新植被水分指数的冬小麦冠层水分遥感估算

水分含量是表征作物水分胁迫生理状况的重要指标，及时有效地监测作物水分含量对于评估作物水分盈亏平衡，指导农业生产灌溉具有重要意义。针对不同形式的归一化差值水分指数(NDWI)存在的饱和性问题，拟引入增强型植被指数EVI对其加以适当改进，通过构建新的植被水分指数NDWI#(即NDWI*EVI)来估算作物水分含量。首先，利用PROSAIL辐射传输模型分析了由不同水分敏感波段(1 240，1 450，1 950和2 500 nm)构建的各种典型NDWIs与相应新植被水分指数NDWI#对植被冠层水分及LAI的饱和响应特征;然后，利用田间实验光谱和水分数据，开展作物水分含量的建模和验证分析。结果表明：将EVI引入后，形成的新水分指数NDWI#能够有效提高冬小麦水分含量估算精度，特别是针对NDWI₁₄₅₀，NDWI₁₉₄₀，NDWI₂₅₀₀这三个指数，改进后的新指数显著提高了对LAI响应的饱和点，冬小麦作物水分估算精度也得到较为的明显改善。研究表明，将含有可见光波段信息的EVI引入到NDWI中，构建的新指数NDWI#因融合可见光、近红外和短波红外更多波段的光谱信息，对估算冬小麦冠层含水量可能具有更好的优势。

Estimating Canopy Water Content in Wheat Based on New Vegetation Water Index

Moisture content is an important indicator for crop water stress condition, timely and effective monitoring crop water content is of great significance for evaluate crop water deficit balance and guide agriculture irrigation. In order to improve the saturated problems of different forms of typical NDWI (Normalized Different Water Index), we tried to introduce EVI(Enhanced Vegetation Index) to build new vegetation water indices(NDWI#) to estimate crop water content. Firstly, PROSAIL model was used to study the saturation sensitivity of NDWI_s and NDWI# to canopy water content and LAI(Leaf Area Index). Then, the estimated model and verified model were estimated using the spectral data and moisture data in the field. The result showed that the new indices have significant relationships with canopy water content . In particular, by implementing modified standardized for NDWI_{1 450}，NDWI_{1 940}，NDWI_{2 500.} The result indicated that newly developed indices with visible-infrared and shortwave infrared spectral feature may have greater advantage for estimation winter canopy water content.