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淮河流域GLEAM卫星土壤湿度数据评估及其时空变化规律

GLEAM Soil Moisture Data Evaluation and Its Spatiotemporal Characteristics in the Huaihe River Basin

  • 摘要: 土壤湿度是气候、水文、生态和农业等领域的重要研究对象,然而仅依赖站点土壤湿度监测无法满足大尺度区域的需要。选择淮河流域30个农气站实测土壤湿度数据评估了GLEAM卫星土壤湿度的精度。结果表明,GLEAM土壤湿度数据序列在不同站点的精度差异较明显,而在流域尺度上具有较高精度,表层和根系层土壤湿度相关系数均大于0.7;在空间分布上,卫星数据与站点实测数据均能反映流域土壤湿度分布规律,淮河南部和沂沭河沿海地区土壤湿度较大;进而采用卫星土壤湿度评估了流域1980年以来的土壤湿度变化,发现近40年来流域土壤湿度呈下降趋势的变化规律,其中春季尤为明显;由于流域旱涝年际变化影响,夏季和秋季土壤湿度的年际变率较大。

     

    Abstract: Soil moisture has been a critical research object in climate,hydrology,ecology and agriculture. However,soil moisture monitoring can not meet the needs of large-scale area applications if only relying on site data. Recent studies have shown that high-quality satellite soil moisture data is a good substitute for site data. This paper selects the observed soil moisture data of 30 agrometeorological stations to evaluate accuracy of the GLEAM satellite soil moisture in the Huaihe River Basin. Results show that:(1) Compared with the measured results of agrometeorological stations,on a single-point scale,the accuracy of the satellite soil moisture data in different stations is significantly different.In terms of watershed scale assessment,the GLEAM data has a relatively high accuracy. The correlation coefficient of soil moisture in both surface and root zone layer is more than 0.7,among which the surface layer is close to the mean value of the measured data and the soil moisture in root zone layer is somewhat underestimated.(2) In terms of spatial distribution,both GLEAM and agrometeorological stations data show that the soil moisture in the Huaihe River Basin is high in the south and low in the north,high in the east and low in the west,while soil moisture in the southern Huaihe River and the coastal areas of Yi and Shu River is relatively large. Based on the advantages of wide range and continuous space of satellite soil moisture monitoring,it is suggested that it should be used in large-scale regional soil moisture research.(3)The average soil moisture in the Huaihe River Basin has a significant inter-annual change. Since 1980,soil surface layer and root zone layer have shown a downward trend,especially in spring. The inter-annual variation of soil moisture in summer and autumn is large due to the influence of inter-annual variation of drought and flood in the basin. Overall,the GLEAM satellite data has relatively high precision and good stability in the basin scale assessment,which can make up for the lack of site monitoring data,and has an important application prospect in the basin agricultural production,flood forecasting,drought assessment and water resources assessment.

     

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