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Summary of Proposal OCE3024

TitleTerraSAR-X detection and characterization of surfactant films deployed in an inland water reservoir
Investigator da Silva, Jose - University of Porto, Geosciences, Environment and Spatial Planning
Team Member
Professor Ermakov, Stanislav - Institute of Applied Physics, Russian Academy of Sciences
Dr. Sergievskaya, Irina - Institute of Applied Physics, Russian Academy of Sciences
Dr. Kapustin, Igor - Institute of Applied Physics, Russian Academy of Sciences
Dr. Magalhaes, Jorge - University of Porto, Geosciences, Environment and Spatial Planning
SummaryField experiments on radar detection and characterization of film slicks with the synthetic aperture radar onboard TerraSAR-X and an X-band scatterometer that can operate from board a research vessel are planned. The experiments will be carried out with surfactant films of pre-determined physical parameters, namely surface tension and film elasticity, at low to moderate wind conditions and at different radar incidence angles. We will study the dependence of radar backscatter (image contrasts) within surface films on wind velocity/direction, film elasticity and SAR incidence angles, within the range of 20-40 degrees. Scatterometer contrasts will be obtained at incidence angles varied in the range of about 45 to 70 degrees, and are expected to be larger than SAR. Theoretical analysis of radar contrasts for low-to-moderate incidence angles will be carried out based on a hydrodynamic model of wind wave damping due to films and on a composite radar imaging model. The hydrodynamic model includes wave damping due to viscoelastic films, wind wave generation and a phenomenological term describing nonlinear limitation of the wind wave spectrum. The radar model takes into account Bragg scattering and specular scattering mechanisms, the latter being usually negligible compared to the Bragg mechanism at moderate incidence angles (larger than 30-35 degrees), but giving noticeable contribution to radar backscattering at smaller incidence angles, particularly for slicks where cm-scale ripples are strongly attenuated by films. Calculated radar contrasts in slicks will be compared with field experiments results and assessment of the accuracy of current theory (i.e. hydrodynamic and radar models) will be attempted. For correct analysis/interpretation of the radar data, a number of environmental parameters will be measured using IAP RAS instrumental facility (complex), which includes: original optical instruments for studying wind wave parameters, a Ka-band scatterometer, an ultrasonic anemometer, an acoustic current profiler “Workhorse Sentinel” 600 kHz, STD probe YSI 6600 with sensors of blue-green algae and turbidity. All this apparatus will be mounted onboard a small research vessel specially designed and manufactured at IAP RAS. These unique experiments can extend essentially our knowledge about film slicks, their nature and evolution in the environment, develop models of radar probing of surface films (including oil spills and biogenic films) and abilities of SAR to detect and characterize marine films.Measurements of the PIs studies of film slicks are funded by the Russian Foundation of Basic Research (RFBR) in the frame of current Projects 14-05-00876 (2014-2016, PI S.Ermakov), 15-45-02690 (2015-2017, PI S.Ermakov).These studies are also supported by FRBR Projects 15-45-02650, (2015-2017, PI I.Sergievskaya), and 15-05- (2015-2017, PI I. Kapustin).Da Silva is funded by the Portuguese Foundation of Science and Technology (FCT) under the plurianual scheme of the Interdisciplinary Centre of Marine and Environmental Research CIIMAR and the group of Coastal and Ocean Dynamics (COD), which benefits from high performance computational resources. Magalhaes is funded by FCT under a post-doc scholarship (SFRH/BPD/84420/2012).

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