Wind and cloud cover effects on spectral measurements of flooded rice crops in red and near-infrared SPOT-HRV bands

Wind and cloud cover effects on variabilities of radiance, irradiance and reflectance were analysed using ground-based measurements acquired over flooded rice crops in the red and near-infrared SPOT-HRV bands under variable wind and cloud cover conditions. Overall, spectral measurements were more variable in the near-infrared than in the red band. Wind speed was positively correlated to variability of radiances (r=0.186 (p>0.001)) and reflectances (r= 0.245 (p>0.001)) in near-infrared, but not in red wavelengths. The proportion of diffuse radiation in the total incident solar radiation was positively correlated to the radiance variability in red (r=0.086 (p>0.001)) and near-infrared (r=0.123 (p>0.001)) as well as to the irradiance variability in red (r=0.248 (p>0.001)) and near-infrared (r=0.243 (p>0.001)), but not to the reflectance variability. Such an analysis should be done every time ground spectral measurements are performed under variable weather conditions.