Deriving Total Suspended Matter Concentration from the Near-Infrared-Based Inherent Optical Properties over Turbid Waters: A Case Study in Lake Taihu

Wei Shi,Yunlin Zhang,Menghua Wang

doi:10.3390/rs10020333

Abstract

Normalized water-leaving radiance spectra nLw(λ), particle backscattering coefficients bbp(λ) in the near-infrared (NIR) wavelengths, and total suspended matter (TSM) concentrations over turbid waters are analytically correlated. To demonstrate the use of bbp(λ) in the NIR wavelengths in coastal and inland waters, we used in situ optics and TSM data to develop two TSM algorithms from measurements of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP) using backscattering coefficients at the two NIR bands bbp(745) and bbp(862) for Lake Taihu. The correlation coefficients between the modeled TSM concentrations from bbp(745) and bbp(862) and the in situ TSM are 0.93 and 0.92, respectively. A different in situ dataset acquired between 2012 and 2016 for Lake Taihu was used to validate the performance of the NIR TSM algorithms for VIIRS-SNPP observations. TSM concentrations derived from VIIRS-SNPP observations with these two NIR bbp(λ)-based TSM algorithms matched well with in situ TSM concentrations in Lake Taihu between 2012 and 2016. The normalized root mean square errors (NRMSEs) for the two NIR algorithms are 0.234 and 0.226, respectively. The two NIR-based TSM algorithms are used to compute the satellite-derived TSM concentrations to study the seasonal and interannual variability of the TSM concentration in Lake Taihu between 2012 and 2016. In fact, the NIR-based TSM algorithms are analytically based with minimal in situ data to tune the coefficients. They are not sensitive to the possible nLw(λ) saturation in the visible bands for highly turbid waters, and have the potential to be used for estimation of TSM concentrations in turbid waters with similar NIR nLw(λ) spectra as those in Lake Taihu.

Highlights

Total suspended matter (TSM) is an important biogeochemical parameter for both the ocean environment and inland waters
We further demonstrate that the NIR-based backscattering coefficients derived from the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP) can be used to accurately compute TSM concentrations due to the intrinsic
Using the in situ nLw(λ) at the NIR 745 and 862 nm and the corresponding TSM concentrations collected in various experimental investigations in 2006 and 2007 before the VIIRS-SNPP launch, two TSM algorithms were developed in Equation (2) with the least-square fitting approach

Summary

Introduction

Total suspended matter (TSM) is an important biogeochemical parameter for both the ocean environment and inland waters It can significantly impact the light fields in the water column, and affect water optical and biological properties, such as the diffuse attenuation coefficient at the wavelength of 490 nm Kd(490) [1,2,3], chlorophyll-a (Chl-a) concentration [4,5,6], and primary production [7,8], etc. Tassan [20] computed TSM using remote sensing reflectance at wavelengths of 488, 555, and 645 nm from Landsat Thematic Mapper (TM) data, and it was further tuned for MODIS observations in the Yellow Sea and East China Sea [21]. Other TSM algorithms, which are empirically tuned with different statistical approaches, were developed for the Yellow Sea and East China Sea [22,23]

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