Iterative near-infrared atmospheric correction scheme for global coastal waters

Abstract

Atmospheric correction (AC) is a key step in ocean color remote sensing for obtaining oceanic and coastal water ecosystem products. However, traditional NIR-based AC scheme (ACNIR) often fails in turbid coastal waters dominated by high suspended particulate matter (SPM). SWIR-based AC is valid for turbid waters, but it cannot be applied to some satellite sensors (e.g., Sea-viewing Wide Field-of-view Sensor (SeaWiFS), MEdium Resolution Imaging Spectrometer (MERIS), and future small satellite sensors) that have no SWIR bands. To obtain reliable data of turbid coastal waters by these sensors without SWIR bands, an improved ACNIR (ACNIR-PRO) scheme is proposed herein based on the frame of traditional ACNIR (ACNIR-STA). The synthesized and in situ datasets are analyzed to extend bio-optical models of absorption and backscattering coefficients in ACNIR-STA to highly turbid waters. ACNIR-PRO utilizes concentrations of both chlorophyll-a ([Chla]) and SPM ([SPM]) to estimate water-leaving contributions at the NIR bands. Similar to NIR-SWIR AC, ACNIR-PRO can obtain the information of global coastal waters with remote sensing reflectance at 862 nm (Rrs(862)) up to 0.025∼0.03sr−1. Rrs of ACNIR-PRO is also validated by AERONET-OC datasets (mean absolute percent difference (MAPD) of Rrs(551) is approximately 16%) for various coastal waters including high colored dissolved organic matter. Further, the magnitude and spatial patterns of [SPM] and [Chla] derived from the Rrs products after performing ACNIR-PRO are significantly better than those from ACNIR-STA, especially for turbid coastal waters.