基于地面通量观测与MODIS数据估算玉米光能利用率

Retrieval of light use efficiency of maize based on surface flux observation and MODIS data

基于地面通量数据和中分辨率成像光谱仪(Moderate-resolution Imaging Spectroradiometer, MODIS)数据,对玉米农田生态系统光能利用率(Light Use Efficiency, LUE)进行反演和分析。通过地表碳通量资料构建了玉米农田生态系统的LUE模型,分析了LUE的变化规律;通过比较不同参照波段、不同传感器角度下计算的MOIDS光化学反射植被指数(Photochemical Reflectance Index, PRI)与LUE间的关系,构建了MOIDS PRI反演玉米LUE的模型。结果表明:(1)玉米LUE呈现出明显的季节和日尺度上的变化规律,季节变化表现为单峰形,白天的LUE呈现出“U”型变化规律;(2)相比较NDVI,PRI反演植被LUE有明显优势,利用MODIS PRIS与LUE的较好相关性,建立了PRI488、PRI551和PRI667模型进行LUE反演;(3)经比较,MODIS PRIS反演LUE时最适合的为PRI551模型,其全向散射的模型具有通用性,而如果区分出后向散射数据则采用相应的PRI551后向散射模型更好;(4)利用LUEa与全天平均LUEd拟合模型与MODIS PRI551瞬时模型联合,可实现对日尺度的光能利用率的反演,其推广应用前景值得期待。

In order to investigate the latent capacity of remote sensing vegetation index in retrieving the photosynthesis of maize agro-ecosystem,eddy covariance flux data and MODIS(Moderate-resolution Imaging Spectroradiometer)data were used to retrieve and analyze the Light Use Efficiency(LUE)of maize.The results showed that:(1)The maize LUE showed obvious temporal variation on the seasonal and daily scales.The seasonal variation showed a single-peak shape,and the diurnal LUE showed a‘U-shaped’variation;(2)Compared with NDVI,the PRI(Photochemical Reflectance Index)had obvious advantages in vegetation LUE retrieval,and PRI 488,PRI 551 and PRI 667 models were established for LUE retrieval by using the good correlation between MODIS PRIS and LUE;(3)In comparison,PRI 551 was the most suitable model for retrieval of LUE from MODIS PRIS,and its omni-directional scattering model was universal.If the back scattering data were distinguished,the corresponding back scattering PRI 551 model can be better;(4)Combination of fitting model of LUE a and diurnal average LUE d with MODIS PRI 551 model can realize the retrieval of LUE on a daily scale,and its application prospect was worthy to expect.