Measurement and correction of atmospheric effects in O2-B and O2-A absorption bands in the context of sun-induced fluorescence remote sensing

摘要

Under sun-light illumination, the shape of the atmospheric oxygen bands (O₂-B, 687 nm and O₂-A, 760 nm) of the vegetation radiance is modified by chlorophyll fluorescence. However for far-range measurements, atmospheric effects also modify this shape. In this study, measurements in O₂-A and O₂-B absorption bands have been performed at different altitudes up to 3123 m over bare soil and wheat fields. It is observed that bands depth increase significantly with altitude. In O₂-B band, the total magnitude of variation is of the same order of magnitude as the change induced by vegetation fluorescence, while it is much greater in O₂-A band. We used MODTRAN 4 to correct measurements from these atmospheric effects and to retrieve ground level band depths. It is found that the variation of corrected band depth with altitude is greatly reduced. These results show that MODTRAN 4 can be used to account for atmospheric effects. We also showed that an accurate evaluation of the contribution of environment is needed to correct band depth from atmospheric effects, especially in the O₂-B band.