer maize, vegetation water content characteristics can be better reflected by FVI, enabling the accurate correction of the impact of vegetation layers on SAR backscattering coefficients. The vegetation water content inversion model based on FVI achieved an R2 of 0.693 and an RMSE of 0.303 kg/m2. After vegetation correction, the correlation between soil moisture and SAR backscattering coefficients increased by 21.6% and 27.9% for VV and VH polarizations, respectively. Compared to VH polarization, VV polarization is found to be more suitable for soil moisture retrieval, with an R2 of 0.672 and an RMSE of 0.048m3/m3 between retrieved and measured soil moisture values. The findings of this study provide robust support for the remote sensing observation of soil moisture information in densely vegetated surfaces.

     

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