Remote sensing retrieval of chlorophyll-a concentration based on normalized peak area in red band region

Due to the overlap of absorption and scattering of water constituents of case 2 waters, the retrieval precision of chlorophyll-a concentration is challenging. In this article, the absorption coefficient and backscattering coefficient of waters with different chlorophyll-a concentration were calculated after the absorption and back-scattering coefficients of special water constituents were measured. Afterwards, the above-water reflectance of remote sensing was achieved according to the radiation transfer model and the light-field distribution function of interface between the water and atmosphere. Based on the spectral characteristics of chlorophyll-a in red band region, two absorption boughs (Rrs₆₇₄ and Rrs₇₄₀) adjacent to reflectance peak were used to calculate the normalized peak area (NPA). After the relationship between the NPA and the chlorophyll-a concentration was studied, we concluded that there was a better relationship (R²=0.99) and lower RMS error (RMSE=5.09μg·L^-1) than other retrieval models of chlorophyll-a. The retrieval model of NPA (C = a × NPA^b + c, where C is the concentration of water constituents; a, b and c are the empirical parameters) has a promising prospect and could be used to retrieve the concentrations of water constituents with higher precision in accordance with the characteristics of various water constituents at different bands.