植被结构特征对MODIS光谱干旱指数的影响

基于MODIS光谱反射信息的干旱指数在农业生产实践中有广泛的应用。利用PROSAIL模型和山东2010年的观测数据，研究了植被叶面积指数和生理生长周期等结构特征对MODIS光谱干旱指数的影响。结果表明，MODIS近红外与短波红外三个波段的反射率随植被叶片含水量变化明显，由他们构建的五种MODIS光谱干旱指数能够监测植被叶片水分含量。然而，各干旱指数均受叶面积指数(LAI)的影响，在LAI较低时影响较为严重，随着LAI的增大，这一影响逐渐减弱;植被生理生长周期也会影响干旱指数的大小。因此，在使用MODIS光谱干旱指数进行区域干旱监测时，必须考虑植被结构特征，谨慎分析监测结果。研究结论将为干旱遥感监测提供理论基础。

Impact of Vegetation Structure on Drought Indices Based on MODIS Spectrum

The drought indices based on MODIS spectral reflectance data are widely used for drought characterization and monitoring in agricultural context. Based on the PROSAIL model and MODIS observational data in Shandong in 2010, the present paper studied the impact of vegetation structure of leaf area index and physiological growth cycle on MODIS spectral drought index. The results showed that the reflectance of three MODIS bands in spectrum of near-infrared and shortwave infrared changes significantly with leaf water content of vegetation. Therefore, the five kinds of MODIS spectral drought index constructed by those MODIS bands can be used to monitor the leaf water content of vegetation. However, all drought indices are affected by leaf area index. In general, the impact is serious in the case of low LAI values and is weakened with the increase in LAI value. The study found that physiological vegetation growth cycle also affects the magnitude of MODIS spectral drought indices. In conclusion, the impact of vegetation structure must be carefully considered when using MODIS spectral drought indices to monitor drought. The conclusion of this study provides a theoretical basis for remote sensing of drought monitoring.