基于不同灌溉条件下冠层光谱与参数的关系反演冬小麦冠层含水量

为监测冬小麦冠层含水量,根据TM5的波段响应函数,将不同灌溉条件下地面实测的冬小麦冠层窄波段光谱数据转化为TM5的宽波段反射率,计算了水分指数(NDWI和WI);同时,利用地面实测数据计算了冠层含水量(FMC和EWTc),并对水分指数和冠层含水量进行回归分析。结果表明,TM5的b7比b5波段在反演冬小麦冠层水分含量方面优势明显,NDWI比WI更具优势;利用最小二乘法建立了NDWI(b4,b7)与冬小麦冠层含水量的最佳拟合方程,反演FMC和EWTc的复相关系数分别为0.576 9和0.695 6;在此基础上,对河北保定部分地区的冬小麦冠层水分含量进行了空间填图,结果显示,研究区内冬小麦冠层水分含量具有西高东低的趋势,冬小麦生长旺盛的孕穗期冠层含水量比乳熟期高。

Inversion of winter wheat water content with the relationship between canopy parameters and spectra based on different irrigations

In order to monitor the canopy water content of winter wheat, canopy spectrums of winter wheat with narrow-band were resampled to broad-band according to relative spectral response (RSR) function of TM5. And then, normalized different water index (NDWI) and simple water index (WI) were calculated with broad-band reflectance. Fuel moisture content (FMC) and equivalent water thickness for canopy (EWTc) were got using dry weight, fresh weight and leaf area (index). The results show that b7 of TM5 is better than b5 in inversing canopy water content of winter wheat. Meanwhile, NDWI is more suitable than WI. Suitable fitting equations are built with NDWI (b4, b7) for FMC and EWTc, whose R2 reaches to 0.576 9 and 0.695 6, respectively. Finally, the spatial mapping of canopy water content is done with fitting equations. The results demonstrate that canopy water content of winter wheat is high in west and low in east in the studied area, and it's high in booting stage and low in milk stage.