Atmospheric Correction Algorithm for HY-1C CZI over Turbid Waters

Tong, C.; Mu, B.; Liu, R.-J.; Ding, J.; Zhang, M.W.; Xiao, Y-.F.; Liang, X.-J., and Chen, X.-Y., 2019. Atmospheric correction algorithm for HY-1C CZI over turbid waters. In: Jung, H.-S.; Lee, S.; Ryu, J.-H., and Cui, T. (eds.), Advances in Remote Sensing and Geoscience Information Systems of Coastal Environments. Journal of Coastal Research, Special Issue No. 90, pp. 156-163. Coconut Creek (Florida), ISSN 0749-0208.China's HY-1C ocean-observing satellite was launched successfully on September 7, 2018. It carries a four-channel wide-band coastal zone imager (CZI) that has 50 m spatial resolution and 950 km swath width. To exploit the potential of quantitative ocean color inversion, accurate atmospheric correction is needed. However, because of the CZI band settings, the realization of this goal is a challenge, especially for turbid water with complex optical properties. This study investigated the atmospheric correction algorithm for the CZI over turbid water. First, using the 6SV radiative transfer model, CZI Rayleigh lookup tables (LUTs) were built to correct for atmospheric molecular Rayleigh scattering, greatly shortening the time required for operational data processing. Second, CZI aerosol scattering was removed using the Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol LUTs and quasi-synchronous MODIS aerosol products. The accuracy of the CZI atmospheric correction was validated using data from the highly turbid Bohai Sea. In comparison with synchronous in situ data, the results showed the average relative error of CZI remote sensing reflectance (Rrs) in the blue, green and red bands was 32.51 %, 25.38 % and 42.10 %, respectively. Comparison of CZI Rrs with quasi-synchronous MODIS data revealed similar spatial distributions, although the spatial information from the CZI was more detailed. The results proved the validity and accuracy of the CZI atmospheric correction algorithm over turbid water, which lays a foundation for quantitative ocean color inversion with high spatial resolution in the coastal zone.