Variability of particulate organic carbon in inland waters observed from MODIS Aqua imagery

LETTER • THE FOLLOWING ARTICLE IS OPEN ACCESS Variability of particulate organic carbon in inland waters observed from MODIS Aqua imagery Hongtao Duan1, Lian Feng2, Ronghua Ma1, Yuchao Zhang1 and Steven Arthur Loiselle3 Published 19 August 2014 • © 2014 IOP Publishing Ltd Environmental Research Letters, Volume 9, Number 8 Article PDF Figures References Citations PDF 2919 Total downloads Cited by 6 articles Article has an altmetric score of 1 Turn on MathJax Share this article Article information Abstract Surface concentrations of particulate organic carbon (POC) in shallow inland lakes were estimated using MODIS Aqua data. A power regression model of the direct empirical relationship between POC and the atmospherically Rayleigh-corrected MODIS product (Rrc,645-Rrc,1240)/(Rrc,859-Rrc,1240) was developed (R2 = 0.72, RMSE = 35.86 μgL−1, p < 0.0001, N = 47) and validated (RMSE = 44.46 μgL−1, N = 16) with field data from 56 lakes in the Middle and Lower reaches of the Yangtze River, China. This algorithm was applied to an 11 year series of MODIS data to determine the spatial and temporal distribution of POC in a wide range of lakes with different trophic and optical properties. The results indicate that there is a general increase in minimum POC concentrations in lakes from middle to lower reaches of the Yangtze River. The temporal dynamics of springtime POC in smaller lakes were found to be influenced by local meteorological conditions, in particular precipitation and wind speed, while larger lakes were found to be more sensitive to air temperature

Optimización del monitoreo de la transparencia del agua, por medio de MOD09GA: un caso de estudio en el lago Guamués, San juan de Pasto, Colombia

Lake Guamués (LG) has been considered a Ramsar Wetland since 2000. Due to its importance, lenttic ecosystems such as LG require monitoring programs that exceed their spatial and temporal scope. This study shows that using surface reflectance products, generated by the Modis sensor, can be useful in verifying the spatial dynamics of the Secchi disk depth (ZSD), in the 2001-2020 period. To calibrate the model, an image matching the field work performed was used. The transparency data of the Secchi disk-measured water column was correlated with the image pixels captured in the band centered at 858.5 nm. To validate the model, the Leave Out One Cross Validation (LOOCV) method was used. Thus, it was determined that the quadratic model showed better results with an adjustment in its R2 = 0.74 and an error associated with observations less than 0.013 m. Spatial analysis revealed that LG has areas located at its banks, where the ZSD may be less than 0.5 m. Likewise, its ZSD average in the image taken on April 24 is 3.87 m. The temporal analysis of the lake indicates that between the 2006-2008 and 2017-2020 periods, greater variability has been reported for the observed points, with values of 3.3 and 2.8 m, respectively.El lago Guamués (LG) es considerado humedal Ramsar desde el 2000. Debido a su importancia, los ecosistemas lénticos como el LG requieren de programas de monitoreo que sobrepasen su cobertura espacial y temporal. En este estudio se demuestra que usar productos de reflectancia de superficie, generados por el sensor Modis, puede ser útil para verificar la dinámica espaciotemporal de la profundidad medida con el disco de Secchi (PDS), en el periodo 2001-2020. Para calibrar el modelo, se utilizó una imagen coincidente con los trabajos de campo realizados; se correlacionaron los datos de transparencia de la columna de agua medida con el disco de Secchi con los píxeles de la imagen captados en la banda centrada en los 858,5 nm. Para validar el modelo, se utilizó el método Leave out One Cross Validation (LOOCV). Así, se determinó que el modelo cuadrático presenta mejores resultados con un ajuste en su R2 = 0,74 y un error asociado a las observaciones inferior a los 0,013 m. El análisis espacial reveló que el LG presenta zonas localizadas en sus márgenes donde la PDS puede ser inferior a los 0,5 m. De la misma forma el promedio en su PDS para la imagen del 24 de abril es de 3,87 m. El análisis temporal del lago indica que en 2006-2008 y 2017-2020, se ha presentado mayor variabilidad para los puntos observados, con valores de 3,3 y 2,8 m, respectivamente

A semi-analytical algorithm for deriving the particle size distribution slope of turbid inland water based on OLCI data: A case study in Lake Hongze

The particle size distribution (PSD) slope (ξ) can indicate the predominant particle size, material composition, and inherent optical properties (IOPs) of inland waters. However, few semi-analytical methods have been proposed for deriving ξ from the surface remote sensing reflectance due to the variable optical state of inland waters. A semi-analytical algorithm was developed for inland waters having a wide range of turbidity and ξ in this study. Application of the proposed model to Ocean and Land Color Instrument (OLCI) imagery of the water body resulted in several important observations: (1) the proposed algorithm (754 nm and 779 nm combination) was capable of retrieving ξ with R2 being 0.72 (p < 0.01, n = 60), and MAPE and RMSE being 4.37% and 0.22 (n = 30) respectively; (2) the ξ in HZL was lower in summer than other seasons during the period considered, this variation was driven by the phenological cycle of algae and the runoff caused by rainfall; (3) the band optimization proposed in this study is important for calculating the particle backscattering slope (η) and deriving ξ because it is feasible for both algae dominant and sediment governed turbid inland lakes. These observations help improve our understanding of the relationship between IOPs and ξ, which are affected by different bio-optic processes and algal phenology in the lake environment

Determination of the downwelling diffuse attenuation coefficient of lakewater with the sentinel-3A OLCI

The Ocean and Land Color Imager (OLCI) on the Sentinel-3A satellite, which was launched by the European Space Agency in 2016, is a new-generation water color sensor with a spatial resolution of 300 m and 21 bands in the range of 400-1020 nm. The OLCI is important to the expansion of remote sensing monitoring of inland waters using water color satellite data. In this study, we developed a dual band ratio algorithm for the downwelling diffuse attenuation coefficient at 490 nm (Kd(490)) for the waters of Lake Taihu, a large shallow lake in China, based on data measured during seven surveys conducted between 2008 and 2017 in combination with Sentinel-3A-OLCI data. The results show that: (1) Compared to the available Kd(490) estimation algorithms, the dual band ratio (681 nm/560 nm and 754 nm/560 nm) algorithm developed in this study had a higher estimation accuracy (N = 26, coefficient of determination (R2) = 0.81, root-mean-square error (RMSE) = 0.99m-1and mean absolute percentage error (MAPE) = 19.55%) and validation accuracy (N = 14, R2= 0.83, RMSE = 1.06 m-1and MAPE = 27.30%), making it more suitable for turbid inland waters; (2) A comparison of the OLCI Kd(490) product and a similar Moderate Resolution Imaging Spectroradiometer (MODIS) product reveals a high consistency between the OLCI and MODIS products in terms of the spatial distribution of Kd(490). However, the OLCI product has a smoother spatial distribution and finer textural characteristics than the MODIS product and contains notably higher-quality data; (3) The Kd(490) values for Lake Taihu exhibit notable spatial and temporal variations. Kd(490) is higher in seasons with relatively high wind speeds and in open waters that are prone to wind- and wave-induced sediment resuspension. Finally, the Sentinel-3A-OLCI has a higher spatial resolution and is equipped with a relatively wide dynamic range of spectral bands suitable for inland waters. The Sentinel-3B satellite will be launched soon and, together with the Sentinel-3A satellite, will form a two-satellite network with the ability to make observations twice every three days. This satellite network will have a wider range of application and play an important role in the monitoring of inland waters with complex optical properties