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

Abstract

Normalized water-leaving radiance spectra nL w (λ), particle backscattering coefficients b bp (λ) in the near-infrared (NIR) wavelengths, and total suspended matter (TSM) concentrations over turbid waters are analytically correlated. To demonstrate the use of b bp (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 b bp (745) and b bp (862) for Lake Taihu. The correlation coefficients between the modeled TSM concentrations from b bp (745) and b bp (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 b bp (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 nL w (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 nL w (λ) spectra as those in Lake Taihu.

Inherent Optical Properties in Lake Taihu Derived from VIIRS Satellite Observations

“…The annual frequency of significant blooms was found to increase from the time period of 2000-2004 to 2006-2008 [6]. The total suspended matter (TSM) concentration can also be retrieved and evaluated in Lake Taihu with satellite observations [7,8]. The long-term variability of the TSM concentration in Lake Taihu was characterized and quantified [7].…”

“…The total suspended matter (TSM) concentration can also be retrieved and evaluated in Lake Taihu with satellite observations [7,8]. The long-term variability of the TSM concentration in Lake Taihu was characterized and quantified [7]. In recent years, the environment in Lake Taihu has been deteriorating significantly [9].…”

“…The backscattering spectra from the blue to near-infrared (NIR) wavelengths in Lake Taihu are flat [17]. In fact, they are highly related to the TSM concentrations [7,17,18]. Shi et al [7] show that TSM concentrations in Lake Taihu have significant spatial and temporal variability.…”

A blended inherent optical property algorithm for global satellite ocean color observations

“…In turbid and highly turbid waters, studies have shown that r rs ( λ ) loses its sensitivity with the change of suspended particles in the visible wavelengths (Shi and Wang , ; Shen et al ). Thus, it is necessary to retrieve ocean biological and biogeochemical properties such as chlorophyll a (Chl a ) concentration, water turbidity, total suspended matter (TSM), and so on, with the satellite measurements in the near‐infrared (NIR) wavelengths (Gitelson et al ; Dogliotti et al ; Shi et al ).…”

“…The NIR spectral reflectance feature in the estuary of the Yellow River and Ancient Yellow River is found to be notably different from that of the Yangtze River (Shi and Wang 2014). This makes the satellite ocean color measurements at the red, NIR, and SWIR bands extremely valuable in conducting atmospheric correction (Gordon and Wang 1994;Wang 2007;Wang and Shi 2007), which characterizes and quantifies water properties in coastal and inland waters such as Chl a concentration (Gitelson et al 2007), floating green algae blooms (Hu 2009;Shi and Wang 2009b), river plumes (Shi and Wang 2009c), TSM (Miller and Mckee 2004;Shen et al 2010b;Son and Wang 2012;Shi et al 2018), and the light diffuse attenuation coefficient at 490 nm (Wang et al 2009;Zhang et al 2012). It is also found that the spectral features of nL w (λ) at the red and NIR wavelengths are dynamic and regional dependent (Ruddick et al 2006;Doron et al 2011;Shi and Wang 2014).…”