scholarly journals Bio-Optical Characteristics of the Black Sea Coastal Waters near Sevastopol: Assessment of the MODIS and VIIRS Products Accuracy

2021 ◽  
Vol 37 (2) ◽  
Author(s):  
E. Yu. Skorokhod ◽  
T. Ya. Churilova ◽  
T. V. Efimova ◽  
N. A. Moiseeva ◽  
V. V. Suslin ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Black Sea ◽  
Coastal Waters ◽  
Light Absorption ◽  
Ecological Monitoring ◽  
Optically Active ◽  
The Black Sea ◽  
Active Components ◽  
Chlorophyll A Concentration

Purpose. The purpose of the work is to evaluate accuracy of the satellite products for the coastal waters near Sevastopol, reconstructed by the standard algorithms based on the MODIS and VIIRS (installed at the artificial Earth satellites Aqua and Terra, and at Suomi NPP, respectively) data. Methods and Results. In situ sampling was carried out at the station (44°37'26" N and 33°26'05" E) located at a distance of two miles from the Sevastopol Bay. The chlorophyll a concentration was measured by the spectrophotometric method. The spectral light absorption coefficients by optically active components were measured in accordance with the current NASA protocol. The spectroradiometers MODIS and VIIRS Level 2 data with spatial resolution 1 km in nadir around the in situ station (44°37'26"±0°00'32" N and 33°26'05"±0°00'54" E) were used. The satellite products were processed by the SeaDAS 7.5.3 software developed in NASA. The research showed that the standard NASA algorithms being applied to the MODIS and VIIRS data, yielded incorrect values of the optically active components’ content in the Black Sea coastal waters near Sevastopol as compared to the data of in situ measurements in the same region: the satellite-derived “chlorophyll a concentration” was on average 1.6 times lower in spring, and 1.4 times higher in summer; the contribution of phytoplankton pigments to total light absorption at 443 nm was underestimated in 8.7 times; the light absorption by colored detrital organic matter was overestimated in 2.2 times. Conclusions. The NASA standard algorithms are inapplicable to calculating bio-optical indices in the coastal waters of the Black Sea near Sevastopol since they provide incorrect values of the satellite products (Ca-s, aph-s(443) and aCDM-s(443)). Operative ecological monitoring based on satellite data requires development of a regional algorithm taking into account the seawater optical features in the region and in the coastal zone, in particular.

scholarly journals Bio-Optical Characteristics of the Black Sea Coastal Waters near Sevastopol: Assessment of the MODIS and VIIRS Products Accuracy

2021 ◽  
Vol 28 (2) ◽  
Author(s):  
E. Yu. Skorokhod ◽  
T. Ya. Churilova ◽  
T. V. Efimova ◽  
N. A. Moiseeva ◽  
V. V. Suslin ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Black Sea ◽  
Coastal Waters ◽  
Light Absorption ◽  
Ecological Monitoring ◽  
Optically Active ◽  
The Black Sea ◽  
Active Components ◽  
Chlorophyll A Concentration

Purpose. The purpose of the work is to evaluate accuracy of the satellite products for the coastal waters near Sevastopol, generated by the standard algorithms based on the MODIS and VIIRS (installed at the artificial Earth satellites Aqua and Terra, and at Suomi NPP, respectively) data. Methods and Results. In situ sampling was carried out at the station (44°37’26" N and 33°26’05" E) located at a distance of two miles from the Sevastopol Bay. The chlorophyll a concentration was measured by the spectrophotometric method. The spectral light absorption coefficients by optically active components were measured in accordance with the current NASA protocol. The spectroradiometers MODIS and VIIRS Level-2 data with spatial resolution 1 km in nadir around the in situ station (44°37’26"±0°00’32" N and 33°26’05"±0°00’54" E) were used. The satellite products were processed by the SeaDAS 7.5.3 software developed in NASA. The research showed that the standard NASA algorithms being applied to the MODIS and VIIRS data, yielded incorrect values of the optically active components’ content in the Black Sea coastal waters near Sevastopol as compared to the data of in situ measurements in the same region: the satellite-derived “chlorophyll a concentration” was on average 1.6 times lower in spring, and 1.4 times higher in summer; the contribution of phytoplankton to total light absorption at 443 nm was underestimated in 8.7 times; the light absorption by colored detrital matter was overestimated in 2.2 times. Conclusions. The NASA standard algorithms are inapplicable to calculating bio-optical indices in the coastal waters of the Black Sea near Sevastopol since they provide incorrect values of the satellite products (Ca-s, aph-s(443) and aCDM-s(443)). Operative ecological monitoring based on satellite data requires development of a regional algorithm taking into account the seawater optical features in the region and in the coastal zone, in particular.

scholarly journals Vertical Distribution of Bio-Optical Properties of the Azov – Black Sea Basin Waters in April – May, 2019

2020 ◽  
Vol 27 (5) ◽  
Author(s):  
T. V. Efimova ◽  
T. Ya. Churilova ◽  
E. Yu. Skorokhod ◽  
N. A. Moiseeva ◽  
E. A. Zemlianskaia ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Light Absorption ◽  
Euphotic Zone ◽  
Optically Active ◽  
Colored Dissolved Organic Matter ◽  
Active Components ◽  
Absorption Coefficients ◽  
Chlorophyll A Concentration ◽  
Water Region ◽  
Total Light

Purpose. The work is aimed at investigating spatial distribution of the chlorophyll a concentration and the spectral light absorption coefficients by all optically active components in the Azov and Black seas in spring, when the seawater hydrophysical structure changes. Methods and Results. The data collected in the 106th scientific cruise of R/V Professor Vodyanitsky in April 19 – May 10, 2019 were used. The chlorophyll a concentration was measured by the spectrophotometric method. The spectral light absorption coefficients were determined in accordance with the NASA protocol 2018. The optical measurements were performed using the dual-beam spectrophotometer Lambda 35 (PerkinElmer). It was shown that in the surface layer of the Black Sea, the chlorophyll a concentration varied from 0.21 to 1.2 mg/m3. At some stations in the deep-water region, the increased values of this parameter were observed in the lower part of the euphotic zone that was associated with the beginning of seasonal water stratification due to the surface water heating. At these stations, the phytoplankton absorption spectra were more smoothed in the lower part of the euphotic zone than those in the upper layer. In the deep-water region, the non-algal particles contribution to the total particulate light absorption at wavelength 438 nm changed with depth from 40 ± 15 % at the surface to 29 ± 12 % near the bottom of the euphotic zone; whereas in the coastal waters this parameter was almost unchangeable within the water column (54 ± 11 %). No significant change of the colored dissolved organic matter contribution to the total light absorption with depth was revealed (69% on average). In the Sea of Azov, vertical distribution both of the chlorophyll a concentration (6.2 mg/m3 on average) and the spectral light absorption coefficients by all the optically active components was uniform. The non-algal particles contribution to the particulate light absorption was 40 ± 14 %, and the colored dissolved organic matter contribution to the total light absorption constituted 52 ± 6 %. Conclusions. New data on spatial distribution of the chlorophyll a concentration and the spectral light absorption coefficients by the optically active components in the Black and Azov seas were obtained for the spring period when the seawater hydrophysical characteristics changed.

scholarly journals Comparison of chlorophyll a concentration values retrieved from MODIS-Aqua spectroradiometer with the results of measurements in the coastal waters of the Black Sea near Sevastopol

2019 ◽  
Vol 4 (4) ◽  
pp. 53-61
Author(s):  
E. Yu. Skorokhod ◽  
T. V. Efimova ◽  
N. A. Moiseeva ◽  
E. A. Zemlianskaia ◽  
T. Ya. Churilova
Keyword(s):  
Chlorophyll A ◽  
Black Sea ◽  
Coastal Waters ◽  
Field Measurements ◽  
The Black Sea ◽  
Optical Monitoring ◽  
Chlorophyll A Concentration ◽  
Low Concentrations ◽  
Satellite Product ◽  
Significant Underestimation

The results of the comparison of the values of the standard satellite product “Chlorophyll a Concentration” recovered from MODIS-Aqua satellite with the results of field measurements in the coastal waters of the Black Sea near Sevastopol from 2009 to 2019 as a part of regular bio-optical monitoring have been presented. Differences between seasons in the nature of the error of the standard satellite product “Chlorophyll a Concentration” using the standard NASA algorithm were established: in spring, a significant underestimation of the values of the standard satellite product “Chlorophyll a Concentration” (up to 2.1 times) at high chlorophyll a concentrations was noted according to the results of the full-scale measurements, and in summer a significant overestimation of the values (up to 3.8 times) at low concentrations was noted. Throughout the year, depending on the season, the error in determining the standard satellite product “Chlorophyll a Concentration” on average varied from ±24 % to ±51 %. To increase the accuracy of determining the chlorophyll a concentration with remote sensing, it is necessary to use a regional approach.

scholarly journals Application of Satellite Data for Retrieving the Light Absorption Characteristics in the Black Sea Waters

2021 ◽  
Vol 28 (2) ◽  
Author(s):  
V. S. Suetin ◽  
S. N. Korolev ◽  
◽  
Keyword(s):  
Chlorophyll A ◽  
Black Sea ◽  
Satellite Data ◽  
Light Absorption ◽  
The Black Sea ◽  
Universal Method ◽  
Chlorophyll A Concentration ◽  
Inherent Optical Properties ◽  
Yellow Substance ◽  
The Crimea

Purpose. he work is aimed at studying the effects of light absorption in the Black Sea waters with due regard for the variations of its individual components, and how they are manifested in the NASA archival results of calculating the chlorophyll a concentration obtained by processing satellite data using the universal operational method. Methods and Results. The NASA archival data of the MODIS and SeaWiFS satellite instruments, and the values of the light absorption components (determined by the method of Generalized ocean color inversion model for retrieving marine inherent optical properties (GIOP)) related to yellow substance and phytoplankton were analyzed. In order to avoid possible manifestations of various distortions in the results of determining the remote sensing reflectance of the sea and in the products resulted from application of the GIOP method, only the specially selected and sufficiently reliable test data from two areas located near the Crimea Southern Coast and south of the Danube estuary were used. Conclusions. In the considered examples with low content of chlorophyll a in the seawater, the yellow substance plays a predominant role in light absorption in the spectrum blue part, whereas if the chlorophyll a content is high, the phytoplankton contribution is dominant. The revealed relationship between the light absorption components related to yellow substance and phytoplankton significantly differs from that implicitly preset as a basis of the universal method (applied in NASA for the satellite data operational processing) for determining the chlorophyll a concentration. This, in its turn, is manifested in the fact that the data on the chlorophyll a concentration in the Black Sea stored in the NASA archive may be overestimated in case the chlorophyll a concentration is low, and underestimated – in case it is high.

scholarly journals Development of phytoplankton in the winter-spring period in the coastal waters of Crimea

2021 ◽  
Vol 6 (1) ◽  
pp. 102-114
Author(s):  
Z. Z. Finenko ◽  
I. M. Mansurova ◽  
I. V. Kovalyova ◽  
E. Yu. Georgieva
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Chlorophyll A ◽  
Black Sea ◽  
Coastal Waters ◽  
Specific Growth ◽  
Shelf Zone ◽  
The Black Sea ◽  
Chlorophyll A Concentration ◽  
Spring Period

The analysis of phytoplankton in the winter-spring period is important for investigating peculiarities of its annual dynamics and the Black Sea ecosystem overall functioning. Phytoplankton state in the winter-spring period in the Black Sea shelf zone is less studied than that of the summer-autumn season; conducting such a research is especially important for solving several problems, related to the productivity of the last links of the food chain, the formation of water hydrochemical regime, and the carbon cycle in the sea. The aim of the work is to assess the effect of seasonal conditions on the development of phytoplankton and its production estimates in the winter-spring period in the coastal waters of Crimea. The article presents the results of studies of hydrophysical (water temperature, density, and relative transparency) and biological indicators (chlorophyll a concentration, its fluorescence, taxonomic composition, and phytoplankton production estimates) in the Black Sea shelf zone in January – April 2016–2019. The studies were carried out at 50 stations, located in the coastal waters of Crimea from the Karkinitsky Bay to the Kerch Strait. Chlorophyll a concentration was measured by the standard fluorometric method, species composition was determined by microscopy, and phytoplankton specific growth rate was calculated according to the previously developed model. In winter (January – February), the values of chlorophyll a content and upper mixed layer depth were the highest (0.42–0.52 mg·m−3 and 44–58 m, respectively); in spring (March – April) they were 2–3 times lower. In January – February, the coccolithophore species Emiliania huxleyi (Lohmann) W. W. Hay & H. P. Mohler, 1967 predominated; in March – April, in different years, either dinoflagellates and diatoms or coccolithophores, dinoflagellates, and diatoms prevailed. In winter, chlorophyll a vertical distribution at most stations was uniform; in spring, unimodal profiles with a depth maximum prevailed, the location of which was not related to temperature and density gradients. Relative changes in chlorophyll a concentration and fluorescence with depth were usually the same. Phytoplankton production and daily production/biomass ratio (P/B) increased from winter to spring. There was no correlation between the values of integral production, biomass, and maximum specific growth rate of algae. Maximum specific growth rate was the least variable indicator. During the winter-spring period, algae in the photosynthetic zone divided on average once every 2–5 days.

scholarly journals Application of Satellite Data for Retrieving the Light Absorption Characteristics in the Black Sea Waters

2021 ◽  
Vol 37 (2) ◽  
Author(s):  
V. S. Suetin ◽  
S. N. Korolev ◽  
◽  
Keyword(s):  
Chlorophyll A ◽  
Black Sea ◽  
Satellite Data ◽  
Light Absorption ◽  
The Black Sea ◽  
Universal Method ◽  
Chlorophyll A Concentration ◽  
Inherent Optical Properties ◽  
Yellow Substance ◽  
The Crimea

Purpose. The work is aimed at studying the effects of light absorption in the Black Sea waters with due regard for the variations of its individual components, and how they are manifested in the NASA archival results of calculating the chlorophyll a concentration obtained by processing satellite data using the universal operational method. Methods and Results. The NASA archival data of the MODIS and SeaWiFS satellite instruments, and the values of the light absorption components (determined by the method of Generalized ocean color inversion model for retrieving marine inherent optical properties (GIOP)) related to yellow substance and phytoplankton were analyzed. In order to avoid possible manifestations of various distortions in the results of determining the remote sensing reflectances of the sea and in the products resulted from application of the GIOP method, only the specially selected and sufficiently reliable test data from two areas located near the Crimea Southern Coast and south of the Danube estuary were used. Conclusions. In the considered examples with low content of chlorophyll a in the seawater, the yellow substance plays a predominant role in light absorption in the spectrum blue part, whereas if the chlorophyll a content is high, the phytoplankton contribution is dominant. The revealed relationship between the light absorption components related to yellow substance and phytoplankton significantly differs from that implicitly preset as a basis of the universal method (applied in NASA for the satellite data operational processing) for determining the chlorophyll a concentration. This, in its turn, is manifested in the fact that the data on the chlorophyll a concentration in the Black Sea stored in the NASA archive may be overestimated in case the chlorophyll a concentration is low, and underestimated – in case it is high.

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