A new approach for atmospheric correction of MODIS imagery in turbid coastal waters: a case study for the Pearl River Estuary

The algorithms for atmospheric correction (AC) of Moderate Resolution Imaging Spectroradiometer (MODIS) data may yield negative water-leaving radiances in highly turbid coastal waters along the Pearl River Estuary of China. This failure of AC can be attributed to the high reflectance from the suspended sediments in the near-infrared (NIR) bands, which results in an overestimate of the aerosol scattering and hence overcorrection in the visible bands. In this letter, a new shortwave infrared extrapolation (SWIRE) method is presented for Terra-MODIS data. The Rayleigh-corrected reflectances in the SWIR bands (1.24, 1.64, and 2.13 mu m) are used to determine an exponential function with respect to wavelength, which is used to correct the NIR bands (0.748 and 0.869 mu m) for sediment scattering and hence estimate the aerosol scattering reflectances in these bands. Then the Gordon and Wang AC approach is applied. The performance of this new SWIRE algorithm is demonstrated using two examples centred on the Pearl River Estuary, with the results showing that the new approach can improve the AC for these turbid waters.