Mesoscale surface current fields in the Baltic Sea derived from multi-sensor satellite data

Gade, Martin; Seppke, Benjamin; Dreschler-Fischer, Leonie S.

doi:10.1080/01431161.2011.628711

Cited by 19 publications

(10 citation statements)

References 15 publications

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“…Another interesting oceanographic application of multichannel spaceborne SAR systems lies in the detection and mapping of biogenic and anthropogenic surface films, e.g., alga blooms or waste deposits. Several works showed that the drift of sea surface films can be measured from space using repeated and/or intersatellite image acquisitions with time lags of several minutes to hours and correlation techniques that enable to track patterns on the sea surface [24], [25]. Spaceborne bistatic SAR-ATI offers a new and effective way to image and map these phenomena with a single data acquisition.…”

Section: Detection and Mapping Of Surface Filmsmentioning

confidence: 99%

Ocean Surface Observations Using the TanDEM-X Satellite Formation

Suchandt

Runge

2015

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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The TanDEM-X SAR satellite formation permits improved ocean surface observations by means of bistatic alongtrack interferometry (ATI) when compared to single-satellite systems. The flexible imaging geometry of its two cooperating SAR sensors forms an interferometer that can achieve very high sensitivity to motions of objects on ground. This way, radar imaging of surface currents with unprecedented accuracy, high spatial resolution and wide coverage at the same time becomes possible. We demonstrate the capabilities of the sensor in the contexts of tidal current mapping, measurement of thermohaline and wind-driven ocean currents as well as detection of areas with surface films. We have developed a dedicated postprocessing system for TanDEM-X image products that allows extracting surface current information from the data. By this paper, we address bistatic data acquisition and processing aspects for sea surface imaging with TanDEM-X like interferometric baseline geometry, temporal decorrelation, and phase calibration. We present a variety of examples of data evaluation that clearly demonstrate the application potential of the methodology.Index Terms-Ocean surface currents, SAR along-track interferometry (ATI), TanDEM-X. working on numerous aspects of interferometric synthetic aperture radar (SAR) processing. He was engaged in data calibration, processor development, and digital elevation model processing of the Shuttle Radar Topography Mission (SRTM) and worked on the design and development of an automatic traffic information extraction system for TerraSAR-X data. He has a wide experience in SAR interferometry, ground moving-target indication, signal processing, and software development. Furthermore, he is currently responsible for the design of a SAR geodesy processing system. His research interests include ocean surface observations using multichannel spaceborne SAR.Hartmut Runge received the Dipl.-Ing. degree in communications technology from the University of Siegen, Siegen, Germany, in 1980. He is a DLR Staff Member and has been working with the first digital SAR processor and on various aspects of SAR processing and applications. He was one of the inventors of the basic chirp scaling algorithm and the responsible system engineer of the data processing chain for the X-SAR missions and the Shuttle Radar Topography Mission (SRTM). In that mission, he was also the Principal Investigator for the along-track interferometry experiments and used this technique to reveil the potential for ocean current measurements. His research interests include geodetic SAR applications.

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Section: Detection and Mapping Of Surface Filmsmentioning

confidence: 99%

Ocean Surface Observations Using the TanDEM-X Satellite Formation

Suchandt

Runge

2015

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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“…High spatial resolution imagery from satellites capable of along-track stereo, or from satellites that follow each other closely in time on similar orbits, can be exploited for target motion given appropriate time lags between the image acquisitions [1][2][3][4][5][6][7][8][9]. In the ocean, targets take the form of spatial gradients and other features in ocean color and surface temperature, suspended material, surface films, and (as in this work) algae.…”

Section: Introductionmentioning

confidence: 99%

“…In the ocean, targets take the form of spatial gradients and other features in ocean color and surface temperature, suspended material, surface films, and (as in this work) algae. Ocean currents can be deduced from time-lagged images by using various techniques such as maximum cross-correlation [2,4,8] and optical flow [4][5][6][7][8][9]. Particularly exciting is the possibility of using high-resolution time-lagged imagery to explore the realm of the ocean submesoscale, in which strong surface convergences and downwelling become associated with horizontal density fronts and cyclonic vortices e.g., References [10,11].…”

Section: Introductionmentioning

confidence: 99%

Use of WorldView-2 Along-Track Stereo Imagery to Probe a Baltic Sea Algal Spiral

Marmorino

Chen

2019

Remote Sensing

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The general topic here is the application of very high-resolution satellite imagery to the study of ocean phenomena having horizontal spatial scales of the order of 1 kilometer, which is the realm of the ocean submesoscale. The focus of the present study is the use of WorldView-2 along-track stereo imagery to probe a submesoscale feature in the Baltic Sea that consists of an apparent inward spiraling of surface aggregations of algae. In this case, a single pair of images is analyzed using an optical-flow velocity algorithm. Because such image data generally have a much lower dynamic range than in land applications, the impact of residual instrument noise (e.g., data striping) is more severe and requires attention; we use a simple scheme to reduce the impact of such noise. The results show that the spiral feature has at its core a cyclonic vortex, about 1 km in radius and having a vertical vorticity of about three times the Coriolis frequency. Analysis also reveals that an individual algal aggregation corresponds to a velocity front having both horizontal shear and convergence, while wind-accelerated clumps of surface algae can introduce fine-scale signatures into the velocity field. Overall, the analysis supports the interpretation of algal spirals as evidence of a submesoscale eddy and of algal aggregations as indicating areas of surface convergence.

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“…The tracking of sea surface slicks to derive sea surface velocities is not limited to a single type of spaceborne sensor. Gade et al [22] demonstrated such an application in the Baltic Sea with multiple satellite data from the thematic mapper, ERS-2 SAR, ENVISAT ASAR, wide-field scanner, and the Sea-Viewing Wide Field-of-View Sensor (SeaWIFS). The derived surface currents from the multiple satellite acquisitions are generally larger than those provided by the numerical models, whereas they present small-scale turbulent structures which are resolved by the operational models.…”

Section: Introductionmentioning

confidence: 99%

Derivation of Sea Surface Tidal Current From Spaceborne SAR Constellation Data

Ren

Gao³

et al. 2017

IEEE Trans. Geosci. Remote Sensing

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In this paper, we demonstrate an application of spaceborne synthetic aperture radar (SAR) constellation data to derive sea surface tidal current at high spatial resolution. The maximum cross correlation (MCC) method, which has been widely applied to optical remote sensing data to derive sea surface velocities, is applied to X-band SAR data from TerraSAR-X (TSX) and TanDEM-X (TDX), which were operating in pursuit monostatic mode. Because of the short temporal interval of TSX and TDX's pursuit acquisitions, temporal decorrelation is minimized to derive tidal current fields that exhibit significant temporal and spatial variations. In addition, we combined data from TDX and another X-band SAR, COSMO-SkyMed, to obtain a virtual SAR constellation data pair, which was also analyzed using the MCC method to derive the tidal current field. Case studies of Hangzhou Bay in the East China Sea and Amrum Island in the North Sea are presented. The SAR-derived tidal current fields were compared to the results of numerical model simulations, high-frequency (HF) radar measurements and in situ measurements. MCC coefficients that are greater than 0.8 are an appropriate threshold for the further derivation of tidal currents. Comparisons to finite volume community ocean model, HF radar and general estuarine transport model results yield root-mean-square errors of 0.13, 0.06, and 0.05 m/s, respectively. Measurements from three field stations were also compared to the MCC SAR retrievals, yielding differences of 0.3, 0.07, and −0.09 m/s. Index Terms-Maximum cross correlation (MCC), tidal current field retrieval, X-band synthetic aperture radar (SAR) constellation.

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Mesoscale surface current fields in the Baltic Sea derived from multi-sensor satellite data

Cited by 19 publications

References 15 publications

Ocean Surface Observations Using the TanDEM-X Satellite Formation

Ocean Surface Observations Using the TanDEM-X Satellite Formation

Use of WorldView-2 Along-Track Stereo Imagery to Probe a Baltic Sea Algal Spiral

Derivation of Sea Surface Tidal Current From Spaceborne SAR Constellation Data

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