融合多源数据的高分辨率土壤水分模拟模型构建及应用

    Construction and application of a high-resolution soil moisture simulation model integrating multi-source data

    • 摘要: 实时动态高分辨率土壤水分产品可为区域农业生产安全保障提供重要支撑,目前常用的土壤水分遥感产品存在空间分辨率较低及时间序列不连续等问题。为了生成时空连续的高分辨率土壤水分结果,该研究引入集成学习中的随机森林(random forest, RF)和梯度提升机(grandient boosting machine, GBM)算法,构建了融合多源数据的高分辨率土壤水分模拟(high-resolution soil moisture simulation, HRSMS)模型。2017—2022年SMAP微波土壤水分、植被指数、地表温度等遥感数据和墒情站点实测数据为模型输入和输出,利用Savitzky-Golay滤波方法和多元回归方法填补缺失的植被指数和地表温度数据,基于RF和GBM算法实现SMAP表层(0~5 cm)土壤水分数据分辨率提升(从9 km提高至1 km)。以吉林省为例验证模型可行性,结果表明:1)HRSMS模型相较于常用的多项式回归拟合法精度显著提升。均方根误差(root mean square error, RMSE)、平均绝对误差(mean absolute error, MAE)较多项式回归拟合法精度降低了22.2%、44.0%,决定系数(R2)提高了0.27,西北部粮食主产区的误差减少了33.2%;2)HRSMS模型中,RF与GBM算法计算效能相近,RF算法R2、RMSE、MAE分别高于GBM算法4.9%、0.7%、2.3%,在吉林省开展相关研究时可结合数据条件任选其一进行模型构建。HRSMS模型有效提升了土壤水分遥感数据产品的分辨率和精度,对进一步提升土壤水分精准监测能力具有重要意义。

       

      Abstract: Real-time dynamic high-resolution soil moisture products can provide important support for regional agricultural production safety and security, and the current commonly used soil moisture remote sensing products have problems of spatial resolution and time series continuity. In order to generate spatio-temporally continuous high-resolution soil moisture results, we introduced the random forest (RF) and gradient boosting machine (GBM) algorithms in ensemble learning, and innovatively constructed a high-resolution soil moisture simulation (HRSMS) model integrating multi-source data. Input data comprised microwave soil moisture observations from the soil moisture active passive (SMAP) mission (2017–2022), vegetation indices, land surface temperature, and in-situ soil moisture measurements. Missing values in vegetation indices and temperature datasets were reconstructed using Savitzky-Golay filtering and multivariate regression. The model downscaled SMAP-derived surface soil moisture (0~5 cm depth) from 9 km to 1 km resolution. Validation was conducted in Jilin Province, a major agricultural region in northeastern China, and the results of the study indicated that: 1) The accuracy of HRSMS model was significantly improved compared to the commonly used polynomial regression fitting method. The root mean square error (RMSE), mean absolute error (MAE), and r square (R2) improved by 22.2%, 44.0%, and 0.27 compared to the polynomial regression fitting method, and the error was reduced by 33.2% in the main grain producing areas of northwestern Jilin Province; 2) In the HRSMS model, RF and GBM algorithms have similar computational efficiency, and RF algorithm R2, RMSE, and MAE are higher than GBM algorithm by 4.9%, 0.7%, and 2.3%, respectively, and therefore either algorithm can be selected for model construction when carrying out related research in Jilin Province. The HRSMS framework effectively improved both spatial resolution and accuracy of soil moisture products while maintaining temporal consistency. This advancement supports precision agriculture through enhanced soil moisture monitoring capabilities. The operational flexibility between RF and GBM algorithms provides adaptability for diverse regional data conditions. The methodology holds significant potential for scaling to other agricultural regions requiring high-resolution soil moisture assessments.

       

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