不同质量含水量的土壤反射率光谱模拟模型

Modeling Soil Spectral Reflectance with Different Mass Moisture Content

土壤含水量的时空分布与变化情况对土壤温度变化、陆地—大气间热量平衡以及陆面大气环流产生显著的影响,因此,对大范围内土壤含水量进行实时动态监测,获得某段时间内土壤含水量的连续变化情况具有重要的意义。研究目的是借助高光谱遥感手段,通过构建不同质量含水量的土壤反射率光谱模拟模型,深入了解土壤质量含水量与土壤反射率光谱之间的关系,为监测土壤含水量提供有效手段。利用ASD Field Spectral FR野外光谱仪和加水称重法获得北京市8个采样点的土壤样品不同质量含水量下的土壤反射率光谱实测数据,利用其中2个土壤样品不同质量含水量下的光谱数据构建含水土壤反射率光谱模拟模型,并利用未参与建模的另外6个土壤样品数据对该模型的模拟效果进行了检验。通过数据验证发现,当土壤质量含水量小于田间持水量时,该模型的模拟精度较高;而且对于不同的土壤样品,模型的模拟效果都比较好。最后又利用北京大学校园内三个采样点的实地测量光谱数据对模型进行了验证,光谱的模拟值与实测值之间的均方根误差最小可达0.005 8。因此该模型可实现对质量含水量小于田间持水量的不同类型土壤的反射率光谱进行较高精度的模拟。

The spatio-temporal distribution and variation of soil moisture content have a significant impact on soil temperature,heat balance between land and atmosphere and atmospheric circulation.Hence,it is of great significance to monitor the soil moisture content dynamically at a large scale and to acquire its continuous change during a certain period of time.The object of this paper is to explore the relationship between the mass moisture content of soil and soil spectrum.This was accomplished by building a spectral simulation model of soil with different mass moisture content using hyperspectral remote sensing data.The spectra of soil samples of 8sampling sites in Beijing were obtained using ASD Field Spectrometer.Their mass moisture contents were measured using oven drying method.Spectra of two soil samples under different mass moisture content were used to construct soil spectral simulation model,and the model was validated using spectra of the other six soil samples.The results show that the accuracy of the model is higher when the mass water content of soil is below field capacity.At last,we used the spectra of three sampling points on campus of Peking University to test the model,and the minimum value of root mean square error between simulated and measured spectral reflectance was 0.005 8.Therefore the model is expected to perform well in simulating the spectrum reflectance of different types of soil when mass water content below field capacity.