An Improved Land Target-Based Atmospheric Correction Method for Lake Taihu

Land target-based atmospheric correction methods over inland waters are an effective alternative method for when the standard or improved atmospheric correction method that is based on water is invalid. The type of aerosol model that is selected and land dark target that is distinguished are two key factors that could determine the atmospheric correction's accuracy. We present an improved land target-based iterative method [denoted as dense dark vegetation (DDV)-WC] for the atmospheric correction of Moderate Resolution Imaging Spectroradiometer (MODIS) over Lake Taihu. The improvements include the use of aerosol models in Optical Properties of Aerosols and Clouds (OPAC), which fully consider the impact of relative humidity (RH) on aerosol properties, and a rigorous land dark target selection rule (DDV-WC-Selection). The DDV-WC algorithm includes three steps: the selection of DDV pixels from lakeshore areas, the retrieval of the aerosol optical thickness (AOT) at 550 nm (AOT550) for the selected DDV pixels, and the retrieval of the remote sensing reflectance (Rrs) over water. The AOT550 inversion accuracy of different aerosol models in OPAC is tested in Lake Taihu. The "continental clean model" has the best performance compared with five other aerosol models for every month of the year. Therefore, the aerosol model of the DDV-WC algorithm is fixed to the "continental clean model" in Lake Taihu because of its stable and excellent performance. When using the " continental clean model" to perform these retrievals, the DDV pixels selection (DDV-WC-Selection) in the DDV-WC method (MRE(Mean Relative Error) = 14.63%) is more reliable than the DDV pixels selection (DDV-Selection) in the MODIS V5.2 method (MRE = 17.24%). The atmospheric correction of MODIS indicates that this approach produces superior performance in the green and red bands but poor results in the near-infrared (NIR) and blue bands. The MRE is only 13.15% at 645 nm. These findings illustrate that the DDV-WC algorithm is a practical MODIS atmospheric correction method for inland turbid waters.