Dynamic Sea Surface Research Articles

Influence of mesoscale eddies on wind retrieval from C-band synthetic aperture radar images

ABSTRACT Synthetic Aperture Radar (SAR) is an innovative technique for monitoring sea surface dynamics and has a large swath coverage (>200 km). In this paper, we investigate the characteristics of anticyclonic and cyclonic eddies on SAR and the influence of mesoscale eddies on SAR wind retrieval. Mesoscale eddies in the global oceans are identified from daily sea level anomaly (SLA) data in 2022–2023, which are integrated by the Haiyang-2B/2C/2D (HY-2B/2C/2D) altimeters. A total of 1000 Sentinel-1 (S-1) images acquired in interferometric-wide (IW) and extra-wide (EW) modes are available, and they cover the mesoscale eddies. In addition, swath wind products from HY-2 scatterometers and sea surface temperature (SST) data from Haiyang-1C (HY-1C) are collected. Co-polarized (vertical–vertical (VV) and horizontal–horizontal (HH)) Geophysical Model Function (GMF) C-SARMOD2 was applied to invert the wind speed with reference to the scatterometer-measured wind direction. The variation in the difference (SAR retrievals minus scatterometer measurements) indicates that the SST of below 11°C has a certain impact on the SAR wind retrieval. The influence is weak at higher SSTs, and the difference increases with increasing eddy kinetic energy (EKE). It is concluded that the shear current associated with mesoscale eddies is a significant factor that affects the accuracy of SAR-derived winds.

An affordable operational oil spill monitoring system in action: A diachronic multiplatform analysis of recent incidents in the southern Gulf of Mexico

The coexistence of marine sensitive areas with the oil industry requires robust preparedness and rapid response capabilities for monitoring and mitigating oil spill events. Scientifically proven satellite-based methods for the visual detection of oil spills are widely recognized as effective, low-cost, transferable, scalable, and operational solutions, particularly in developing economies. Following meticulous design and implementation, we adopted and executed a relatively low-cost operational monitoring and alert system for oil spill detection over the ocean surface and alert issuance. We analyzed over 1500 satellite images, issuing over 70 warning reports on oil slicks and spills in the southern Gulf of Mexico. To assess the system’s efficiency and performance, we leveraged data from three major oil spill incidents in the study region during June and July of 2023 in the study region, covering a maximum area of 669 km2 and tracked for 12 to 24 days. We documented the evolution of these oil spills by integrating satellite sensing data with on-site Lagrangian drifting buoys, a network of high-frequency radars, and citizen reports to validate the outcomes of this system. We generated timely technical information on the spill’s evolution, informing decision-makers and local community leaders to strengthen their mitigation response capabilities. Additionally, we developed a robust database with spectral and spatiotemporal features of satellite-detected oil, thereby contributing to advancing the scientific understanding of sea surface dynamics related to natural and anthropogenic oil sources. This study also highlights immediate-, medium-, and long-term research agendas and establishes a reference for a sustained, transferable, and operational oil spill monitoring system.

Sea state contributions to thermosteric sea-level in high-resolution ocean-wave coupled simulations

This study examines the impact of wave-induced processes (WIPs) in modulating thermosteric sea-level changes, highlighting the need to include these processes in future sea-level rise assessments and climate projections. The impact of wave-induced processes on thermosteric sea-level changes is investigated using coupled ocean-wave simulations. These simulations include the effects of Stokes-Coriolis forcing, sea-state dependent surface stress and energy fluxes, and wave-induced mixing. The experiments use a high-resolution configuration of the Geesthacht COAstal Model SysTem (GCOAST), covering the Northeast Atlantic, the North Sea and the Baltic Sea. The GCOAST system uses the Nucleus for European Modelling of the Ocean (NEMO) ocean model to account for wave-ocean interactions and ocean circulation. It is fully coupled with the WAM spectral wind wave model. The aim is to accurately quantify the sea state contribution to thermosteric sea level variability and trends over a 26-year period (1992–2017). The ability of wave-ocean coupled simulations to reveal the contribution of sea state to sea level variability and surge is demonstrated. It is clear that wave-induced processes (WIPs) play a significant role in sea surface dynamics, ocean mixing (mixed layer thickness) and modulation of air-sea fluxes (e.g. heat flux) in both winter (10–20%) and summer (10%), which in turn affect thermosteric sea level variability. The North Atlantic (in summer) and the Norwegian Trench (in winter) show significant contributions (40%) to the thermosteric sea-level variability due to wave-induced processes. The influence of WIPs on thermosteric sea level trends in the North Atlantic is up to the order of 1 mm yr-1 in both winter and summer, in the open ocean and at the shelf break. Smaller contributions are observed over the shelf areas of the North Sea. This study underscores the crucial role of WIPs in modulating sea-level changes and highlights the importance of including these processes in future sea-level rise assessments and climate projections.

Improving Ocean Management Using Insights from Space.

Advancements in space-based ocean observation and computational data processing techniques have demonstrated transformative value for managing living resources, biodiversity, and ecosystems of the ocean. We synthesize advancements in leveraging satellite-derived insights to better understand and manage fishing, an emerging revolution of marine industrialization, ocean hazards, sea surface dynamics, benthic ecosystems, wildlife via electronic tracking, and direct observations of ocean megafauna. We consider how diverse space-based data sources can be better coupled to modernize and improve ocean management. We also highlight examples of how data from space can be developed into tools that can aid marine decision-makers managing subjects from whales to algae. Thoughtful and prospective engagement with such technologies from those inside and outside the marine remote sensing community is, however, essential to ensure that these tools meet their full potential to strengthen the effectiveness of ocean management.

Influence of sea surface waves on numerical modeling of an oil spill: Revisit of symphony wheel accident

The greatest purpose of this study is to analyze the importance of surface waves on the hindcasting of the oil spill through the Symphony wheel accident in the Qingdao coastal waters. During the accident period, a total of four synthetic aperture radar (SAR) images by Gaofen-3 (GF-3) were acquired from 2 to 19 May 2021. The hindcasting of two sea surface dynamics, namely currents and waves, is carried out using a coupled marine numeric model. This model, known as the finite-volume community ocean model-simulating waves nearshore (FVCOM-SWAVE), employs a triangular grid. Simulated significant wave height (SWH) is validated against remotely sensed product by the Haiyang-2B (HY-2B) altimeter on April 2021 yields a root mean square error (RMSE) of 0.38, a correlation coefficient (COR) of 0.78, and a scatter index (SI) of 0.34. Subsequently, Stokes drift estimated by waves are included to hindcasting oil spills using the oil particle-tracing method. The bias of the spatial coverage (SAR minus simulations) of an algorithm called the constant false alarm rate (CFAR) is −73.92 km2 with Stokes drift, which is significantly less than the 55.45 km2 coverage without Stokes drift. Moreover, compared with model-simulated oil spills, the bias of the geographic location at the center point with Stokes drift is 8.18 km, which is less than the 12.95 km bias without Stokes drift. These results demonstrate that Stokes drift needs to be included in the prediction of oil spills.

Underwater acoustic propagation and scattering from a dynamic rough sea surface using the Finite-Difference Time-Domain method.

Models for underwater acoustic propagation typically assume that the sea surface is smooth or rough but frozen in time. Long-duration transmissions on the order of tens of seconds are being considered for next-generation SONAR. These types of signals improve target resolution and tracking. However, they can interact with the sea surface at many different wave displacements during transmission. This violates the "frozen" boundary assumption and causes additional transmission losses and Doppler effects on the received signal. Full-wave propagation models can be used to better understand the mechanisms behind these phenomena. This understanding leads to better system design without having to perform expensive at-sea experiments. In this paper, a finite-difference time-domain (FDTD) method is implemented to model the impact of roughness and motion on the sea surface. The FDTD method is a full-wave numeric technique that allows an arbitrary function to define the boundary points. Surface motion is accomplished by modifying these boundary points at each time step. A variable subgrid sea surface boundary technique is developed to improve the accuracy of these FDTD simulations. The rough, time-evolving sea surface is modeled using a Pierson-Moskowitz frequency spectrum, which is simple to implement and fully defined by wind speed and direction.

Training Neural Mapping Schemes for Satellite Altimetry With Simulation Data

AbstractSatellite altimetry combined with data assimilation and optimal interpolation schemes have deeply renewed our ability to monitor sea surface dynamics. Recently, deep learning schemes have emerged as appealing solutions to address space‐time interpolation problems. However, the training of state‐of‐the‐art neural schemes on real‐world case‐studies is hindered by the sparse space‐time coverage of the sea surface of real altimetry data set. Here, we introduce an innovative approach that leverages state‐of‐the‐art ocean models to train simulation‐based neural schemes for the mapping of sea surface height and demonstrate their performance on real altimetry data sets. We analyze further how the ocean simulation data set used during the training phase impacts this performance. This experimental analysis covers both the resolution from eddy‐present configurations to eddy‐rich ones, forced simulations versus reanalyzes using data assimilation and tide‐free versus tide‐resolving simulations. Our benchmarking framework focuses on a Gulf Stream region for a realistic 5‐altimeter constellation using NEMO ocean simulations and 4DVarNet mapping schemes. All simulation‐based 4DVarNets outperform the operational observation‐driven and reanalysis products, namely DUACS and GLORYS. The more realistic the ocean simulation data set used during the training phase, the better the mapping. The best 4DVarNet mapping was trained from an eddy‐rich and tide‐free simulation data sets. It improves the resolved longitudinal scale from 151 km for DUACS and 241 km for GLORYS to 98 km and reduces the root mean square error by 23% and 61%. These results open research avenues for new synergies between ocean modeling and ocean observation using learning‐based approaches.

Simulation of the reflection of a high energy laser beam at the sea surface for hazard and risk analyses

The application of a high energy laser beam in a maritime scenario necessitates a laser safety concept to prevent injury to personnel or uninvolved third parties from uncontrolled reflections of laser light from the sea surface. Therefore, it is crucial to have knowledge of the amount and direction of reflected laser energy, which varies statistically and depends largely on the dynamics of the wavy sea surface. These dynamics are primarily influenced by wind speed, wind direction, and fetch. An analytical model is presented for calculating the time-averaged spatial intensity distribution of the laser beam reflected at the dynamic sea surface. The model also identifies the hazard areas inside which laser intensities exceed a fixed exposure limit. Furthermore, as far as we know, our model is unique in its ability to calculate the probabilities of potentially eye-damaging glints for arbitrary observer positions, taking into account the slope statistics of gravity waves. This is a critical first step toward an extensive risk analysis. The simulation results are presented on a hemisphere of observer positions with fixed radii from the laser spot center. The advantage of the analytical model over our numeric (dynamic) model is its fast computation time. A comparison of the results of our new analytical model with those of the previous numerical model is presented.

Surface water mass dynamics at IODP Site U1313 through Principal Component Analysis: Evidence from coccolith assemblages in the ∼25–7 kyr interval

Coccolith assemblages from Integrated Ocean Drilling Program Site U1313 (North Atlantic; 41°0′N, 32°57.4′W) are analysed to assess temporal changes in surface water conditions from the Last Glacial Maximum (LGM) to the Middle Holocene (∼25–7 kyr). We perform Principal Component Analysis (PCA), involving both calcareous nannofossil assemblage data and other paleoenvironmental proxies. We reconstruct sea-surface dynamics using calcareous nannofossil assemblage variations and comparison with other previously published proxy data from Site U1313 including C37:4 alkenone, dolomite/calcite and quartz/calcite ratios, Uk’37 SST, as well as the sedimentation rate.We use variations in paleoproductivity proxies, cold and warm water group abundance, and the PCA results to infer North Atlantic Current (NAC) and North Atlantic Transitional Waters (NATW) migration through the studied interval. These proxies are also used to highlight variations in the Subtropical Gyre dynamics. Warming episodes are recorded during the LGM and Heinrich Stadial (HS) 1 as a result of northward expansion of the Subtropical Gyre. High coccolithophore productivity episodes characterize HS 1 and 2, and are concomitant with increasing terrigenous input. Both processes are considered a consequence of iceberg influence, which transport nutrients and ice-rafted debris to the area. A southward shift of the Subpolar Front and NAC favour the expansion of cold water from 25.3 ka to the end of the Younger Dryas, whereas the early Holocene is characterized by NATW influence resulting from northward migration of the NAC and Azores Current.

A novel and computationally efficient subgrid technique for modeling scattering and Doppler effects of rough dynamic sea surfaces using the finite-difference time-domain method

Over the last decade, the improvements in computational performance that multiprocessing, solid-state hard drives, and fast memories have brought to desktop workstations have made modeling and simulation methods that were previously inaccessible into the office workspace. These methods were previously restricted to large servers or computer clusters because of their demanding computation and large memory requirements when applied to underwater acoustic simulation scenarios. One such method is the Finite-difference Time-domain (FDTD) technique. The FDTD method is a discrete numeric model that provides the full pressure wave solution solved directly in the time domain. This makes it an ideal model for investigating scattering and Doppler effects of boundaries with complex geometries and motion. A fully developed sea surface generated using the Pierson–Moskowitz wavenumber spectra meets these criteria. A novel subgrid technique has been developed to improve the accuracy of signals scattered from fully developed sea surfaces. This method remains computationally efficient because the subgrid is applied only along the rough sea surface as it varies over time. The FDTD subgrid method has been applied to simulations that investigate the “frozen” sea surface assumption that is utilized by other traditional models that incorporate boundary motion.

Bottom‐Current Variability and the Relationship With Topography and Sedimentary Processes in the Drake Passage

AbstractBottom‐current related sediments have been commonly used for paleoceanographic reconstructions. However, the strength and variability of bottom currents are poorly understood and thus the processes that control sedimentation in deep environments are not clear. In this study, we focus on the Drake Passage, which is connected to the Antarctic Circumpolar Current, that has a major impact on the global climate. We studied the intensity and variability of bottom currents and how they are related to sedimentary processes. For this purpose, we used 27‐years from GLORYS12 Mercator Ocean reanalysis at high resolution to evaluate the bottom current dynamics. Geophysical data and surface grain size measurements were used to identify the type of sediment deposits. Our results show that the dynamics of bottom currents is disconnected from the sea surface dynamics, and bottom circulation is strongly controlled by the rough topography of the Drake Passage. The patterns for the first modes of bottom‐current variability are related to the local topography and seem to generally control the distribution of contourites. The second and third EOF modes show patterns in the bottom currents that differ from the mean field, and they may affect the rate of erosion and deposition differently. Time series of bottom currents reveals multiple high‐speed current events, but contourite drifts seem to accumulate preferentially in zones of slow and stable bottom currents. Our study highlights the potential of using ocean reanalysis to better constrain bottom currents in zones of scarce data and to plan future campaigns of direct measurements.

Analysis of Sea Surface Dynamics during the Coastal Floods in Manado

Coastal flooding is one of the serious problems facing most coastal areas in the world. On January 17 and December 7, 2021, coastal flooding hit the coastal area of Manado, North Sulawesi, Indonesia. The disaster disrupted economic activities on the coast of Manado Bay. This study analyzed the dynamics of the atmosphere and the sea during coastal flood events using water level data from the Geospatial Information Agency, which was then filtered to separate residual and atmospheric tide, and oceanographic reanalysis data of Wavewatch-III from BMKG Ocean Forecast System (OFS). The results show that events on January 17 and December 7, 2021, coincided with the occurrence of the maximum tide. The residual water level shows a significant value of around 0.2 – 0.3 m, indicating the influence of atmospheric phenomena on sea level rise. According to oceanographical data, the local wind is the main factor of flood occurrence, which is shown by wind speed data which increased wave height significantly to 1,5 m on January 17, 2021, and to 2,0 m on December 7, 2021, around Manado Bay coast. Another factor that might contribute to the event is Manado's land morphology. Further study must be conducted to discover the influence of land morphology on coastal floods.
 Keywords: Coastal flood; Water level; Tide
 
 
 Copyright (c) 2023 Geosfera Indonesia and Department of Geography Education, University of Jember
 This work is licensed under a Creative Commons Attribution-Share A like 4.0 International License

Improved Analytical Formula for the SAR Doppler Centroid Estimation Standard Deviation for a Dynamic Sea Surface

The existing formulas for the synthetic aperture radar (SAR) Doppler centroid estimation standard deviation (STD) suffer from various limitations, especially for a dynamic sea surface. In this study, we derive an improved version of these formulas through three steps. First, by considering the ocean wavenumber spectrum information, a new strategy for determining the number of independent samples of the sea wave velocity field is adopted in the new formula. This is contrary to the method used in the existing formulas, where the number of SAR geometric resolution cells is taken as the number of samples assuming that adjacent SAR resolution cells are statistically uncorrelated. Second, the pulse repetition frequency and Doppler bandwidth are decoupled in the new formula, unlike in the existing formulas where they are unchangeably related to each other. Third, the effects of thermal noise and Doppler aliasing are jointly quantified in a mathematically exact manner instead of being treated separately, as in the existing formulas. Comprehensive SAR raw data simulations for the ocean surface show that the new formula has a better performance in predicting the Doppler centroid estimation STD than the existing formulas.

Refining the Resolution of DUACS Along-Track Level-3 Sea Level Altimetry Products

This paper describes the demonstration of a regional high-resolution level-3 (L3) altimeter data unification and altimeter combination system (DUACS) developed with support from the French space agency (CNES). Deduced from full-rate (20 Hz to 40 Hz) level-2 (L2) altimeter measurements, this product provides sea level anomalies (SLA) and other essential physical variables at a spatial resolution of one sample every ~1 km over the North Atlantic Ocean. This allows us to resolve wavelengths from ~35 km to ~55 km depending on the altimeter considered. This was made possible by recent advances in radar altimeter processing for both synthetic aperture radar (SAR) and low-resolution-mode (LRM) measurements, as well as improvements made to different stages of the DUACS processing chain. Firstly, the new adaptive and low-resolution with range migration correction (LR-RMC) processing techniques were considered for Jason and Sentinel-3 (S3A), respectively. They significantly reduce errors at short wavelengths, and the adaptive processing also reduces possible land contamination near the coast. Next, up-to-date geophysical and environmental corrections were selected for this production. This includes specific corrections intended to reduce the measurement noise on LRM measurements and thus enhance the observability at short wavelengths. Compared with the 1 Hz product, the observable wavelengths reached with the demonstration high-resolution product are reduced by up to one third, or up to half in the northeast Atlantic region. The residual noises were optimally filtered from full-rate measurements, taking into consideration the different observing capabilities of the altimeters processed. A specific data recovery strategy was applied, significantly optimizing the data availability, both in the coastal and open ocean areas. This demonstration L3 product is thus better resolved than the conventional 1 Hz product, especially near the coast, where it is defined up to ~5 km against ~10 km for the 1 Hz version. Multi-mission cross-calibration processing was also optimized with an improved long-wavelength error (LWE) correction, leading to a better consistency between tracks, with a 9–15% reduction in SLA variance at cross-overs. The new L3 product improves the overall consistency with tide gauge measurements, with a reduction in SLA differences variance by 5 and 17% compared with the 1 Hz product from the S3A and Jason-3 (J3) measurements, respectively. Primarily intended for regional applications, this product can significantly contribute to improving high-resolution numerical model output via data assimilation. It also opens new perspectives for a better understanding of regional sea-surface dynamics, with an improved representation of the coastal currents and a refined spectral content revealing the unbalanced signal.

Multimodal 4DVarNets for the Reconstruction of Sea Surface Dynamics From SST-SSH Synergies

The space-time reconstruction of sea surface dynamics from satellite observations is a challenging inverse problem due to the associated irregular sampling. Satellite altimetry provides a direct observation of the sea surface height (SSH), which relates to the divergence-free component of sea surface currents. The associated sampling pattern prevents operational schemes from retrieving fine-scale dynamics, typically below 10 days. By contrast, other satellite sensors provide higher-resolution observations of sea surface tracers such as sea surface temperature (SST). Multimodal inversion schemes then arise as appealing approaches. Though theoretical evidence supports the existence of an explicit relationship between sea surface temperature and sea surface dynamics under specific dynamical regimes, the generalization to the variety of upper ocean dynamical regimes is complex. Here, we investigate this issue from a physics-informed learning perspective. We introduce a trainable multimodal inversion scheme for the reconstruction of sea surface dynamics from multi-source satellite-derived observations, namely satellite-derived SSH and SST data. The proposed multimodal 4DVarNet schemes combine a variational formulation involving trainable observation and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a priori</i> terms with a trainable gradient-based solver. An observing system simulation experiment for a Gulf Stream region supports the relevance of our approach compared with state-of-the-art schemes. We report a relative improvement greater than 60% compared with the operational altimetry product in terms of root mean square error and resolved space-time scales. We discuss further the potential and the limitations of the proposed approach for the reconstruction and forecasting of geophysical dynamics from irregularly-sampled satellite observations.

Interannual to decadal sea level variability in the subpolar North Atlantic: the role of propagating signals

Abstract. The gyre-scale, dynamic sea surface height (SSH) variability signifies the spatial redistribution of heat and freshwater in the ocean, influencing the ocean circulation, weather, climate, sea level, and ecosystems. It is known that the first empirical orthogonal function (EOF) mode of the interannual SSH variability in the North Atlantic exhibits a tripole gyre pattern, with the subtropical gyre varying out of phase with both the subpolar gyre and the tropics, influenced by the low-frequency North Atlantic Oscillation. Here, we show that the first EOF mode explains the majority (60 %–90 %) of the interannual SSH variance in the Labrador and Irminger Sea, whereas the second EOF mode is more influential in the northeastern part of the subpolar North Atlantic (SPNA), explaining up to 60 %–80 % of the regional interannual SSH variability. We find that the two leading modes do not represent physically independent phenomena. On the contrary, they evolve as a quadrature pair associated with a propagation of SSH anomalies from the eastern to the western SPNA. This is confirmed by the complex EOF analysis, which can detect propagating (as opposed to stationary) signals. The analysis shows that it takes about 2 years for sea level signals to propagate from the Iceland Basin to the Labrador Sea, and it takes 7–10 years for the entire cycle of the North Atlantic SSH tripole to complete. The observed westward propagation of SSH anomalies is linked to shifting wind forcing patterns and to the cyclonic pattern of the mean ocean circulation in the SPNA. The analysis of regional surface buoyancy fluxes in combination with the upper-ocean temperature and salinity changes suggests a time-dependent dominance of either air–sea heat fluxes or advection in driving the observed SSH tendencies, while the contribution of surface freshwater fluxes (precipitation and evaporation) is negligible. We demonstrate that the most recent cooling and freshening observed in the SPNA since about 2010 were mostly driven by advection associated with the North Atlantic Current. The results of this study indicate that signal propagation is an important component of the North Atlantic SSH tripole, as it applies to the SPNA.

The Dynamic Sea Clutter Simulation of Shore-Based Radar Based on Stokes Waves

The sea clutter model based on the physical sea surface can simulate radar echo at different times and positions and is more suitable for describing dynamic sea clutter than the traditional models based on statistical significance. However, when applying the physical surface model to shore-based radar, the effects of wave nonlinearity, breaking wave, shadow, and radar footprint size must be considered. In this paper, a dynamic sea clutter simulation scheme based on a nonlinear wave is proposed that uses random Stokes waves instead of linear superposition waves to simulate the nonlinear dynamic sea surface and then calculates echo in the form of scattering cells. In this process, the relationship between wind speed and the nonlinear factor of the Stokes wave is derived, a simple model of shadow modulation is provided, and a method for appending the sea clutter spikes formed by breaking waves is developed. The experimental results show that the simulated sea clutter and the real measured clutter have good consistency in intensity, amplitude statistical distribution, Doppler spectrum, and spatiotemporal correlation. The proposed scheme is suitable for the sea clutter simulation of shore-based radar and can also adjust the relevant parameters to extend to other types of sea clutter simulation.

GPU-Accelerated Computation of EM Scattering of a Time-Evolving Oceanic Surface Model II: EM Scattering of Actual Oceanic Surface

Based on marine environmental factors of different sea areas, a high-performance sea clutter time series modeling algorithm for the real sea surface is developed to study the amplitude mean and Doppler spectrum characteristics of sea clutter. The European Centre for Medium-Range Weather Forecasts (ECMWF) data set (ERA-Interim) and ESA’s soil moisture and ocean salinity (SMOS) data set are utilized to establish databases of different marine environmental factors. Combined with the mixed spectrum model, the geometric fine structure of wind-driven sea surface with swell superposition is established by using the double-superposition method (DSM) and comprehensively considering small-scale capillary ripples, large-scale gravity waves and swell. A triangle facet-based sea clutter series modeling algorithm is developed, in which the quasi-specular scattering based on a triangle and the scattering based on gravity wave modulation capillary spectrum are calculated, respectively, and compared with the measured results. For high-resolution radar, dynamic sea surface modeling and sea clutter calculation are very time consuming. In this paper, the Tesla K80 GPU manufactured by NVIDIA in Santa Clara, Computed Unified Device architecture (CUDA) high-performance parallel technology and some optimization strategies are adopted to improve the efficiency of sea clutter modeling. The results can be used to analyze the distribution characteristics of marine factors, the average amplitude and Doppler characteristics of sea clutter in different sea areas.

Контроль течений на поверхности прибрежных морских акваторий дистанционными методами

Object and purpose of research. The compare analysis carried out on the vorticies structure optical satellite pictures observation of the sea surface and the velocities field obtained by the ground HF Doppler radar. The purpose of this research is estimation of the possibility on fast monitoring feasibility assessment for the changes in littoral waters dynamics through joint application of satellite surveillance, radar probing of sea currents, wind data and numerical simulation of water circulation in the area under investigation. Materials and methods. The Sea surface observation data obtained by the satellites Sentinel 1 and 2 and by the coastal Doppler HF radar Sea Sonde in the South-east Black Sea area are analyzing. The additional data on the satellite observation of this area and on the wind condition is used from LANCE processing system [9, 10] and reanalysis NCEP/NCAR [11, 12]. The comparative analysis is carried out on the large vertical structures (LVS) establishing in the research coastal area. The numerical modeling of the water mass circulation in this area is carried out by the software package COHERENS (Belgian Institute of Natural Science) to investigate the role of the wind conditions at LVS appearance in the research area. Main results. The LVS in the vicinity of Sea coast line could be generated, as satellites observations demonstrated, by the vortices arrived along the coast line from the east-south direction in accordance with the Black Sea general circulation flow. Such vortices could be induced by the bottom roughness, rivers discharges and another local sources. Another LVS source could be connected with the wind impact in some affordable direction as demonstrated by the numerical modeling of the coastal water circulation. The continuous currents measurements at the Sea surface by Doppler HF coastal Radar supply the valuable data for further details on the space –time variation of LVS parameters and operational forecast of the hydrology regime in the aquatic areas. The operative numerical modelling of the wind impact to the surface currents structures formation provides the efficient estimation of the local large vorticity structure appearance in the research area. Conclusion. Satellite radar and optical observation provide the large scale control on the Sea surface dynamics conditions, but that is limited by relatively long interval between satellite tracks over the region of interest and do not acquire optical data at the cloud cover. The additional data could be operative obtain from the open internet resource in satellite optical, radar and meteorological data (LANCE, NCEP/NCAR), to get the more details development of the Sea surface dynamics. Sub-satellite Sea currents measurements by HF Doppler radar are useful for the reliable interpretation of satellite pictures and for the proper forecast of the aquatic area dynamics. Operative numerical modelling of the Sea coastal water circulation in accordance with variable meteo data combining with dynamic processes remote measurements could be efficient for the forecast of the environment parameters variation due the water mass transfer. In general the presented results demonstrates the combined application possibilities of the satellite observations, coastal Doppler radar measurements, internet data and operative numerical modelling for operational oceanographic and ecological monitoring of Sea coastal areas with heavy pollution load.

Impacts of the ocean-atmosphere coupling into the very short range prediction system, during the impact of Hurricane Matthew on Cuba

The main goal of this investigation is analyzing the impact of insert the ocean-atmosphere coupling into the very short range prediction system of Cuba. The ocean-atmosphere coupled components of the Coupled Ocean-Atmosphere-Wave-Sediment Transport Modeling System are used for this purpose and the hurricane Matthew is selected as study case. Two experiments are performed: first, using a dynamic sea surface temperature, updated daily in the atmospheric model WRF; and second using a dynamic coupling between the atmospheric and an oceanic models. For the simulated track, the best results are obtained with the coupled system. The impact of coupling on the maximum wind velocities and minimum central pressure is studied. In the coupled system the sea surface temperature has more influence in the surface latent heat fluxes. Also, with this methodology the dry footprint and the behavior of the precipitation field in the presence of a hurricane are studied. This analysis shows that the hurricane acts like an open and self-sustained system in the numerical experiments. The highest differences in the precipitation simulations are in the significant convective area inside the hurricane.