In this work, we obtained the results of salinity recovery in the Sea of Azov for the 19-year period 2000–2018, obtained on the basis of a regression model using regional biooptical parameters according to MODIS-Terra/Aqua data. To analyzed the deviations of the average monthly values of the restored salinity relative to climatology for 1913–2018. The results of the estimating of average monthly salinity anomalies in the spring and summer seasons relative to the climatic fields of salinity in the maps. Based on the comparison of the average monthly values of the reconstructed and observed in situ salinity, conclusions are drawn about the feasibility of using a regression model obtained by direct averaging of regression coefficients. The most effective regional bio-optical parameter determined, in terms of the best correlation of reconstructed salinity versus in situ measurements.
The aim of this work is to analyze the average monthly salinity of the surface layer of the Sea of Azov according to in situ measurements in the period 1913–2018 and remote sensing measurements in the period 2015–2022. We used in situ data at 0–2 m depths, as well as SMAP V5 level 3 monthly average sea surface salinity data with better spatial resolution than similar remote sensing instruments Aquarius and SMOS (MIRAS). Using the example of the Sea of Azov, it is shown that for shallow and slightly saline water areas, the error in determining salinity from satellite measurements is 0.5–3 relative to in situ observations.
The light absorption spectra of an algologically pure culture of the diatom Chaetoceros curvisetus Cleve were obtained for various light conditions and cell concentrations, and their description was given from the point of view of their subsequent use for identification of diatoms based on the analysis of satellite information.
Based on the analysis of long-term measurements by bio-argo floats, characteristic features are described and quantitative characteristics of the distribution of the light backscattering coefficient by suspended particles in the upper 1000-meter layer of the Black Sea are obtained.
This work precedes the field experiment on Lake Teletskoye, which is scheduled for August 10-20, 2023. The main goal of the work is to get an information of the regional features and seasonal variability of the optically active characteristics of the water upper layer of Lake Teletskoye based on the Level-2 standard products of the OLCI optical scanner.
A three-band satellite algorithm for retrieval of the bio-optical properties of surface waters, developed for the Black Sea, was adapted to the waters of the Southern Ocean (Atlantic region) on the basis of spectral light absorption coefficients of all optically active components (phytoplankton, non-algal particles and coloured dissolved organic matter) measured during the scientific cruises RV “Akademic Msctislav Keldysh” in austral summer 2020 and 2022. The accuracy of the regional algorithm was estimated by comparison with the in situ data. The advantage of the regional algorithm in comparison with the standard one in the range of low values of bio-optical parameters of water was shown, and an approach to further refinement of the algorithm to ensure correct assessment in waters with a relatively high content of optically active components was discussed.
The use of satellite scanners of medium resolution to study inland water regions, such as lakes and large reservoirs, is an important task. In this paper, using the example of Lake Baikal, the limitations of the new HawkEye medium-resolution satellite scanner for studying the optical characteristics of lakes are identified and described. A technique for adaptation the regional algorithm for recovering the vertical light attenuation coefficient obtained for the OLCI bands ratio to the the HawkEye bands ratio is tested.
Using the results of the 4D IOPs model, an estimate of the lower boundary of the photosynthesis zone in the deep water region of the Black Sea was obtained. For the year warm period, its value significantly differs downward (by 5–10 m) from that obtained in earlier paper. At the cold period, this difference in estimates is smaller and amounts to 2–3 m. The main reason is the more correct consideration of the light absorption profile of dissolved organic matter, which increases with depth.
The paper discusses an approach to reconstructing the salinity fields of the Sea of the Azov based on obtaining generalized regression equations relating in situ archival data in 1913–2012. With regional biooptical parameters obtained from MODIS second level standard products. The possibility of prompt recovery of salinity fields in the surface layer of the sea and the use of the results of the proposed method in the construction of spatial maps of the Azov Sea salinity, synchronized in time with satellite images is show. The reliability of the obtained results is confirmed by a good agreement between the average values of the restored salinity and the long-term average salinity trends of the Sea of the Azov according to in situ data in the modern periods of 1986–2018 and 2000–2018.
The purpose of the work was to build a regional algorithm for reconstructing the vertical diffuse attenuation coefficient at 380, 443, 490, 510, 555, 590 and 620 nm for Lake Baikal based on quasi-synchronous in situ measurements and the standard ocean color Level-2 OLCI product. For the first time, the spatial distribution of the diffuse attenuation coefficient was obtained at seven wavelengths in the upper layer of Lake Baikal.
Based on the analysis of the Bio-Argo floats measurements for the backscattering coefficients by particles at 532 nm and 700 nm in the Black Sea waters and a regional ocean color product with the involvement of a physical model, the measurements of these parameters were corrected, the slope of the backscattering coefficients by particles was calculated, and its time function in the photic layer of the Black Sea was plotted.
The regional full spectral primary production model accuracy has been assessed based on the comparison results of calculation with the data of measurements of chlorophyll a concentration and primary production (gross) in the surface layer of the western and eastern regions of the sea in September and December curried out in the scientific cruises in the period from 2005 to 2016. The comparison showed a good agreement between measured and calculated primary production data. The assimilation number is considered as one of the criteria for the assessment of the accuracy of the primary production model.
A method based on the use of statistical models and mathematical procedures to obtain regular information on the temperature and salinity of the Sea of Azov in the form of maps of their vertical and surface distribution is proposed. We used the measurements of temperature and salinity for the period 1913–2012 and the observations data from MODIS-Aqua/Terra instruments regularly passing over the Sea of Azov, and the simulation results of three-dimensional hydrodynamic Princeton Ocean Model supplemented by mathematical procedures. The possibility of the operative recovery of salinity values is based on regression statistics on the bio-optical characteristics index34 = RRS(531)/RRS(488) and bbp(555). They are obtained from remote sensing observations and indicate the total absorption of light and its scattering by suspended particles in top layer of water.
Based on the field measurements of the light absorption spectra of phytoplankton pigments, the non-algal suspended matter, the colored dissolved organic matter and ocean color product, remote sensing reflectance, reconstructed from MODIS instruments from Aqua and Terra measurements, regression equations were obtained to restore the main biooptical characteristics in Sea of Azov: total concentration of chlorophyll a and pheopigments, coefficients of light absorption by phytoplankton pigments, non-living organic matter and coefficient of light backscattered by particles suspended at 438 nm. The daily 2D maps of these parameters were constructed in the surface layer from 2000 to 2018.
The profiles of the light attenuation coefficients, reconstructed using a model based on statistics of bio-argo floats and regional satellite product, as well as measured under natural conditions in the Black Sea, were compared. Additionally, we compared the values of the attenuation coefficient of photosynthetically active radiation – Kd(PAR), obtained on the basis of spectral measurements of horizontal irradiance, with the results of direct measurements of Kd(PAR) on the shelf and the deep-sea parts of the Black Sea. The effects of meteorological conditions, cloudiness on PAR attenuation in the upper and lower the sea layers are demonstrated.
The information capabilities of spectral measurements of underwater irradiance in the upper layer of Lake Baikal were demonstrated. It allowed to obtain the spectra of the vertical light attenuation coefficient, to restore the spectral structure of the incident solar radiation, including changes of photosynthetically active radiation with depth, and to calculate a number of primary bio-optical characteristics of water: spectra of the CDM absorption coefficient and the light backscattering coefficient, as well as the chlorophyll-a concentration.
A statistical analysis of profiles from 0 to 70 meters of potential temperature and main bio-optical characteristics of the Black Sea was performed: chlorophyll a concentration, particle backscattering coefficient at 700 nm, the concentration of the colored component of dissolved organic matter, obtained as a result of long-term measurements from three bio-argo floats. The analysis made it possible to describe the profiles of the above parameters, as well as their dynamics during the year. In comparison with the obtained profiles previously used in the model, calculations showed their higher accuracy. The last made it possible, in conjunction with satellite, measurements more accurately restore the vertical structure of the bio-optical characteristics of the upper layer of the Black Sea from September 1997 to December 2018.
In the paper a joint analysis of direct measurements of the seawater vertical diffuse attenuation coefficient with a satellite product was carried out for several stations on the northwestern shelf of the Black Sea in late April and early May 2017. An attempt to model the empirical spectrum of the seawater vertical diffuse attenuation revealed a number features of that were explained by the peculiarity of the vertical structure, namely, by the presence of an optically active layer, which is typical for the considered period of time and is associated with the thermocline formation process.
This paper provides a synergetic approach between numerical modeling and remote sensing of bio-optical water properties. The work demonstrates that appropriate data-assimilation schemes make numerical modeling a suitable and reliable tool for filling the gaps arising due to satellite imagery unavailability and/or cloud covering. In this research we apply the Princeton Ocean Model to the Sea of Azov, assimilating bio-optical indexes (index34 and bbp(555)) from MODIS L2 products. These data identify the presence of suspended matter (mineral suspended matter from river discharges or resuspending as a result of a strong wind), and suspended matter of biological origin. The ad hoc assimilation/correction scheme allows for prediction (and reanalysis) of transport and diffusion of the bio-optical tracers. Results focus on the ability of the method to provide spatial maps that overcome the general issues related to Ocean Color imagery (e.g., cloud cover) and on the comparison between the assimilating and the non-assimilating runs. Methods of joined information analysis are discussed and the quality of model forecasts is estimated depending on the intervals of the satellite data assimilation. Hydrodynamic modeling of the Sea of Azov was carried out for the period of 2013–2014 applying meteorological data of the regional weather forecasting system SKIRON/Eta. The analysis of data coherence helps to detect negative changes to the sea waters, predict them and forecast typical areas and territories subject to anthropogenic impact. The successive data-assimilation algorithm is proved to improve the forecast of suspended matter transfer.
Coefficient of diffuse attenuation coefficient for downwelling irradiance at wavelength 490 nm (Kd (490)), obtained from measurements of the MODIS device from the Aqua satellite and the effect of an absorbing aerosol on a standard satellite product was studied. For this the event of absorbing aerosol transfer over the Black Sea northwestern shelf area which was diagnosed at the AERONET-OC Gloria station in the summer season of 2014 was considered. It was shown that the presence of an absorbing aerosol in the atmosphere leads to an overestimation of the standard satellite product: Kd (490) in comparison with its value calculated from the ascending radiation spectrum direct measurements at the above-mentioned AERONET- OC.
For the first time light absorption by all optically active components (phytoplankton, non-algal particles and colored dissolved organic matter) has been measured in the Sea of Azov. Regional bio-optical properties have been shown for winter and spring seasons.
Seasonal and interannual dynamics of bioluminescence field (BF) generated by Dynophyta in the upper 60m depth layer was studied using the data of biophysical monitoring in the coastal zone near Sevastopol lasted from Jan 2009 till Dec 2014. In addition, satellite-derived sea surface temperature (SST) data and long-term standard measurements at the nearest meteorological station (30 years long) were used. From these datasets pronounced monthly SST anomalies were extracted. SST anomalies were shown to induce taxonomic restructuring of phytoplankton community and changes in the BF vertical structure.
The effect of errors related to the given optical properties inaccuracy of the atmosphere and the condition of the air-water boundary after atmospheric correction, and the error in ocean color product from the SeaWiFS and MODIS tools is considered.
Bio-optical studies were carried out in coastal waters around the Crimea peninsula in different seasons 2016. It was shown that variability of chlorophyll a concentration (Chl-a), light absorption by suspended particles (ap(λ)), phytoplankton pigments (aph(λ)), non-algal particles (aNAP(λ)) and by colored dissolved organic matter (aCDOM(λ)) in the Crimea coastal water was high (~order of magnitudes) in all seasons 2016. Relationships between ap(440), aph(440) and Chl-a were obtained and their seasonal differences were analyzed. Spectral distribution of aNAP(λ) and aCDOM(λ) were parameterized. Seasonality in aCDOM(λ) parameterization was revealed, but - in aNAP(λ) parameterization was not revealed. The budget of light absorption by aph(λ), aNAP(λ) и aCDOM(λ) at 440 nm was assessed and its seasonal dynamics was analyzed.
An precision of the chlorophyll-a concentration and the detrital matter absorption coefficient using different algorithms for the Black Sea are obtained on the basis of numerical experiments in which varied the depth of the optically active layers and the its albedo. The numerical experiments compared with satellite observations performed in the deepwater part of the Black Sea in the first half of summer 2000 during the intensive coccolithophorids blooms are in good agreement.
Vertical diffuse attenuation coefficient, Kd(490), is one of the key parameter required for water quality modeling, hydrodynamic and biological processes in the sea. We showed that standard level-2 product of Kd(490) was underestimated in comparison with Kd(490) values simulated by the regional model during the diatom bloom in the Black Sea. Using data of SeaWiFS, MERIS and MODIS color scanners, a regional relationship between the model value of Kd(490) and the ratio of remote sensing reflectances has been obtained. Based on the bulgarian argo-bio-buoy dataset, the relationship between the attenuation coefficient of photosynthetically active radiation and attenuation coefficient at a wavelength of 490 nm is obtained. The simplified model, below as the S-model, of the diffuse attenuation coefficient spectrum for downwelling irradiance in the Black Sea upper layer is described. As a consequence of the S-model, the link between the depth of the euphotic zone and Kd(490) has been obtained. It is shown that the Kd(490) values, retrieved from ocean color data with using the regional link and from argo-bio-buoy measurements at depths between 6-20 m, are close to each other.
In this study, a regional algorithm for retrieving Inherent Optical Properties (IOPs) has been developed for the Black Sea using remote sensing reflectance at five wavelengths in the visible spectral range corresponding to the Sea-viewing Wide Field of View Sensor (SeaWiFS). The model retrieves a spectral signature of particle backscattering coefficient at 555 nm, bbp(λ), and its spectral slope, np, total absorption coefficient of colored detrital matter (sum of colored dissolved matter and non-algal particles, CDM) at 490 nm, aCDM(λ), spectral slope of CDM absorption coefficient, S, and chlorophyll a concentration, Ca. These satellite derived set of IOPs and bio-optical properties measured in situ in the western open Black Sea within period 1998-1999 have been analyzed. The result reveals four specific cases corresponding to 1) variation of spectral slope of CDM absorption coefficient, 2) coccolithophores blooms, 3) domination of micro-celled phytoplankton (diatoms and/or dinoflagellates) and 4) presences of the picoplankton in phytoplankton community. Examples of the spatial distribution and seasonal variability of the retrieved parameters in half-monthly composite maps are presented. A complete set of these maps for SeaWiFS lifetime is available on http://blackseacolor.com/.
A statistical research by years and seasons of dust aerosol event from the Middle East over the Black Sea using the seven-day back trajectory analyses for the period since 2007 to 2015 was conducted. The main optical and microphysical characteristics of arid aerosol from the area of the Sahara and Syrian desert was obtained from the results of Cimel measurements on Sevastopol station of international network AERONET. The data submitted 1. on the website of the international AERONET network: trajectories transfer of BTA (Back Trajectory Analyses) at 8 levels of pressure; 2. satellites data; 3. HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory Model) model data for Sevastopol and other Black Sea stations have been analysed.
Long term (1996 – 2014) averaged annual dynamics of daily photosynthetically available radiation (PAR) incident on the surface of the Black Sea have been estimated for different degree of sky coverage by the cloudiness. To this aim PAR standard product of color scanners (OCTS, SeaWiFS, MODIS-Aqua/Terra) has been processed. The processing method was based on the assumption that temporal PAR dynamics over one day corresponded to PAR spatial variability in the Black Sea area scanned by satellite instruments during one overpass. PAR data could be applied for different researches of the Black Sea ecosystem, which is related to photo-physiological processes.
Since 1997 the U.S. satellite sensor SeaWiFS is providing an information, that can be helpful to monitor Black Sea
waters in routine operational mode. Due to the errors inherent in atmospheric correction procedures, the possibilities to
determine the full spectrum of normalized spectral water-leaving radiance are very limited. At the same time the analysis
shows that the use of two SeaWiFS channels at 510 and 555 nm allow us to detect many interesting features of temporal
and spatial variability of the effects of absorption and scattering of light in the Black Sea.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.