@article{Tsapanou2020,

title = {Coupling Remote Sensing Data with in-situ Optical Measurements to estimate Suspended Particulate Matter under the Evros River Influence (North-East Aegean Sea, Greece)},

author = {A. Tsapanou and E.Oikonomou and P.G. Drakopoulos and S. Poulos and G. Sylaios},

url = {https://www.tandfonline.com/doi/full/10.1080/01431161.2019.1685713},

doi = {https://doi.org/10.1080/01431161.2019.1685713},

year  = {2020},

date = {2020-10-06},

journal = {International Journal of Remote Sensing},

volume = {41},

number = {6},

pages = {2062-2080},

keywords = {Aegean Sea, optical, remote sensing},

pubstate = {published},

tppubtype = {article}

}

@article{Tsapanou2018b,

title = {Evaluating Ocean-Color Algorithms to remotely sense the surface suspended particle matter in the northeast Aegean Sea},

author = {A. Tsapanou and E. Oikonomou and S. Poulos and P.G. Drakopoulos},

url = {https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10773/2326133/Evaluating-ocean-color-algorithms-to-remotely-sense-the-surface-suspended/10.1117/12.2326133.short?SSO=1},

doi = {https://doi.org/10.1117/12.2326133},

year  = {2018},

date = {2018-08-06},

journal = {Proceedings of SPIE},

volume = {10773},

abstract = {Oceanographic investigations have significantly benefited from multispectral satellite products that simplify monitoring in coastal regions thanks to their high spatial-temporal resolution. The surface Suspended Particulate Matter (SPM) is an important water quality parameter which can be derived from empirical or analytical algorithms by using the atmospherically-corrected remotely sensed reflectance Rrs(λ) retrieved from satellite imagery. In this study, in situ SPM and Rrs(λ) data were collected in the Gulf of Alexandroupolis, Northeastern Aegean Sea in Greece (Eastern Mediterranean Sea) during low discharge period (June 2016). We attempt to compute remotely sensed reflectance from Landsat OLI8 imagery, in order to quantify surface SPM concentrations via both a Semi-Analytical and a Multi-Band Empirical Algorithm. When comparing the satellite estimations against the field measurements, both algorithm approaches provide a non absolute correlation with in situ Rrs (~20-30 % offset). As a result, a generic semi-analytical equation for Alexandroupolis Gulf is developed, following algorithm calibration in low turbidity waters. The proposed algorithm can be then equally implemented to the new Sentinel-2A sensor, in order to assess its variations against Landsat 8 and to determine the applicability extend of our approach.},

note = {Greece},

keywords = {algorithm development, earth observing sensors, in situ remote sensing, landsat, reflectivity, remote sensing, satellite},

pubstate = {published},

tppubtype = {article}

}

@article{Karageorgis2017b,

title = {Particle characterization and composition in the NE Aegean Sea: Combining optical methods and biogeochemical parameters},

author = {A.P. Karageorgis and P.G. Drakopoulos and S. Psarra and K. Pagou and E. Krasakopoulou and A.C. Banks and E. Papathanassiou},

url = {https://www.sciencedirect.com/science/article/pii/S0278434317301486},

year  = {2017},

date = {2017-10-11},

journal = {Continental Shelf Research},

volume = {149},

pages = {96-111},

abstract = {The NE Aegean Sea constitutes a challenging sector of the world ocean in studying optical and biogeochemical properties and processes due to a dynamic frontal regime resulting from the continuous mixing of Black Sea waters (BSW) and waters of Levantine origin (LW), which are characterized by substantially different physical, chemical and biological properties. In the framework of Perseus and AegeanMarTech projects, inherent optical properties (IOPs; beam attenuation, optical backscattering, chlorophyll-α fluorescence), particle size, and discrete bottle data (particulate matter, particulate organic carbon, and chlorophyll-α concentrations) were measured during October 2013, March and July 2014. Black Sea water enters into the Aegean Sea through the Dardanelles and disperses to the west-northwest, as traced by characteristic salinity minima. The core of the BSW to the east of Lemnos Island was occasionally particle-enriched, showing maxima in cp, bbp, D50, PMC, POC, and TChl-α, the latter, however, detected primarily at sub-surface layers. Particle composition was chiefly organic, associated with phytoplanktonic communities (BSW and LW), heterotrophic planktonic organisms and detrital organic matter primarily originating in the BSW and forming aggregates often >100 µm in diameter. A discrepancy between particle and TChl-α abundance was observed, with cp local maxima occurring in surface waters (BSW) and TChl-α maxima in mid-waters (LW). This pattern was attributed to phytoplankton photo- acclimation with depth leading to increased cell- chlorophyll content deeper, not necessarily matched by a similar biomass increase, thus, using TChl-α as an absolute proxy for phytoplankton biomass may not be appropriate, when considering water bodies encompassing the entire euphotic zone. Primarily in surface waters, the in situ optically measured median particle diameter primarily corresponds to large particles/aggregates, contrary to the findings obtained by laboratory analysis of cell counts in discrete water samples; this inconsistency was attributed to the fragile nature of aggregates that usually break up during sample processing and other methodological issues. The particulate backscattering ratio as well as the estimated bulk particulate index of refraction revealed a 2-layer structure, with biogenic particles and organic detritus occupying the upper ~65 m of the water column, whereas deeper waters were enriched in lithogenic/organic particles resuspended from the seabed. Overall, the NE Aegean Sea is characterized by low particulate matter concentrations and low chlorophyll biomass during the sampling periods, exhibiting rather open-sea characteristics, reflected on all optical properties studied, as evidenced by their very low values and also by the POC:cp regression parameters. The present work contributes to a better understanding of bio-optical properties of the Aegean Sea, which by extension may improve regional satellite algorithms applied to retrieve chlorophyll-α concentration from space.},

keywords = {attenuation, MSFD Descriptor 5, particles, phytoplankton photo- acclimation, remote sensing, scattering},

pubstate = {published},

tppubtype = {article}

}

@article{Drakopoulos2015c,

title = {Estimating chlorophyll concentrations in the optically complex waters of the North Aegean Sea from field and satellite ocean colour measurements},

author = {P.G. Drakopoulos and A.C. Banks and G. Kakagiannis and A.P. Karageorgis and A. Lagaria and A. Papadopoulou and S. Psarra and N. Spyridakis and V. Zervakis},

url = {https://www.spiedigitallibrary.org/conference-proceedings-of-spie/9535/1/Estimating-chlorophyll-concentrations-in-the-optically-complex-waters-of-the/10.1117/12.2192571.short?SSO=1},

doi = {http://dx.doi.org/10.1117/12.2192571},

year  = {2015},

date = {2015-06-19},

journal = {Proceedings of SPIE},

volume = {9535},

abstract = {In the Aegean Sea and Eastern Mediterranean there are large discrepancies between in situ and satellite ocean colour derived chlorophyll concentrations. The quantity that is monitored by ocean colour satellites and that can be used in the estimation of chlorophyll concentration is the remote sensing reflectance, defined as the ratio of the water leaving spectral radiance to the downwelling spectral irradiance. It can be determined in the field, with either above or in-water radiance and irradiance measurements. The complex optical properties of the North-East Aegean Sea, including radiance and irradiance, were studied during the AegeanMarTech project. Chlorophyll concentration estimates were derived from simultaneous above and in-water radiometric measurements. These were validated against chlorophyll concentration field data and compared against concurrent MODIS data from which chlorophyll was derived using two simple empirical algorithms. It was found that the MedOC3 algorithm outperforms the operational OC3M-547 algorithm and produces the least bias when compared against HPLC derived in situ chlorophyll. It is concluded that the greatest uncertainty in the inversion arises due to CDOM absorption below the 488 nm band. The reflectance ratios indicated that there is always an excess of yellow matter present in the study area and the water type could not be characterized optically as ‘’typical open ocean” Case 1.},

keywords = {algorithm development, MODIS, ocean optics, reflectivity, remote sensing, satellites, water},

pubstate = {published},

tppubtype = {article}

}