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A hybrid method to estimate suspended particle sizes from satellite measurements over B ohai S ea and Y ellow S ea
Author(s) -
Sun Deyong,
Qiu Zhongfeng,
Hu Chuanmin,
Wang Shengqiang,
Wang Lin,
Zheng Lufei,
Peng Tian,
He Yijun
Publication year - 2016
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2016jc011949
Subject(s) - range (aeronautics) , particle size , moderate resolution imaging spectroradiometer , environmental science , particle size distribution , mass concentration (chemistry) , particle (ecology) , remote sensing , physics , satellite , computational physics , mineralogy , chemistry , materials science , geology , thermodynamics , oceanography , composite material , astronomy
Particle‐size distribution (PSD), a measure of particle concentrations at different sizes, is of great importance to the understanding of many biogeochemical processes in coastal marine ecosystems. Here, a hybrid method, including analytical, semianalytical, and empirical steps, is developed to estimate PSD through the median diameter of suspended particles (D v 50). Four cruise surveys were conducted to measure optical scattering properties, particle concentrations, spectral reflectance, and particle‐size distributions (obtained with a LISST instrument covering a size range of 2.5–500 μm) in coastal waters of Bohai Sea, Yellow Sea, and Jiangsu coastal region. Based on the Mie scattering theory,D v 50is closely related to mass‐specific backscattering coefficient of suspended particles (b bp *), and their relationship is calibrated through a power model ( R 2 = 0.796, n = 67, p < 0.001) for theD v 50range of 23.5–379.8 μm. The model is shown to perform better than the previously used inverse‐proportion model. The retrieval ofb bp *is through a bio‐optical model that links remote sensing reflectance just beneath the surface to inherent optical properties, where a close empirical relationship is established between particulate backscattering and particle concentration. The hybrid method shows high degree of fitting ( R 2 = 0.875, n = 46, p < 0.001) between the measured and estimatedD v 50for the size range of 17.2–325.2 μm used in the model calibration, while validation using two independent data sets shows mean absolute percentage errors of 46.0% and 64.7%, respectively. Application of the hybrid method to MODIS (Moderate Resolution Imaging Spectroradiometer) data results in spatial distributions ofD v 50that are generally consistent with those from in situ observations, suggesting potential use of the method in studying particle dynamics through time series of remote sensing observations. However, its general applicability to other regions still requires further research.