This paper discusses satellite data usage in monitoring the surface oil pollution in the off-shore oil-producing area "Oil Rocks" in the Caspian Sea. For this study, we examined satellite SAR and VIS data taken over the region of interest in 2017-2020. All in all, we analyzed 558 satellite images. First of all, we present some statistics on the detectability of natural oil showings in SAR and VIS data. We show that the frequency of reliable detection of natural oil showings in satellite images varies greatly and depends sufficiently on a sensor type and the season. We state that the seasonal variability in the detection rate of natural oil showings on the sea surface is most pronounced for the VIS data. We show statistics on individual sizes of oil patches and describe their seasonal and inter-annual variability. We also present statistics on the frequency of detecting oil patches in the Oil Rocks oil-producing area in SAR images depending on near-surface winds and ocean-atmosphere boundary layer conditions. We compare our new results with those obtained in our previous long-term satellite survey of the Caspian Sea and discuss the reliability of quantitative estimates of surfaced oil amounts based on the satellite images. Further, we depict a detailed map of the spatial distribution of oil slicks detected in satellite imagery taken over the oil-producing area and outline high-risk areas of the sea surface oil pollution and areas exposed to potential risks.
In this paper, we attempt to fill some gaps in the knowledge of the oil pollution pattern in the whole area of the Caspian Sea on the base of the remotely sensed data. We present the results of a long-term survey of the Caspian Sea by use of satellite SARs and multispectral sensors. Our primary attention is focused on the oil showings on the sea surface due to natural hydrocarbon emissions from the seabed. During our satellite survey, we discovered a previously unknown seep of petroleum hydrocarbons from the seabed in the shelf area of the Caspian Sea near the Cheleken Peninsula, which belongs administratively to Turkmenistan. We documented its source point as the persistent location of the origins of 379 oil slicks detected in satellite images taken over the area of interest. We also performed the precise estimation of the actual positions of two offshore seeps on the Iranian shelf near the Cape Sefid Rud on the base of 173 and 198 oil slicks correspondently. For these two regions of interest, we compare the release rates of the crude oil from the seabed to the sea surface. Further, we assess the detection rate of oil showings on the sea surface, depending on a sensor type and the season. We put together detailed maps of the sea surface oil pollution caused by natural hydrocarbons seepages on the seabed and determine areas of the high risks of sea surface oil pollution.
The results of multi-year satellite monitoring of ice cover in the Caspian Sea are presented. The basis of the study was remote sensing data in the optical range, such as Sentinel-2 MSI, Landsat-8 OLI, Landsat-7 ETM+, Terra/Aqua MODIS, as well as archival Landsat-5 TM data. Also, Sentinel-1 SAR-C and archival ERS-1/2 SAR and Envisat ASAR radar data were used. The main objectives of the study were: determination of areas occupied by ice, identification of trends in ice formation and clearing periods, their inter-annual variability. To solve the problem of determining the parameters of ice cover, we used the multisensory approach whenever possible, i.e. comprehensive integrated analysis of heterogeneous data. The analysis of a vast array of satellite data, differing in nature and spatial resolution, and ice mapping was carried out using the toolkit of the See the Sea (STS) information system developed at the Space Research Institute of the Russian Academy of Sciences (IKI RAS). STS enables working with multi-year archival data, conduct joint analysis of different satellite data together with hydrometeorological information. It was found that during the study period, from the 1998-1999 winter to the present time, the largest area of ice cover of over 90,000 sq. km was observed in the 2011/2012 winter period. Ice was observed even in the bays of the Southern Caspian. Another direction of research, the results of which are presented, is the identification of capabilities and limitations in the use of satellite data obtained in different ranges (radar and optical) and at different polarizations.
In this paper, we discuss applications of satellite remote sensing for detection and analysis of spatiotemporal characteristics of oil showings on the sea surface due to natural hydrocarbon seafloor seeps in deep waters of the southeastern Black Sea. The study is based on the data obtained in the course of a satellite survey of the study region. The study region includes two areas of the heaviest oil pollution of the Black Sea surface. These are the areas of natural seepages off the Georgian coast near the town of Poti as well as the shelf area off the eastern coast of Turkey near the town of Rize. Our main result is the discovery of significant seasonal variability in the spatial distribution of natural oil films affected by local winds and surface currents prevailing in given periods. Further, we show that meso- and sub-mesoscale processes significantly affect the drift of natural oil spills. In the case of moderate winds and weak currents, the influence of these processes on the oil spills drift becomes paramount. We found that in 10-15 percent of cases, the oil film gets involved in vortical motions after its emersion on the sea surface, which often radically changes the trajectory of the slick propagation. Risks of oil surface pollution due to natural hydrocarbon showing are assessed for the test areas.
The work studies submesoscale fronts (with characteristic transverse scales lower than the Rossby internal radius of deformation) in inland seas on the base of remote sensing data. We show that we can significantly broaden our insights into the physics and geography of small-scale fronts by employing satellite synthetic aperture radar (SAR). During our satellite survey of the Baltic Sea, we obtained many satellite images of the sea surface bearing imprints of fronts of different formation mechanisms and different spatial and temporal characteristics. First we develop a methodology for identifying various submesoscale front signatures in SAR images and list the most common features of front manifestations. We describe characteristic features associated with fronts of different nature which are not usually detectable by traditional observational data sources because of their small scale and because they are often masked by upper-level clouds. The main problem is to discriminate between signatures of fronts in the sea and those in the nearsurface layer of the atmosphere. We validated our interpretations of front features in SAR images via the combined analysis of data on the sea surface and marine atmosphere condition, sea surface temperature, and mesoscale water dynamics.
Results of satellite observations of the Southeastern Black Sea are presented. Our work is aimed to the development and enhancement of satellite remote sensing technics for monitoring of sea surface oil pollution caused by the natural seepages of hydrocarbons from the seabed. We showed that multi-sensor approach to the satellite remote sensing survey contributes to a more comprehensive interpretation of the data and helps in developing a better understanding of the sea surface film pollution pattern. By using high-resolution satellite data, we were able to get a clear picture of a spatial and temporal variability of surface oil films and to show that their geographical distribution correlates with geographical locations of natural hydrocarbon seeps in this region. We used SAR for the precise estimation of the actual seafloor source location. We investigated the effect of surface winds and currents on transport, spreading, evolution, and persistence of oil slicks on the sea surface. We further demonstrated the importance of the effects of dynamic and circulation processes and natural factors (current meandering, vortical activity, and wind patterns) on the trajectory and fate of the released oil. We put together detailed maps of the sea surface oil pollution caused by natural hydrocarbons showings from the sea bottom in the south-eastern of the Black Sea and outlined the regions of the heaviest pollution.
The results of multi-year satellite monitoring of ice conditions in the Kerch Strait connecting the Black and Azov Seas are discussed. The issue gained importance in view of the ongoing construction of the Crimean Bridge across the strait. Our monitoring has been based on the whole variety of available satellite data including visible and radar data over the past 17 years. Every year the Azov Sea becomes fully or partially covered by ice during the cold season. In severe winters, ice often is carried to the Kerch Strait and even the Black Sea. An analysis of ice drift hydrometeorological conditions is presented. The ice conditions of 2017 are under special consideration. Everyday satellite monitoring of the Kerch Strait, including the construction area of the Crimean Bridge, revealed ice formation and drift features on the way from the Azov Sea through the Kerch Strait as well as ice interaction with the piers of the main and technological bridges under construction. It was found that, even under strong northeast winds, ice can pass neither through the piers, nor via the widest shipway. At present, it is hard to discern the impacts of the two bridges on floating ice, nevertheless when the construction is over and the technological bridge is gone, by all appearances the main bridge will strongly affect ice conditions in the Kerch Strait. This perspective calls for continuous satellite monitoring of the area that is enabled by cutting-edge systems and technologies.
Results of satellite observations of surface manifestations of internal waves in the Caspian Sea are presented. Our work produced data on a spatial and temporal variability of internal waves of non-tidal origin via their surface manifestations. By using high-resolution satellite data, we were able to get a clear picture of generation, propagation and interaction of internal wave packets and significantly broadened our insights on the physics and geography of internal waves in the World Ocean. The large amount of the data available allowed us to make some generalizations and obtain statistically significant results on a spatial and temporal variability of various internal wave surface manifestations in satellite images. We discovered numerous diverse instances of internal wave manifestations in satellite images of the Caspian Sea. We further demonstrated that this observed diversity of internal wave behavior is due to a diversity of their generation mechanisms and indicates the complexity of the dynamic environment in the region. We put together a detailed map of spatial distribution of surface manifestations of the internal waves in the Caspian Sea. We revealed a seasonal and inter-annual variability of wave activity, identified main regions of the internal wave localization for each season and revealed causes of a spatial inhomogenity of internal wave packet manifestations. Possible factors leading to the generation of non-tidal internal waves are determined on the basis of joint analysis of available satellite remote sensing data of the sea surface in microwave, visible (VIS) and infra-red (IR) ranges complemented by contact measurements.
The results of long-term satellite survey of the aquatic area of the Caspian Sea are presented. The patterns of surface oil pollution of the Caspian Sea are described and analysed. It is demonstrated that surface oil pollution is often caused by natural causes, namely by natural hydrocarbon seepages and mud volcanoes activity on the sea bottom. A combined analysis of oil film signatures in satellite radar and optical imagery data is performed. Mapping of the main types of surface pollution of the Caspian Sea is performed and areas of the heaviest pollution are outlined and analysed. Dependence of radar signatures of sea surface oil patches on the wind/wave conditions is investigated. The large amount of the data available allowed us to make some generalizations and obtain statistically significant results on a spatial and temporal variability of various sea surface film manifestations in SAR images. The impact of dynamic and circulation processes and natural factors (current meandering, vortical activity, temperature and wind patterns) on spatial and temporal distributions and intensity of oil films is studied. The connection between manifestations of natural seepages and mud volcanoes and earthquake activity in South Caspian and adjacent areas is established.
The paper discusses the results of a research on the influence of various hydrometeorological factors on distribution of suspended matter carried by rivers into the sea. The research is based on remote sensing data received in different bands of electromagnetic spectrum. Suspended matter concentration and integral water turbidity were estimated based on data from MODIS, MERIS, ETM+, TM and OLI sensors. The study was performed for two regions with very different characteristics: the semi-enclosed Gulf of Gdańsk of the Baltic Sea and eastern part of the Black Sea. It is shown that the plume fraction with highest suspended matter concentration of the lowland River Vistula spreads primarily under the impact of wind. Low concentration plume fraction is driven by the longshore current. In case of extraordinary floods, turbid Vistula waters spread in the upper sea layer almost all over the Gulf. The situation in the eastern part of the Black Sea with its narrow shoal and abrupt shelf edge wherein flow highly turbid mountain rivers is quite different. Here, the dominating role is played by runoff. Its intensity determines both plume shape and dimensions. A strong easterly wind can change plume configuration, cause formation of jet-like plumes.
Radar manifestations of ship wakes in zones of phytoplankton bloom are discussed. It is shown that these signatures can be regarded as indicators of biogenic activity. The main data are satellite radar images. Satellite visible (VIS) and infrared (IR) satellite data are also analyzed. The large amount of the available data allowed us to make some generalizations and obtain statistically reliable results concerning spatial and temporal variability of certain type of ship wake manifestations in synthetic aperture radar (SAR) images of the sea surface. Traditional classification of surface ship wakes manifestations in satellite SAR images specifies distinct features such as a dark trailing centreline region (turbulent wake), narrow V-wakes aligned at some angle to the ship’s path (the Kelvin wake), and, sometimes, internal wave wakes generated under conditions of shallow stratification. Their characteristic lengths are reported to be up to tens of kilometers and they can last from tens of minutes up to one hour. Instances of radar signatures of the ship wakes dissimilar to the previously described were detected in radar images obtained in the course of a satellite monitoring campaign of the central and south-eastern Baltic. These ship wakes can be seen in satellite radar images as long bright strips of enhanced backscatter with characteristic length of up to several hundred kilometres lasting more than 5 hours. A hypothesis is put forward of the coherence of this type of ship wakes detected in sea surface radar imagery and areas of intensive biogenic activity under conditions of low near-surface winds. Statistics on their seasonal, spatial and year-to-year distribution are drawn. These results are compared with temporal and spatial variations in chlorophyll a concentration and intensity of phytoplankton bloom in the area of interest. Chlorophyll a concentration maps derived from satellite data are used, as well as those based on in situ measurements. The relation between occurrences of this type of ship wake manifestations and areas of algae blooms is established.
The functionality, the goals and the current state of the distributed information system “See the Sea” (STS) are presented and discussed. This system is designed for investigating various processes and phenomena in the ocean and marine atmosphere using different types of satellite remotely sensed data. The STS system provides researchers with the possibilities to deal with the satellite remote sensing data as well as with the result of its analysis. The key feature of STS is the ability to work simultaneously with satellite information of different types. STS provides tools for joint analysis of different types of satellite data, as well as data of ground meteorological stations, cartographic data etc. This paper gives an overview of the system and data processing use cases. Some example cases are described including processing and joint analysis of various satellite data. The data from different sensors (obtained by Envisat ASAR, Landsat-8 OLI, Landsat-7 ETM+, Landsat-5 TM, Terra/Aqua MODIS as well as Hyperion and HICO hyperspectral data) was analyzed jointly for differentiation between different types of coastal waters, and for reconstruction of suspended matter distribution in the test areas of the Azov and Black Seas.
Satellite radar (SAR) and visible band data from Envisat ASAR, ERS-2 SAR, Lansat-5,7,8 sensors were used to investigate internal waves (IWs) in the Black Sea. The three main areas of the Black Sea where surface manifestations of internal waves (SMIWs) were mostly observed are: the Danube Delta, Crimea Peninsula and the northeastern region near Novorossiysk. The main goal of our investigation was to define the mechanisms of IW generation in the non-tidal sea. In the first area, IWs are observed rather often due to surface intrusions of fresh waters of the Danube River. In contrast to usual soliton-like IW trains caused by river plumes, soliton trains near the Danuba Delta propagate in different directions and often subject to nonlinear interactions. The interrelation between location and orientation of IW trains and fresh water fronts is discussed. In the area off Crimea, in our opinion, IWs are generated mainly by upwelling relaxation and interaction between internal inertial waves and bottom topography features. SMIW in the northeastern part of the Black Sea are scarce, though IWs are regularly revealed by in-situ measurements. Field measurements were conducted in the northeastern part of the Black Sea from a small boat and from scientific sea platform near Crimea employing CTD probes, thermistor chain and Acoustic Doppler Current Profilers (ADCP). ADCP measurements allowed us to detect a number of IW trains. Their amplitudes were estimated to reach 5-8 m. Joint analysis of satellite SAR and subsatellite data gave an assessment of their typical wavelength at 90-100 m.
Satellite high-resolution radar data from Envisat ASAR, RADARSAT-2 and TerraSAR-X sensors are used for the detection and investigation of fine structure of currents and submesoscale eddies. The fine structure of sea currents is manifested in radar images as quasiperiodic slick strips of a horizontal scale from tens of meters to several kilometers.
The strips are typically elongated along the currents apparently indicating their jet character and intermittence. The focus is on filamentary slick bands involved into small scale vortical processes and allowing estimation of spatial
characteristics of submesoscale eddies based on their SAR signatures. Submesoscale or eddies with diameters of less than Rossby radius of deformation could hardly be investigated by traditional oceanographic means due to spontaneity of their appearance, nonstationarity and short lifetimes. Sources of their generation are still not well known. A large archive of satellite data accumulated during 1999-2011 over different parts of the Black, Baltic and Caspian Seas has been analyzed in order to search, systemize and reveal mechanisms of formation and evolution of small scale eddy structures in these areas. Atmospheric and hydrological fronts and current instability have been found to play a significant role in submesoscale eddies generation. Subsatellite measurements using acoustic Doppler profiler (ADCP) have been performed aimed at verification and adjustment of the results obtained based on satellite radar data. The formation and drift of a near-shore submesoscale anticyclonic eddies of 5-7 km in diameter were observed.
The main goal of this study is to derive information on parameters characterizing airflows over the sea surface, particularly downwind natural obstacles from the analysis of SAR imagery. A series of ERS-2 SAR images of the sea surface recorded over north-eastern part of the Black Sea near the Caucasus coast is considered. This set of radar data has been collected in various seasons during 4 years. Related meteorological data, weather and cloudiness maps are available. A distinctive feature of the region is the mountain ridge stretched along shore and having a complicated structure with multiple canyons opening to the sea. Depending on the airflow characteristics radar images of sea surface can bear imprints associated with convection, internal waves in atmosphere, air jets, mushroom-like flows, lee waves, vortices, etc. Radar image patterns are investigated in relation to airflow speed and direction, boundary layer
stratification and local topography.
Results of microwave sounding of ocean surface are discussed. The study is based upon the data from airborne two-polarisation side-looking Ku-band radar, satellite based ERS SAR and the 'ALMAZ' SAR. The paper is dedicated to the theory and practice of analysis of radar images of sea surface, obtained under unstable atmosphere, when ocean is warmer than near-surface air. In this case, the sea surface reveals wind field variations in the MABL caused by atmospheric convective processes, accompanied by air motions with mainly vertical direction. Changes in radar manifestations of convection signatures are connected with the degree of thermodynamic instability of the atmosphere. It is shown that radar images of ocean under unstable atmosphere provide the imprints of convective processes in forms prescribed by theory, but in natural conditions air circulation in cylinder- or cell-formed structures differs from the model ones. It is suggested that the detection and investigation of active ocean-atmosphere energy exchange should be based on the polarization differences of radar cross section, especially under low grazing angles. The 2D-correlation functions of VV and HH-polarized radar images are considered with the aim to establish a quantitative criterion for the identification and discrimination between stable, unstable and neutral ocean-atmosphere stratifications.
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.