WorldWideScience

Sample records for winds ocean currents

  1. Ocean Current and Wave Effects on Wind Stress Drag Coefficient Over the Global Ocean

    National Research Council Canada - National Science Library

    Kara, A. B; Metzger, E. J; Bourassa, Mark A

    2007-01-01

    ...%), but the notable impact of the latter is only evident in the tropical Pacific Ocean; (2) the presence of waves generally makes winds weaker and C0 lower almost everywhere over the global ocean; (3...

  2. Ka-band Doppler Scatterometer for Measurements of Ocean Vector Winds and Surface Currents

    Data.gov (United States)

    National Aeronautics and Space Administration — Ocean surface currents impact heat transport, surface momentum and gas fluxes, ocean productivity and marine biological communities. Ocean currents also have social...

  3. Investigating the role of wind in generating surface currents over the slope area of the Laptev Sea, Arctic Ocean

    Science.gov (United States)

    Patteson, R. N.

    2017-12-01

    Mixing mechanisms of the Arctic Ocean have profound impacts on sea ice, global ocean dynamics, and arctic communities. This project used a two-year long time series of ocean current velocities collected from eight moorings located on the Eurasian basin, as well as ERA-interim wind data, to compare and assess relationships between current and wind velocities at different depths. Determining the strength of these correlations will further scientific understanding of the degree to which wind influences mixing, with implications for heat flux, diffusion, and sea ice changes. Using statistical analysis, I calculated whether a significant relationship between wind velocity and ocean currents existed beginning at the surface level ( 50m) .The final correlation values, ranging from R = 0.11 to R = 0.28, indicated a weak relationship between wind velocity and ocean currents at the surface for all eight mooring sites. The results for the surface depth imply that correlation likely decreases with increasing depths, and thus further testing of deeper depth levels was unnecessary. This finding suggests that there is another dominant factor at play in the ocean; we postulate that topography exerts a significant influence on subsurface mixing. This study highlights the need for further research of the different mechanisms and their importance in influencing the dynamic structure of the ocean.

  4. Impacts of the Mesoscale Ocean-Atmosphere Coupling on the Peru-Chile Ocean Dynamics: The Current-Induced Wind Stress Modulation

    Science.gov (United States)

    Oerder, V.; Colas, F.; Echevin, V.; Masson, S.; Lemarié, F.

    2018-02-01

    The ocean dynamical responses to the surface current-wind stress interaction at the oceanic mesoscale are investigated in the South-East Pacific using a high-resolution regional ocean-atmosphere coupled model. Two simulations are compared: one includes the surface current in the wind stress computation while the other does not. In the coastal region, absolute wind velocities are different between the two simulations but the wind stress remains very similar. As a consequence, the mean regional oceanic circulation is almost unchanged. On the contrary, the mesoscale activity is strongly reduced when taking into account the effect of the surface current on the wind stress. This is caused by a weakening of the eddy kinetic energy generation near the coast by the wind work and to intensified offshore eddy damping. We show that, above coherent eddies, the current-stress interaction generates eddy damping through Ekman pumping and eddy kinetic energy dissipation through wind work. This alters significantly the coherent eddy vertical structures compared with the control simulation, weakening the temperature and vorticity anomalies and increasing strongly the vertical velocity anomalies associated to eddies.

  5. Wind and temperature data from current meter in the TOGA - Pacific Ocean (30 N to 30 S) as part of the Equatorial Pacific Ocean Climate Studies (EPOCS), 28 May 1994 to 21 March 1995 (NODC Accession 9800041)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Wind and temperature data were collected using current meter in the TOGA Area - Pacific Ocean (30 N to 30 S) from May 28, 1994 to March 21, 1995. Data were submitted...

  6. Small-scale open ocean currents have large effects on wind wave heights

    Science.gov (United States)

    Ardhuin, Fabrice; Gille, Sarah T.; Menemenlis, Dimitris; Rocha, Cesar B.; Rascle, Nicolas; Chapron, Bertrand; Gula, Jonathan; Molemaker, Jeroen

    2017-06-01

    Tidal currents and large-scale oceanic currents are known to modify ocean wave properties, causing extreme sea states that are a hazard to navigation. Recent advances in the understanding and modeling capability of open ocean currents have revealed the ubiquitous presence of eddies, fronts, and filaments at scales 10-100 km. Based on realistic numerical models, we show that these structures can be the main source of variability in significant wave heights at scales less than 200 km, including important variations down to 10 km. Model results are consistent with wave height variations along satellite altimeter tracks, resolved at scales larger than 50 km. The spectrum of significant wave heights is found to be of the order of 70>>2/>(g2>>2>) times the current spectrum, where >> is the spatially averaged significant wave height, >> is the energy-averaged period, and g is the gravity acceleration. This variability induced by currents has been largely overlooked in spite of its relevance for extreme wave heights and remote sensing.Plain Language SummaryWe show that the variations in currents at scales 10 to 100 km are the main source of variations in wave heights at the same scales. Our work uses a combination of realistic numerical models for currents and waves and data from the Jason-3 and SARAL/AltiKa satellites. This finding will be of interest for the investigation of extreme wave heights, remote sensing, and air-sea interactions. As an immediate application, the present results will help constrain the error budget of the up-coming satellite missions, in particular the Surface Water and Ocean Topography (SWOT) mission, and decide how the data will have to be processed to arrive at accurate sea level and wave measurements. It will also help in the analysis of wave measurements by the CFOSAT satellite.

  7. Current direction, wind wave spectra, and CTD data from moored current meter and CTD casts in the North Atlantic Ocean from 1982-09-15 to 1983-09-15 (NODC Accession 8500148)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction, wind wave spectra, and CTD data were collected using moored current meter and CTD casts in the Gulf of Mexico from September 3, 1982 to September...

  8. OW CCMP Ocean Surface Wind

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Cross-Calibrated Multi-Platform (CCMP) Ocean Surface Wind Vector Analyses (Atlas et al., 2011) provide a consistent, gap-free long-term time-series of monthly...

  9. OW ASCAT Ocean Surface Winds

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Advanced Scatterometer (ASCAT) sensor onboard the EUMETSAT MetOp polar-orbiting satellite provides ocean surface wind observations by means of radar...

  10. Current components, physical, ocean circulation, wind circulation, and other data from moored buoys, CTD casts, drifting buoys, and in situ wind recorders from AIRCRAFT and other platforms from the North Atlantic Ocean and other locations as part of the Seasonal Response of the Equatorial Atlantic Experiment/Français Océan et Climat dans l'Atlantique Equatorial (SEQUAL/FOCAL) project from 1980-01-25 to 1985-12-18 (NODC Accession 8700111)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current components, physical, ocean circulation, wind circulation, and other data were collected from moored buoys, CTD casts, drifting buoys, and in situ wind...

  11. Current meter, phytoplankton, and wind data from moored current meter casts and other instruments in the North Pacific Ocean as part of the Deep Ocean Mining and Environmental Study (DOMES) project, 1975-08-29 to 1977-02-24 (NODC Accession 7700458)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter, phytoplankton, and wind data were collected using moored current meter casts and other instruments in the Gulf of Mexico from August 29, 1975 to...

  12. Wind Forcing of the Pacific Ocean Using Scatterometer Wind Data

    Science.gov (United States)

    Kelly, Kathryn A.

    1999-01-01

    The long-term objective of this research was an understanding of the wind-forced ocean circulation, particularly for the Pacific Ocean. To determine the ocean's response to the winds, we first needed to generate accurate maps of wind stress. For the ocean's response to wind stress we examined the sea surface height (SSH) both from altimeters and from numerical models for the Pacific Ocean.

  13. Wind Generated Ocean Waves

    DEFF Research Database (Denmark)

    Frigaard, Peter

    2001-01-01

    Book review: I. R. Young, Elsevier Ocean Engineering Series, Vol 2. Elsevier Science, Oxford, UK, 1999, 306 pages, hardbound, ISBN 0-08-043317-0, Dfl. 275,00 (US$ 139.50)......Book review: I. R. Young, Elsevier Ocean Engineering Series, Vol 2. Elsevier Science, Oxford, UK, 1999, 306 pages, hardbound, ISBN 0-08-043317-0, Dfl. 275,00 (US$ 139.50)...

  14. Ocean Wave Simulation Based on Wind Field.

    Science.gov (United States)

    Li, Zhongyi; Wang, Hao

    2016-01-01

    Ocean wave simulation has a wide range of applications in movies, video games and training systems. Wind force is the main energy resource for generating ocean waves, which are the result of the interaction between wind and the ocean surface. While numerous methods to handle simulating oceans and other fluid phenomena have undergone rapid development during the past years in the field of computer graphic, few of them consider to construct ocean surface height field from the perspective of wind force driving ocean waves. We introduce wind force to the construction of the ocean surface height field through applying wind field data and wind-driven wave particles. Continual and realistic ocean waves result from the overlap of wind-driven wave particles, and a strategy was proposed to control these discrete wave particles and simulate an endless ocean surface. The results showed that the new method is capable of obtaining a realistic ocean scene under the influence of wind fields at real time rates.

  15. Ocean Wave Simulation Based on Wind Field.

    Directory of Open Access Journals (Sweden)

    Zhongyi Li

    Full Text Available Ocean wave simulation has a wide range of applications in movies, video games and training systems. Wind force is the main energy resource for generating ocean waves, which are the result of the interaction between wind and the ocean surface. While numerous methods to handle simulating oceans and other fluid phenomena have undergone rapid development during the past years in the field of computer graphic, few of them consider to construct ocean surface height field from the perspective of wind force driving ocean waves. We introduce wind force to the construction of the ocean surface height field through applying wind field data and wind-driven wave particles. Continual and realistic ocean waves result from the overlap of wind-driven wave particles, and a strategy was proposed to control these discrete wave particles and simulate an endless ocean surface. The results showed that the new method is capable of obtaining a realistic ocean scene under the influence of wind fields at real time rates.

  16. Ocean Wave Simulation Based on Wind Field

    Science.gov (United States)

    2016-01-01

    Ocean wave simulation has a wide range of applications in movies, video games and training systems. Wind force is the main energy resource for generating ocean waves, which are the result of the interaction between wind and the ocean surface. While numerous methods to handle simulating oceans and other fluid phenomena have undergone rapid development during the past years in the field of computer graphic, few of them consider to construct ocean surface height field from the perspective of wind force driving ocean waves. We introduce wind force to the construction of the ocean surface height field through applying wind field data and wind-driven wave particles. Continual and realistic ocean waves result from the overlap of wind-driven wave particles, and a strategy was proposed to control these discrete wave particles and simulate an endless ocean surface. The results showed that the new method is capable of obtaining a realistic ocean scene under the influence of wind fields at real time rates. PMID:26808718

  17. Assessing Global Ocean Wind Energy Resources Using Multiple Satellite Data

    Directory of Open Access Journals (Sweden)

    Qiaoying Guo

    2018-01-01

    Full Text Available Wind energy, as a vital renewable energy source, also plays a significant role in reducing carbon emissions and mitigating climate change. It is therefore of utmost necessity to evaluate ocean wind energy resources for electricity generation and environmental management. Ocean wind distribution around the globe can be obtained from satellite observations to compensate for limited in situ measurements. However, previous studies have largely ignored uncertainties in ocean wind energy resources assessment with multiple satellite data. It is against this background that the current study compares mean wind speeds (MWS and wind power densities (WPD retrieved from scatterometers (QuikSCAT, ASCAT and radiometers (WindSAT and their different combinations with National Data Buoy Center (NDBC buoy measurements at heights of 10 m and 100 m (wind turbine hub height above sea level. Our results show an improvement in the accuracy of wind resources estimation with the use of multiple satellite observations. This has implications for the acquisition of reliable data on ocean wind energy in support of management policies.

  18. The Interaction of Ocean Waves and Wind

    Science.gov (United States)

    Janssen, Peter

    2004-10-01

    Describing in detail the two-way interaction between wind and ocean waves, this book discusses ocean wave evolution in accordance with the energy balance equation. An extensive overview of nonlinear transfer is given, and the role of four-wave interactions in the generation of extreme events as well as the effects on ocean circulation is included. The volume will interest ocean wave modellers, physicists, applied mathematicians, and engineers.

  19. Southern Ocean carbon-wind stress feedback

    Science.gov (United States)

    Bronselaer, Ben; Zanna, Laure; Munday, David R.; Lowe, Jason

    2018-02-01

    The Southern Ocean is the largest sink of anthropogenic carbon in the present-day climate. Here, Southern Ocean pCO2 and its dependence on wind forcing are investigated using an equilibrium mixed layer carbon budget. This budget is used to derive an expression for Southern Ocean pCO2 sensitivity to wind stress. Southern Ocean pCO2 is found to vary as the square root of area-mean wind stress, arising from the dominance of vertical mixing over other processes such as lateral Ekman transport. The expression for pCO2 is validated using idealised coarse-resolution ocean numerical experiments. Additionally, we show that increased (decreased) stratification through surface warming reduces (increases) the sensitivity of the Southern Ocean pCO2 to wind stress. The scaling is then used to estimate the wind-stress induced changes of atmospheric pCO_2 in CMIP5 models using only a handful of parameters. The scaling is further used to model the anthropogenic carbon sink, showing a long-term reversal of the Southern Ocean sink for large wind stress strength.

  20. Hybrid Ocean Wind Sensor (HOWS) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposed Phase I effort will investigate and develop the necessary innovations to realize the Hybrid Ocean Wind Sensor system that will provide critical...

  1. Ocean Current Retrievals and Applications

    Science.gov (United States)

    Johannessen, J. A.; Holt, B.; Collard, F.; Kudryavtsev, V.; Romeiser, R.; Mouche, A.

    2013-03-01

    Since the SEASAT mission in 1978, spaceborne synthetic aperture radar (SAR) images of ocean scenes have been used successfully for a variety of applications including mesoscale current features. However, although the SAR image expressions frequently manifest presence of frontal boundaries and eddies it is not straightforward to retrieve quantitative estimates from these expressions. To compensate for this limitation forward models, in which a prescribed surface current field as well as sea surface temperature and wind field are invoked, have regularly been used to simulate the SAR image expressions (Kudryavtsev et al., 2005). On the other hand, technology progress in this decade has enabled overcoming this shortcoming to some extent. The split-antenna mode of TerraSAR-X permits an acquisition of two SAR images with a short time lag for along-track interferometry (Romeiser and Runge, 2007; Romeiser et al., 2010). Additionally advanced processing of conventional SAR raw data, demonstrated with ENVISAT ASAR data, permits velocity retrievals at a reduced spatial resolution even with a single antenna (Chapron et al., 2005). Moreover, in a recent paper by Kudryavtsev et al., (2012) the use of sensor synergy has shown great potential for mapping of intense cross-frontal dynamics and vertical motions at the mesoscale to sub-mesoscale. Based on such a synergetic approach combining SST, sun-glitter brightness and radar backscatter anomalies, these studies have demonstrated the ability to obtain consistent and quantitative determination of the location and intensity of the surface current convergence/divergence connected with upwelling/downwelling along frontal zones and eddies. These methodologies and their inherent advantages and limitations are further addressed in this paper.

  2. Intraseasonal meridional current variability in the eastern equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Ogata, T.; Sasaki, H.; Murty, V.S.N.; Sarma, M.S.S.; Masumoto, Y.

    values of the Mixed Rossby-gravity wave at 15-d period. This meridional current variability shows large coherence with the local meridional wind stress, suggesting the upper-ocean responses to the local wind-forcing. A part of the energy of the biweekly...

  3. Variability of wind stress and currents at selected locations over the north Indian Ocean during 1977 and 1979 summer monsoon seasons

    Digital Repository Service at National Institute of Oceanography (India)

    Gopalakrishna, V.V.; Sadhuram, Y.; RameshBabu, V.; Rao, M.V.

    -77 and MONEX-79. In general, the surface wind stress and near surface current fields are strong during a good monsoon year (1977) as compared to those in a bad monsoon year (1979) under similar synoptic conditions together with the prevalence of high...

  4. Slow and Steady: Ocean Circulation. The Influence of Sea Surface Height on Ocean Currents

    Science.gov (United States)

    Haekkinen, Sirpa

    2000-01-01

    The study of ocean circulation is vital to understanding how our climate works. The movement of the ocean is closely linked to the progression of atmospheric motion. Winds close to sea level add momentum to ocean surface currents. At the same time, heat that is stored and transported by the ocean warms the atmosphere above and alters air pressure distribution. Therefore, any attempt to model climate variation accurately must include reliable calculations of ocean circulation. Unlike movement of the atmosphere, movement of the ocean's waters takes place mostly near the surface. The major patterns of surface circulation form gigantic circular cells known as gyres. They are categorized according to their general location-equatorial, subtropical, subpolar, and polar-and may run across an entire ocean. The smaller-scale cell of ocean circulation is known' as an eddy. Eddies are much more common than gyres and much more difficult to track in computer simulations of ocean currents.

  5. Impact of Scatterometer Ocean Wind Vector Data on NOAA Operations

    Science.gov (United States)

    Jelenak, Z.; Chang, P.; Brennan, M. J.; Sienkiewicz, J. M.

    2015-12-01

    Near real-time measurements of ocean surface vector winds (OSVW), including both wind speed and direction from non-NOAA satellites, are being widely used in critical operational NOAA forecasting and warning activities. The scatterometer wind data data have had major operational impact in: a) determining wind warning areas for mid-latitude systems (gale, storm,hurricane force); b) determining tropical cyclone 34-knot and 50-knot wind radii. c) tracking the center location of tropical cyclones, including the initial identification of their formation. d) identifying and warning of extreme gap and jet wind events at all latitudes. e) identifying the current location of frontal systems and high and low pressure centers. f) improving coastal surf and swell forecasts Much has been learned about the importance and utility of satellite OSVW data in operational weather forecasting and warning by exploiting OSVW research satellites in near real-time. Since December 1999 when first data from QuikSCAT scatterometer became available in near real time NOAA operations have been benefiting from ASCAT scatterometer observations on MetOp-A and B, Indian OSCAT scatterometer on OceanSat-3 and lately NASA's RapidScat mission on International Space Station. With oceans comprising over 70 percent of the earth's surface, the impacts of these data have been tremendous in serving society's needs for weather and water information and in supporting the nation's commerce with information for safe, efficient, and environmentally sound transportation and coastal preparedness. The satellite OSVW experience that has been gained over the past decade by users in the operational weather community allows for realistic operational OSVW requirements to be properly stated for future missions. Successful model of transitioning research data into operation implemented by Ocean Winds Team in NOAA's NESDIS/STAR office and subsequent data impacts will be presented and discussed.

  6. Aquantis C-Plane Ocean Current Turbine Project

    Energy Technology Data Exchange (ETDEWEB)

    Fleming, Alex [Dehlsen Associates, LLC, Santa Barbara, CA (United States)

    2015-09-16

    The Aquantis 2.5 MW Ocean Current Generation Device technology developed by Dehlsen Associates, LLC (DA) is a derivation of wind power generating technology (a means of harnessing a slow moving fluid) adapted to the ocean environment. The Aquantis Project provides an opportunity for accelerated technological development and early commercialization, since it involves the joining of two mature disciplines: ocean engineering and wind turbine design. The Aquantis Current Plane (C-Plane) technology is an ocean current turbine designed to extract kinetic energy from a current flow. The technology is capable of achieving competitively priced, continuous, base-load, and reliable power generation from a source of renewable energy not before possible in this scale or form.

  7. Computations of wind-driven ocean-induced magnetic fields

    Science.gov (United States)

    Sachl, Libor; Einspigel, David; Martinec, Zdenek

    2016-04-01

    We present the results of computations of the secondary magnetic field induced by ocean motions. Ocean velocities are computed using the baroclinic ocean model LSOMG. The velocities are then used to determine the Lorentz force which is plugged into the magnetic induction code TLAM as a principal forcing. The TLAM is a 2D magnetic induction code based on the thin-shell approximation (Vivier et al., 2004; Tyler et al., 1997). In this approximation, the equation of magnetic induction simplifies significantly, time derivatives of main and induced magnetic fields are neglected as well as the self-induction term. The price for simplification of governing equations is the limited applicability of the resulting system. It is only suitable for slowly evolving processes. In order to meet the condition, we restrict ourselves to the wind (buoyancy) driven ocean circulation, although the LSOMG model is able to model both tidally- and wind-driven circulations. We assess the accuracy of thin-shell approximation in our setup by comparing the results with the Swarm satellite magnetic data. References Tyler, R. H., Mysak, L. A., and Oberhuber, J. M, 1997. Electromagnetic fields generated by a three dimensional global ocean circulation. J. Geophys. Res., 102, 5531-5551. Vivier, F., Meier-Reimer, E., and Tyler, R. H., 2004. Simulations of magnetic fields generated by the Antarctic Circumpolar Current at satellite altitude: Can geomagnetic measurements be used to monitor the flow? Geophys. Res. Lett., 31, L10306, doi:10.1029/2004GL019804.

  8. Ocean Ekman Response to Wind Forcing in Frontal Regions and Implications for Vertical Velocity

    Science.gov (United States)

    Cronin, M. F.; Tozuka, T.

    2016-12-01

    Wind forcing is fundamental to the ocean circulation. According to the classic "Ekman" theory developed in the early twentieth century, wind-induced steady flow spirals to the right of the wind stress in the Northern Hemisphere and to the left in the Southern Hemisphere, resulting in a net wind-forced "Ekman" transport that is 90 degrees to the right of the wind stress in the Northern Hemisphere and to the left in the Southern Hemisphere. This theory, however, assumes that the near-surface ocean is uniform in density (i.e., has no fronts). In frontal regions the surface "geostrophic" currents have a vertical shear aligned with the density front and this oceanic "thermal wind" shear can balance a portion of the surface wind stress. In this study we show that in frontal regions, the classic Ekman response is altered. Surface ocean currents respond to the effective wind stress—the portion of the wind stress that is out of balance with the ocean's surface geostrophic shear. Consequently, the vertical velocity at the base of the mixed layer is better approximated by the curl of the effective wind stress, rather than the full wind stress. Wind blowing along a front can give rise to a local minimum in the effective wind stress and result in a secondary circulation with downwelling on the cold side of the front and upwelling on the warm side. Using data from the high-resolution Japanese Ocean general circulation model For the Earth Simulator (OFES), we show that these frontal effects cannot be ignored in the Tropics or in strong frontal regions in the extratropics, such as found in coastal regions and in western boundary currents of all basins. Furthermore, these frontal effects dominate the classic Ekman response in regions of both hemispheres where trade winds change to westerlies.

  9. The Response of Western Boundary Currents to Intensifying Global Winds

    Science.gov (United States)

    Beal, L. M.; Elipot, S.

    2016-02-01

    Western boundary currents, such as the Agulhas Current, are the most intense meridional flows in the ocean, carrying heat away from the tropics and towards the poles. There is evidence that these current systems are shifting and/or intensifying under anthropogenic climate change, potentially exacerbating warming and extreme weather events in the mid-latitudes. We use new ocean measurements to show that since the early 1990s the Agulhas Current has not strengthened, despite an increase in sea surface temperature indicative of intensification. Rather, the current has been widening, which we attribute to increased eddy activity. Recent analyses of the Kuroshio and East Australia Current hint at similar trends. These results suggest that increased energy input by the winds may be increasing the instability of boundary currents, rather than intensifying their mean flow, with potential impacts on ocean mixing, ventilation, and shelf interactions. Sustained measurements are needed to properly understand the role of these current systems in future climate change.

  10. Simulation of the Impact of New Ocean Surface Wind Measurements on H*Wind Analyses

    Science.gov (United States)

    Miller, Timothy; Atlas, Robert; Black, Peter; Chen, Shuyi; Hood, Robbie; Johnson, James; Jones, Linwood; Ruf, Chris; Uhlhorn, Eric

    2008-01-01

    The H*Wind analysis, a product of the Hurricane Research Division of NOAA's Atlantic Oceanographic and Meteorological Laboratory, brings together wind measurements from a variety of observation platforms into an objective analysis of the distribution of surface wind speeds in a tropical cyclone. This product is designed to improve understanding of the extent and strength of the wind field, and to improve the assessment of hurricane intensity. See http://www.aoml.noaa.gov/hrd/data sub/wind.html. The Hurricane Imaging Radiometer (HIRAD) is a new passive microwave remote sensor for hurricane observations that is currently under development by NASA Marshall Space Flight Center, NOAA Hurricane Research Division, the University of Central Florida and the University of Michigan. HIRAD is being designed to enhance the current real-time airborne ocean surface winds observation capabilities of NOAA and USAF Weather Squadron hurricane hunter aircraft using the operational airbome Stepped Frequency Microwave Radiometer (SFMR). Unlike SFMR, which measures wind speed and rain rate along the ground track directly beneath the aircraft, HIRAD will provide images of the surface wind and rain field over a wide swath (approximately 3 x the aircraft altitude, or approximately 2 km from space). The instrument is described in a separate paper presented at this conference. The present paper describes a set of Observing System Simulation Experiments (OSSEs) in which measurements from the new instrument as well as those from existing instruments (air, surface, and space-based) are simulated from the output of a numerical model from the University of Miami, and those results are used to construct H*Wind analyses. Evaluations will be presented on the relative impact of HIRAD and other instruments on H*Wind analyses, including the use of HIRAD from 2 aircraft altitudes and from a space-based platform.

  11. Indian Ocean surface winds from NCMRWF analysis as compared to ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Indian Ocean surface winds from NCMRWF analysis as compared to QuikSCAT and moored buoy winds. B N Goswami1 and E N Rajagopal2. 1Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore 560 012, India. 2National Centre for Medium Range Weather Forecasting, Department of ...

  12. Auto-correlation analysis of ocean surface wind vectors

    Indian Academy of Sciences (India)

    M. Senthilkumar (Newgen Imaging) 1461 1996 Oct 15 13:05:22

    satellite and in situ measurements. A case study using the TRMM Microwave Imager (TMI) and. Indian Ocean buoy wind speed data resulted in an improvement of about 10%. 1. Introduction. The need for studying temporal variability of oceanic winds has been pointed out by many authors (for example, Ezraty R S 1989).

  13. Wind Diffusivity Current, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality, Modulus

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes science quality Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  14. Wind Diffusivity Current, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality, Meridional

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes science quality Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  15. Wind Diffusivity Current, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality, Zonal

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes science quality Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  16. Aquantis Ocean Current Turbine Development Project Report

    Energy Technology Data Exchange (ETDEWEB)

    Fleming, Alex J.

    2014-08-23

    The Aquantis® Current Plane (“C-Plane”) technology developed by Dehlsen Associates, LLC (DA) and Aquantis, Inc. is an ocean current turbine designed to extract kinetic energy from ocean currents. The technology is capable of achieving competitively priced base-load, continuous, and reliable power generation from a source of renewable energy not before possible in this scale or form.

  17. Auto-correlation analysis of ocean surface wind vectors

    Indian Academy of Sciences (India)

    The nature of the inherent temporal variability of surface winds is analyzed by comparison of winds obtained through different measurement methods. In this work, an auto-correlation analysis of a time series data of surface winds measured in situ by a deep water buoy in the Indian Ocean has been carried out. Hourly time ...

  18. Ocean Surface Wind Speed of Hurricane Helene Observed by SAR

    DEFF Research Database (Denmark)

    Xu, Qing; Cheng, Yongcun; Li, Xiaofeng

    2011-01-01

    The hurricanes can be detected by many remote sensors, but synthetic aperture radar (SAR) can yield high-resolution (sub-kilometer) and low-level wind information that cannot be seen below the cloud by other sensors. In this paper, an assessment of SAR capability of monitoring high......-resolution hurricane was conducted. A case study was carried out to retrieve ocean surface wind field from C-band RADARSAT-1 SAR image which captured the structure of hurricane Helene over the Atlantic Ocean on 20 September, 2006. With wind direction from the outputs of U.S. Navy Operational Global Atmospheric...... CIWRAP models have been tested to extract wind speed from SAR data. The SAR retrieved ocean surface winds were compared to the aircraft wind speed observations from stepped frequency microwave radiometer (SFMR). The results show the capability of hurricane wind monitoring by SAR....

  19. TropFlux wind stresses over the tropical oceans: Evaluation and comparison with other products

    Digital Repository Service at National Institute of Oceanography (India)

    PraveenKumar, B.; Vialard, J.; Lengaigne, M.; Murty, V.S.N.; McPhaden, M.J.; Cronin, M.F.; Pinsard, F.; Reddy, K.G.

    the hourly values. Note that, we neglected surface currents (which are not always available) while computing wind stresses at these moorings. 3. The TropFlux wind stress product In this section, we first present the methodology for computing Trop... onset. Hence, we recommend the use of TropFlux for studies of equatorial ocean dynamics. Key words: TropFlux, tropics, air-sea momentum fluxes, wind stress products validation. 3 1. Introduction The tropics are home to many climatically relevant...

  20. SSMI wind speed measurements over the Southern Hemisphere oceans

    Science.gov (United States)

    Halpern, David

    1993-01-01

    The Special Sensor Microwave Imager (SSMI) carried by the USAF Defense Meteorological Satellite Program spacecraft correlates the intensity of microwave radiation emitted at the ocean surface with the 10-m height wind speed. The 4-year mean global features of the SSMI data were similar to the climatological-mean annual wind speed estimated from ship reports. Time series of area-weighted 60 deg S - zero deg monthly mean wind speeds indicated that the South Indian Ocean had the largest wind speeds throughout the year.

  1. Geoengineering Downwelling Ocean Currents. A Cost Assessment

    International Nuclear Information System (INIS)

    Zhou, S.; Flynn, P.C.

    2005-01-01

    Downwelling ocean currents carry carbon into the deep ocean (the solubility pump), and play a role in controlling the level of atmospheric carbon. The formation of North Atlantic Deep Water (NADW) also releases heat to the atmosphere, which is a contributor to a mild climate in Europe. One possible response to the increase in anthropogenic carbon in the atmosphere and to the possible weakening of the NADW is modification of downwelling ocean currents, by an increase in carbon concentration or volume. This study assesses the costs of seven possible methods of modifying downwelling currents, including using existing industrial techniques for exchange of heat between water and air. Increasing carbon concentration in downwelling currents is not practical due to the high degree of saturation of high latitude surface water. Two of the methods for increasing the volume of downwelling currents were found to be impractical, and four were too expensive to warrant further consideration. Formation of thicker sea ice by pumping ocean water onto the surface of ice sheets is the least expensive of the methods identified for enhancing downwelling ocean currents. Modifying downwelling ocean currents is highly unlikely to ever be a competitive method of sequestering carbon in the deep ocean, but may find future application for climate modification

  2. Ocean Mixed Layer Response to Gap Wind Scenarios

    National Research Council Canada - National Science Library

    Konstantinou, Nikolaos

    2006-01-01

    This study focuses on understanding the oceanic response to gap outflow and the air-sea interaction processes during the gap wind event between 26 and 28 February 2004 over the Gulf of Tehuantepec, Mexico. The U.S...

  3. Early stages of wind wave and drift current generation under non-stationary wind conditions.

    Science.gov (United States)

    Robles-Diaz, Lucia; Ocampo-Torres, Francisco J.; Branger, Hubert

    2016-04-01

    Generation and amplification mechanisms of ocean waves are well understood under constant wind speed or limited fetch conditions. Under these situations, the momentum and energy transfers from air to water are also quite well known. However during the wind field evolution over the ocean, we may observe sometime high wind acceleration/deceleration situations (e.g. Mexican Tehuano or Mediterranean Mistral wind systems). The evolution of wave systems under these conditions is not well understood. The purpose of these laboratory experiments is to better understand the early stages of water-waves and surface-drift currents under non-stationary wind conditions and to determine the balance between transfers creating waves and surface currents during non-equilibrium situations. The experiments were conducted in the Institut Pythéas wind-wave facility in Marseille-France. The wave tank is 40 m long, 2.7 m wide and 1 m deep. The air section is 50 m long, 3 m wide and 1.8 m height. We used 11 different resistive wave-gauges located along the tank. The momentum fluxes in the air column were estimated from single and X hot-film anemometer measurements. The sampling frequency for wind velocity and surface displacement measurements was 256 Hz. Water-current measurements were performed with a profiling velocimeter. This device measures the first 3.5 cm of the water column with a frequency rate of 100Hz. During the experiments, the wind intensity was abruptly modified with a constant acceleration and deceleration over time. We observed that wind drag coefficient values for accelerated wind periods are lower than the ones reported in previous studies for constant wind speed (Large and Pond 1981; Ocampo-Torres et al. 2010; Smith 1980; Yelland and Taylor 1996). This is probably because the turbulent boundary layer is not completely developed during the increasing-wind sequence. As it was reported in some theoretical studies (Miles 1957; Phillips 1957; Kahma and Donelan 1988), we

  4. Indian Ocean surface winds from NCMRWF analysis as compared to ...

    Indian Academy of Sciences (India)

    The quality of the surface wind analysis at the National Centre for Medium Range Weather Forecasts (NCMRWF), New Delhi over the tropical Indian Ocean and its improvement in 2001 are examined by comparing it with in situ buoy measurements and satellite derived surface winds from NASA QuikSCAT satellite (QSCT) ...

  5. Interpretation of nonlinearity in wind generated ocean surface waves

    Digital Repository Service at National Institute of Oceanography (India)

    Varkey, M.J.

    This study attempts to resolve a mix-up between a physical process and its mathematical interpretation in the context of wind waves on ocean surface. Wind generated wave systems, are conventionally interpreted as a result of interaction of a number...

  6. The current wind energy programme in Italy

    International Nuclear Information System (INIS)

    Ambrosini, G.; Foli, U.; Sesto, E.; Vigotti, R.

    1991-01-01

    In Italy, the main activities in the field of wind energy are carried out by two state-owned organizations, ENEA (Italian National Agency for New Technologies, Energy and the Environment) and ENEL (Italian National Electricity Board), and two major wind turbine generator manufacturers, Alenia/WEST and Riva Calzoni, within the framework of a national programme which is supervized by the Ministry of Industry and Commerce. The work currently under way concerns both wind power plant siting and the development and testing of Italian-made wind turbine generators ranging from 5 to 1500 kW in power. In addition, programmes aimed at constructing wind-farms made up of medium-sized machines (200-400 kW) have recently been launched

  7. Wind Diffusivity Current, METOP ASCAT, 0.25 degrees, Global, Near Real Time, Modulus

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  8. Wind Diffusivity Current, METOP ASCAT, 0.25 degrees, Global, Near Real Time, Meridional

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  9. Wind Diffusivity Current, METOP ASCAT, 0.25 degrees, Global, Near Real Time, Zonal

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  10. Modeling Studies of Wind and Thermohaline Forcing on the California Current System

    National Research Council Canada - National Science Library

    Vance, Phillip

    1997-01-01

    A high-resolution, multi-level, primitive equation model is initialized with climatological data to study the combined effects of wind and thermohaline forcing on the ocean circulation of the California Current System (CCS...

  11. Self-Organizing Maps-based ocean currents forecasting system

    Science.gov (United States)

    Vilibić, Ivica; Šepić, Jadranka; Mihanović, Hrvoje; Kalinić, Hrvoje; Cosoli, Simone; Janeković, Ivica; Žagar, Nedjeljka; Jesenko, Blaž; Tudor, Martina; Dadić, Vlado; Ivanković, Damir

    2016-03-01

    An ocean surface currents forecasting system, based on a Self-Organizing Maps (SOM) neural network algorithm, high-frequency (HF) ocean radar measurements and numerical weather prediction (NWP) products, has been developed for a coastal area of the northern Adriatic and compared with operational ROMS-derived surface currents. The two systems differ significantly in architecture and algorithms, being based on either unsupervised learning techniques or ocean physics. To compare performance of the two methods, their forecasting skills were tested on independent datasets. The SOM-based forecasting system has a slightly better forecasting skill, especially during strong wind conditions, with potential for further improvement when data sets of higher quality and longer duration are used for training.

  12. Wind Resource Estimation using QuikSCAT Ocean Surface Winds

    DEFF Research Database (Denmark)

    Xu, Qing; Zhang, Guosheng; Cheng, Yongcun

    2011-01-01

    In this study, the offshore wind resources in the East China Sea and South China Sea were estimated from over ten years of QuikSCAT scatterometer wind products. Since the errors of these products are larger close to the coast due to the land contamination of radar backscatter signal and the compl...

  13. Wind Resource Estimation using QuikSCAT Ocean Surface Winds

    DEFF Research Database (Denmark)

    Xu, Qing; Zhang, Guosheng; Cheng, Yongcun

    2011-01-01

    In this study, the offshore wind resources in the East China Sea and South China Sea were estimated from over ten years of QuikSCAT scatterometer wind products. Since the errors of these products are larger close to the coast due to the land contamination of radar backscatter signal...

  14. Global Ocean Currents Database (GOCD) (NCEI Accession 0093183)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Global Ocean Currents Database (GOCD) is a collection of quality controlled ocean current measurements such as observed current direction and speed obtained from...

  15. Wind changes above warm Agulhas Current eddies

    CSIR Research Space (South Africa)

    Roualt, M

    2016-10-01

    Full Text Available Sea-surface temperature (SST), altimetry derived sea-level anomalies (SLA) and surface current are used south of the Agulhas Current to identify warm core mesoscale ocean eddies presenting a distinct SST perturbation superior to 1(supo...

  16. Application of Satellite-Derived Ocean Surface Winds to the Detection of Weather Systems and the Prediction of Near-Ocean Surface Winds around Hawaii

    Directory of Open Access Journals (Sweden)

    Hsi-Chyi Yeh

    2010-01-01

    Full Text Available The Hawaiian Island chain is surrounded by the open ocean and is an ideal place to conduct the application of QuikSCAT satellite-derived ocean surface winds to the detection of weather systems. With the help of QuikSCAT winds, the associated circulation of the weather systems over the open ocean around Hawaii can be identified. In this study, the obvious cyclonic circulation associated with a Kona storm, the significant wind shift and wind confluence related to the surface cold front, and the anticyclonic circulation related to high-pressure systems for both a strong-wind event and a trade-wind condition are revealed over the open ocean through QuikSCAT winds. The propagation of a cold frontal boundary, defined by the wind shift and wind confluence, also can be clearly detected using the reanalyzed ocean-surface winds.

  17. Evaluating and Extending the Ocean Wind Climate Data Record

    Science.gov (United States)

    Ricciardulli, Lucrezia; Rodriguez, Ernesto; Stiles, Bryan W.; Bourassa, Mark A.; Long, David G.; Hoffman, Ross N.; Stoffelen, Ad; Verhoef, Anton; O'Neill, Larry W.; Farrar, J. Tomas; Vandemark, Douglas; Fore, Alexander G.; Hristova-Veleva, Svetla M.; Turk, F. Joseph; Gaston, Robert; Tyler, Douglas

    2017-01-01

    Satellite microwave sensors, both active scatterometers and passive radiometers, have been systematically measuring near-surface ocean winds for nearly 40 years, establishing an important legacy in studying and monitoring weather and climate variability. As an aid to such activities, the various wind datasets are being intercalibrated and merged into consistent climate data records (CDRs). The ocean wind CDRs (OW-CDRs) are evaluated by comparisons with ocean buoys and intercomparisons among the different satellite sensors and among the different data providers. Extending the OW-CDR into the future requires exploiting all available datasets, such as OSCAT-2 scheduled to launch in July 2016. Three planned methods of calibrating the OSCAT-2 σo measurements include 1) direct Ku-band σo intercalibration to QuikSCAT and RapidScat; 2) multisensor wind speed intercalibration; and 3) calibration to stable rainforest targets. Unfortunately, RapidScat failed in August 2016 and cannot be used to directly calibrate OSCAT-2. A particular future continuity concern is the absence of scheduled new or continuation radiometer missions capable of measuring wind speed. Specialized model assimilations provide 30-year long high temporal/spatial resolution wind vector grids that composite the satellite wind information from OW-CDRs of multiple satellites viewing the Earth at different local times. PMID:28824741

  18. Stability analysis of offshore wind farm and marine current farm

    Science.gov (United States)

    Shawon, Mohammad Hasanuzzaman

    Renewable energy has been playing an important role to meet power demand and 'Green Energy' market is getting bigger platform all over the world in the last few years. Due to massive increase in the prices of fossil fuels along with global warming issues, energy harvesting from renewable energy sources has received considerable interest, nowadays, where extensive researches are going on to ensure optimum use of renewable sources. In order to meet the increasing demand of electricity and power, integration of renewable energy is getting highest priorities around the world. Wind is one of the most top growing renewable energy resources and wind power market penetration is expected to reach 3.35 percent by 2013 from its present market of about 240 GW. A wind energy system is the most environmental friendly, cost effective and safe among all renewable energy resources available. Another promising form of renewable energy is ocean energy which covers 70 % of the earth. Ocean energy can be tapped from waves, tides and thermal elements. Offshore Wind farm (OWF) has already become very popular for large scale wind power integration with the onshore grid. Recently, marine current farm (MCF) is also showing good potential to become mainstream energy sources and already successfully commissioned in United Kingdom. However, squirrel cage induction generator (SCIG) has the stability problem similar to synchronous generator especially during fault location to restore the electromagnetic torque. Series dynamic braking resistor (SDBR) has been known as a useful mean to stabilize fixed speed wind generator system. On the other hand, doubly fed induction generator (DFIG) has the capability of coupling the control of active and reactive power and to provide necessary reactive power demand during grid fault conditions. Series dynamic braking resistor (SDBR) can also be employed with DFIG to limit the rotor over current. An integration of wind and tidal energy represents a new

  19. Ocean Currents: Marine Science Activities for Grades 5-8. Teacher's Guide.

    Science.gov (United States)

    Halversen, Catherine; Beals, Kevin; Strang, Craig

    This teacher's guide attempts to answer questions such as: What causes ocean currents? What impact do they have on Earth's environment? and How have they influenced human history? Seven innovative activities are provided in which students can gain fascinating insights into the earth as the ocean planet. Activities focus on how wind, temperature,…

  20. Ocean Current Power Generator. Final Report

    Energy Technology Data Exchange (ETDEWEB)

    O' Sullivan, G. A.

    2002-07-26

    The Ocean Power Generator is both technically and economically suitable for deployment in the Gulf Stream from the US Navy facility in Dania, Florida. Yet to be completed is the calibration test in the Chesapeake Bay with the prototype dual hydroturbine Underwater Electric Kite. For the production units a revised design includes two ballast tanks mounted as pontoons to provide buoyancy and depth control. The power rating of the Ocean Power Generator has been doubled to 200 kW ready for insertion into the utility grid. The projected cost for a 10 MW installation is $3.38 per watt, a cost that is consistent with wind power pricing when it was in its deployment infancy, and a cost that is far better than photovoltaics after 25 years of research and development. The Gulf Stream flows 24 hours per day, and water flow is both environmentally and ecologically perfect as a renewable energy source. No real estate purchases are necessary, and you cannot see, hear, smell, or touch an Ocean Power Generator.

  1. Simulation of the Impact of New Aircraft and Satellite-Based Ocean Surface Wind Measurements on H*Wind Analyses

    Science.gov (United States)

    Miller, TImothy L.; Atlas, R. M.; Black, P. G.; Case, J. L.; Chen, S. S.; Hood, R. E.; Johnson, J. W.; Jones, L.; Ruf, C. S.; Uhlborn, E. W.

    2008-01-01

    Accurate observations of surface ocean vector winds (OVW) with high spatial and temporal resolution are required for understanding and predicting tropical cyclones. As NASA's QuikSCAT and Navy's WindSat operate beyond their design life, many members of the weather and climate science communities recognize the importance of developing new observational technologies and strategies to meet the essential need for OVW information to improve hurricane intensity and location forecasts. The Hurricane Imaging Radiometer (HIRAD) is an innovative technology development which offers new and unique remotely sensed satellite observations of both extreme oceanic wind events and strong precipitation. It is based on the airborne Stepped Frequency Microwave Radiometer (SFMR), which is the only proven remote sensing technique for observing tropical cyclone (TC) ocean surface wind speeds and rain rates. The proposed HIRAD instrument advances beyond the current nadir viewing SFMR to an equivalent wide-swath SFMR imager using passive microwave synthetic thinned aperture radiometer (STAR) technology. This sensor will operate over 4-7 GHz (C-band frequencies) where the required TC remote sensing physics has been validated by both SFMR and WindSat radiometers. The instrument is described in more detail in a paper by Jones et al. presented to the Tropical Meteorology Special Symposium at this AMS Annual Meeting. Simulated HIRAD passes through a simulation of hurricane Frances are being developed to demonstrate HIRAD estimation of surface wind speed over a wide swath in the presence of heavy rain. These are currently being used in "quick" OSSEs (Observing System Simulation Experiments) with H'Wind analyses as the discriminating tool. The H'Wind analysis, a product of the Hurricane Research Division of NOAA's Atlantic , Oceanographic and Meteorological Laboratory, brings together wind measurements from a variety of observation platforms into an objective analysis of the distribution of wind

  2. Mesoscale atmosphere ocean coupling enhances the transfer of wind energy into the ocean

    Science.gov (United States)

    Byrne, D.; Münnich, M.; Frenger, I.; Gruber, N.

    2016-01-01

    Although it is well established that the large-scale wind drives much of the world's ocean circulation, the contribution of the wind energy input at mesoscales (10–200 km) remains poorly known. Here we use regional simulations with a coupled high-resolution atmosphere–ocean model of the South Atlantic, to show that mesoscale ocean features and, in particular, eddies can be energized by their thermodynamic interactions with the atmosphere. Owing to their sea-surface temperature anomalies affecting the wind field above them, the oceanic eddies in the presence of a large-scale wind gradient provide a mesoscale conduit for the transfer of energy into the ocean. Our simulations show that this pathway is responsible for up to 10% of the kinetic energy of the oceanic mesoscale eddy field in the South Atlantic. The conditions for this pathway to inject energy directly into the mesoscale prevail over much of the Southern Ocean north of the Polar Front. PMID:27292447

  3. Current limiting characteristics of transformer type SFCL with coupled secondary windings according to its winding direction

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Sung Hun [Dept. of Electrical Engineering, Soongsil University, Seoul (Korea, Republic of); Han, Tae Hee [Dept. of Aero Materials Engineering, Jungwon University, Goesan (Korea, Republic of)

    2017-06-15

    In this paper, the current limiting characteristics of the transformer type superconducting fault current limiter (SFCL) with the two coupled secondary windings due to its winding direction were analyzed. To analyze the dependence of transient fault current limiting characteristics on the winding direction of the additional secondary winding, the fault current limiting tests of the SFCL with an additional secondary winding, wound as subtractive polarity winding and additive polarity winding, were carried out. The time interval of quench occurrence between two superconducting elements comprising the transformer type SFCL with the additional secondary winding was confirmed to be affected by the winding direction of the additional secondary winding. In case of the subtractive polarity winding of the additional secondary winding, the time interval of the quench occurrence in two superconducting elements was shorter than the case of the additive polarity winding.

  4. Response of an ocean general circulation model to wind and ...

    Indian Academy of Sciences (India)

    The stretched-coordinate ocean general circulation model has been designed to study the observed variability due to wind and thermodynamic forcings. The model domain extends from 60°N to 60°S and cyclically continuous in the longitudinal direction. The horizontal resolution is 5° × 5° and 9 discrete vertical levels.

  5. Phase spectral composition of wind generated ocean surface waves

    Digital Repository Service at National Institute of Oceanography (India)

    Varkey, M.J.

    A study of the composition of the phase spectra of wind generated ocean surface waves is carried out using wave records collected employing a ship borne wave recorder. It is found that the raw phase spectral estimates could be fitted by the Uniform...

  6. Auto-correlation analysis of ocean surface wind vectors

    Indian Academy of Sciences (India)

    M. Senthilkumar (Newgen Imaging) 1461 1996 Oct 15 13:05:22

    In this work, an auto-correlation analysis of a time series data of surface winds measured in situ by a deep water buoy in the Indian Ocean has been carried out. Hourly time series data available for 240 hours in the month of May, 1999 were subjected to an auto-correlation analysis. The analysis indicates an exponential fall ...

  7. Geophysical potential for wind energy over the open oceans.

    Science.gov (United States)

    Possner, Anna; Caldeira, Ken

    2017-10-24

    Wind turbines continuously remove kinetic energy from the lower troposphere, thereby reducing the wind speed near hub height. The rate of electricity generation in large wind farms containing multiple wind arrays is, therefore, constrained by the rate of kinetic energy replenishment from the atmosphere above. In recent years, a growing body of research argues that the rate of generated power is limited to around 1.5 W m -2 within large wind farms. However, in this study, we show that considerably higher power generation rates may be sustainable over some open ocean areas. In particular, the North Atlantic is identified as a region where the downward transport of kinetic energy may sustain extraction rates of 6 W m -2 and above over large areas in the annual mean. Furthermore, our results indicate that the surface heat flux from the oceans to the atmosphere may play an important role in creating regions where sustained high rates of downward transport of kinetic energy and thus, high rates of kinetic energy extraction may be geophysical possible. While no commercial-scale deep water wind farms yet exist, our results suggest that such technologies, if they became technically and economically feasible, could potentially provide civilization-scale power.

  8. Simulation of the Impact of New Air-Based Ocean Surface Wind Measurements on H*Wind Analyses

    Science.gov (United States)

    Miller, Timothy; Atlas, Robert; Black, Peter; Case, Jonathan; Chen, Shuyi; Hood, Robbie; Jones, Linwood; Ruff, Chris; Uhlhorn, Eric

    2008-01-01

    The H'Wind analysis, a product of the Hurricane Research Division of NOAA's Atlantic Oceanographic and Meteorological Laboratory, brings together wind measurements from a variety of observation platforms into an objective analysis of the distribution of wind speeds in a tropical cyclone. This product is designed to improve understanding of the extent and strength of the wind field, and to improve the assessment of hurricane intensity. See http://www.aoml.noaa.gov/hrd/data sub/wind.html. The Hurricane Imaging Radiometer (HIRad) is a new airborne microwave remote sensor for hurricane observations that is currently under development by NASA Marshall Space Flight Center, NOAA Hurricane Research Division, the University of Central Florida and the University of Michigan. HIRad is being designed to enhance the real-time airborne ocean surface winds observation capabilities of NOAA and USAF Weather Squadron hurricane hunter aircraft using the operational airborne Stepped Frequency Microwave Radiometer (SFMR). Unlike SFMR, which measures wind speed and rain rate along the ground track directly beneath the aircraft, HIRad will provide images of the surface wind and rain field over a wide swath (approx. 3 x the aircraft altitude). The instrument is described in a paper presented to the Hurricanes and Tropical Meteorology Symposium. The present paper describes a set of Observing System Simulation Experiments (OSSEs) in which measurements from the new instrument as well as those from existing instruments (air, surface, and space-based) are simulated from the output of a numerical model from the University of Miami and those results are used to construct H*Wind analyses. Evaluations will be presented on the impact of the HIRad instrument on H'Wind analyses, both in terms of adding it to the full suite of current measurements, as well as using it to replace instrument(s) that may not be functioning at the future tame the HIRad instrument is implemented.

  9. Conflict Resolution for Wind-Optimal Aircraft Trajectories in North Atlantic Oceanic Airspace with Wind Uncertainties

    Science.gov (United States)

    Rodionova, Olga; Sridhar, Banavar; Ng, Hok K.

    2016-01-01

    Air traffic in the North Atlantic oceanic airspace (NAT) experiences very strong winds caused by jet streams. Flying wind-optimal trajectories increases individual flight efficiency, which is advantageous when operating in the NAT. However, as the NAT is highly congested during peak hours, a large number of potential conflicts between flights are detected for the sets of wind-optimal trajectories. Conflict resolution performed at the strategic level of flight planning can significantly reduce the airspace congestion. However, being completed far in advance, strategic planning can only use predicted environmental conditions that may significantly differ from the real conditions experienced further by aircraft. The forecast uncertainties result in uncertainties in conflict prediction, and thus, conflict resolution becomes less efficient. This work considers wind uncertainties in order to improve the robustness of conflict resolution in the NAT. First, the influence of wind uncertainties on conflict prediction is investigated. Then, conflict resolution methods accounting for wind uncertainties are proposed.

  10. On the fast response of the Southern Ocean to changes in the zonal wind

    Directory of Open Access Journals (Sweden)

    D. J. Webb

    2007-09-01

    Full Text Available Model studies of the Southern Ocean, reported here, show that the Antarctic Circumpolar Current responds within two days to changes in the zonal wind stress at the latitudes of Drake Passage. Further investigation shows that the response is primarily barotropic and that, as one might expect, it is controlled by topography. Analysis of the results show that the changes in the barotropic flow are sufficient to transfer the changed surface wind stress to the underlying topography and that during this initial phase baroclinic processes are not involved.

    The model results also show that the Deacon Cell responds to changes in the wind stress on the same rapid time scale. It is shown that the changes in the Deacon Cell can also be explained by the change in the barotropic velocity field, an increase in the zonal wind stress producing an increased northward flow in shallow regions and southward flow where the ocean is deep. This new explanation is unexpected as previously the Deacon Cell has been thought of as a baroclinic feature of the ocean.

    The results imply that where baroclinic processes do appear to be involved in either the zonal momentum balance of the Southern Ocean or the formation of the Deacon Cell, they are part of the long term baroclinic response of the ocean's density field to the changes in the barotropic flow.

  11. Surface wind mixing in the Regional Ocean Modeling System (ROMS)

    Science.gov (United States)

    Robertson, Robin; Hartlipp, Paul

    2017-12-01

    Mixing at the ocean surface is key for atmosphere-ocean interactions and the distribution of heat, energy, and gases in the upper ocean. Winds are the primary force for surface mixing. To properly simulate upper ocean dynamics and the flux of these quantities within the upper ocean, models must reproduce mixing in the upper ocean. To evaluate the performance of the Regional Ocean Modeling System (ROMS) in replicating the surface mixing, the results of four different vertical mixing parameterizations were compared against observations, using the surface mixed layer depth, the temperature fields, and observed diffusivities for comparisons. The vertical mixing parameterizations investigated were Mellor- Yamada 2.5 level turbulent closure (MY), Large- McWilliams- Doney Kpp (LMD), Nakanishi- Niino (NN), and the generic length scale (GLS) schemes. This was done for one temperate site in deep water in the Eastern Pacific and three shallow water sites in the Baltic Sea. The model reproduced the surface mixed layer depth reasonably well for all sites; however, the temperature fields were reproduced well for the deep site, but not for the shallow Baltic Sea sites. In the Baltic Sea, the models overmixed the water column after a few days. Vertical temperature diffusivities were higher than those observed and did not show the temporal fluctuations present in the observations. The best performance was by NN and MY; however, MY became unstable in two of the shallow simulations with high winds. The performance of GLS nearly as good as NN and MY. LMD had the poorest performance as it generated temperature diffusivities that were too high and induced too much mixing. Further observational comparisons are needed to evaluate the effects of different stratification and wind conditions and the limitations on the vertical mixing parameterizations.

  12. Equatorial Indian Ocean subsurface current variability in an Ocean General Circulation Model

    Science.gov (United States)

    Gnanaseelan, C.; Deshpande, Aditi

    2018-03-01

    The variability of subsurface currents in the equatorial Indian Ocean is studied using high resolution Ocean General Circulation Model (OGCM) simulations during 1958-2009. February-March eastward equatorial subsurface current (ESC) shows weak variability whereas strong variability is observed in northern summer and fall ESC. An eastward subsurface current with maximum amplitude in the pycnocline is prominent right from summer to winter during strong Indian Ocean Dipole (IOD) years when air-sea coupling is significant. On the other hand during weak IOD years, both the air-sea coupling and the ESC are weak. This strongly suggests the role of ESC on the strength of IOD. The extension of the ESC to the summer months during the strong IOD years strengthens the oceanic response and supports intensification and maintenance of IODs through modulation of air sea coupling. Although the ESC is triggered by equatorial winds, the coupled air-sea interaction associated with IODs strengthens the ESC to persist for several seasons thereby establishing a positive feedback cycle with the surface. This suggests that the ESC plays a significant role in the coupled processes associated with the evolution and intensification of IOD events by cooling the eastern basin and strengthening thermocline-SST (sea surface temperature) interaction. As the impact of IOD events on Indian summer monsoon is significant only during strong IOD years, understanding and monitoring the evolution of ESC during these years is important for summer monsoon forecasting purposes. There is a westward phase propagation of anomalous subsurface currents which persists for a year during strong IOD years, whereas such persistence or phase propagation is not seen during weak IOD years, supporting the close association between ESC and strength of air sea coupling during strong IOD years. In this study we report the processes which strengthen the IOD events and the air sea coupling associated with IOD. It also unravels

  13. Interaction between surface wind and ocean circulation in the Carolina Capes in a coupled low-order model

    Energy Technology Data Exchange (ETDEWEB)

    Xie, L.; Pietrafesa, L.J.; Raman, S.

    1997-03-18

    Interactions between surface winds and ocean currents over an east-coast continental shelf are studied using a simple mathematical model. The model physics include cross-shelf advection of sea surface temperature (SST) by Ekman drift, upwelling due to Ekman transport divergence, differential heating of the low-level atmosphere by a cross-shelf SST gradient, and the Coriolis effect. Additionally, the effects of diabatic cooling of surface waters due to air-sea heat exchange and of the vertical density stratification on the thickness of the upper ocean Ekman layer are considered. The model results are qualitatively consistent with observed wind-driven coastal ocean circulation and surface wind signatures induced by SST. This simple model also demonstrates that two-way air-sea interaction plays a significant role in the subtidal frequency variability of coastal ocean circulation and mesoscale variability of surface wind fields over coastal waters.

  14. Local inertial oscillations in the surface ocean generated by time-varying winds

    Science.gov (United States)

    Chen, Shengli; Polton, Jeff A.; Hu, Jianyu; Xing, Jiuxing

    2015-12-01

    A new relationship is presented to give a review study on the evolution of inertial oscillations in the surface ocean locally generated by time-varying wind stress. The inertial oscillation is expressed as the superposition of a previous oscillation and a newly generated oscillation, which depends upon the time-varying wind stress. This relationship is employed to investigate some idealized wind change events. For a wind series varying temporally with different rates, the induced inertial oscillation is dominated by the wind with the greatest variation. The resonant wind, which rotates anti-cyclonically at the local inertial frequency with time, produces maximal amplitude of inertial oscillations, which grows monotonically. For the wind rotating at non-inertial frequencies, the responses vary periodically, with wind injecting inertial energy when it is in phase with the currents, but removing inertial energy when it is out of phase. The wind rotating anti-cyclonically with time is much more favorable to generate inertial oscillations than the cyclonic rotating wind. The wind with a frequency closer to the inertial frequency generates stronger inertial oscillations. For a diurnal wind, the induced inertial oscillation is dependent on latitude and is most significant at 30 °. This relationship is also applied to examine idealized moving cyclones. The inertial oscillation is much stronger on the right-hand side of the cyclone path than on the left-hand side (in the northern hemisphere). This is due to the wind being anti-cyclonic with time on the right-hand side, but cyclonic on the other side. The inertial oscillation varies with the cyclone translation speed. The optimal translation speed generating the greatest inertial oscillations is 2 m/s at the latitude of 10 ° and gradually increases to 6 m/s at the latitude of 30 °.

  15. Temperature profile and other data collected using current meter from the CHAIN from the Atlantic Ocean in part of the International Decade of Ocean Exploration / Mid-Ocean Dynamics Experiment from 12 February 1969 to 16 March 1972 (NODC Accession 7601355)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile, current meter, and wind speed/direction data were collected using current meter from the TRIDENT, KNORR, and BILLIE 2 in the Atlantic Ocean from...

  16. Error estimates for CCMP ocean surface wind data sets

    Science.gov (United States)

    Atlas, R. M.; Hoffman, R. N.; Ardizzone, J.; Leidner, S.; Jusem, J.; Smith, D. K.; Gombos, D.

    2011-12-01

    The cross-calibrated, multi-platform (CCMP) ocean surface wind data sets are now available at the Physical Oceanography Distributed Active Archive Center from July 1987 through December 2010. These data support wide-ranging air-sea research and applications. The main Level 3.0 data set has global ocean coverage (within 78S-78N) with 25-kilometer resolution every 6 hours. An enhanced variational analysis method (VAM) quality controls and optimally combines multiple input data sources to create the Level 3.0 data set. Data included are all available RSS DISCOVER wind observations, in situ buoys and ships, and ECMWF analyses. The VAM is set up to use the ECMWF analyses to fill in areas of no data and to provide an initial estimate of wind direction. As described in an article in the Feb. 2011 BAMS, when compared to conventional analyses and reanalyses, the CCMP winds are significantly different in some synoptic cases, result in different storm statistics, and provide enhanced high-spatial resolution time averages of ocean surface wind. We plan enhancements to produce estimated uncertainties for the CCMP data. We will apply the method of Desroziers et al. for the diagnosis of error statistics in observation space to the VAM O-B, O-A, and B-A increments. To isolate particular error statistics we will stratify the results by which individual instruments were used to create the increments. Then we will use cross-validation studies to estimate other error statistics. For example, comparisons in regions of overlap for VAM analyses based on SSMI and QuikSCAT separately and together will enable estimating the VAM directional error when using SSMI alone. Level 3.0 error estimates will enable construction of error estimates for the time averaged data sets.

  17. Seasonal Variability of Wind Sea and Swell Waves Climate along the Canary Current: The Local Wind Effect

    Directory of Open Access Journals (Sweden)

    Alvaro Semedo

    2018-03-01

    Full Text Available A climatology of wind sea and swell waves along the Canary eastern boundary current area, from west Iberia to Mauritania, is presented. The study is based on the European Centre for Medium-Range Weather Forecasts (ECMWF reanalysis ERA-Interim. The wind regime along the Canary Current, along west Iberia and north-west Africa, varies significantly from winter to summer. High summer wind speeds generate high wind sea waves, particularly along the coasts of Morocco and Western Sahara. Lower winter wind speeds, along with stronger extratropical storms crossing the North Atlantic sub-basin up north lead to a predominance of swell waves in the area during from December to February. In summer, the coast parallel wind interacts with the coastal headlands, increasing the wind speed and the locally generated waves. The spatial patterns of the wind sea or swell regional wave fields are shown to be different from the open ocean, due to coastal geometry, fetch dimensions, and island sheltering.

  18. Energy Generation Potential of West African Ocean Current ...

    African Journals Online (AJOL)

    A review of the West African ocean current energy generating potential is carried out. The peculiarity of the West African ocean characteristic is discussed and the challenges noted. Based on this review, it is found that ocean current represents an alternative source of renewable energy in West Africa in a streamed regular ...

  19. Mechanical Extraction of Power From Ocean Currents and Tides

    Science.gov (United States)

    Jones, Jack; Chao, Yi

    2010-01-01

    A proposed scheme for generating electric power from rivers and from ocean currents, tides, and waves is intended to offer economic and environmental advantages over prior such schemes, some of which are at various stages of implementation, others of which have not yet advanced beyond the concept stage. This scheme would be less environmentally objectionable than are prior schemes that involve the use of dams to block rivers and tidal flows. This scheme would also not entail the high maintenance costs of other proposed schemes that call for submerged electric generators and cables, which would be subject to degradation by marine growth and corrosion. A basic power-generation system according to the scheme now proposed would not include any submerged electrical equipment. The submerged portion of the system would include an all-mechanical turbine/pump unit that would superficially resemble a large land-based wind turbine (see figure). The turbine axis would turn slowly as it captured energy from the local river flow, ocean current, tidal flow, or flow from an ocean-wave device. The turbine axis would drive a pump through a gearbox to generate an enclosed flow of water, hydraulic fluid, or other suitable fluid at a relatively high pressure [typically approx.500 psi (approx.3.4 MPa)]. The pressurized fluid could be piped to an onshore or offshore facility, above the ocean surface, where it would be used to drive a turbine that, in turn, would drive an electric generator. The fluid could be recirculated between the submerged unit and the power-generation facility in a closed flow system; alternatively, if the fluid were seawater, it could be taken in from the ocean at the submerged turbine/pump unit and discharged back into the ocean from the power-generation facility. Another alternative would be to use the pressurized flow to charge an elevated reservoir or other pumped-storage facility, from whence fluid could later be released to drive a turbine/generator unit at a

  20. Shearwater foraging in the Southern Ocean: the roles of prey availability and winds.

    Directory of Open Access Journals (Sweden)

    Ben Raymond

    Full Text Available BACKGROUND: Sooty (Puffinus griseus and short-tailed (P. tenuirostris shearwaters are abundant seabirds that range widely across global oceans. Understanding the foraging ecology of these species in the Southern Ocean is important for monitoring and ecosystem conservation and management. METHODOLOGY/PRINCIPAL FINDINGS: Tracking data from sooty and short-tailed shearwaters from three regions of New Zealand and Australia were combined with at-sea observations of shearwaters in the Southern Ocean, physical oceanography, near-surface copepod distributions, pelagic trawl data, and synoptic near-surface winds. Shearwaters from all three regions foraged in the Polar Front zone, and showed particular overlap in the region around 140 degrees E. Short-tailed shearwaters from South Australia also foraged in Antarctic waters south of the Polar Front. The spatial distribution of shearwater foraging effort in the Polar Front zone was matched by patterns in large-scale upwelling, primary production, and abundances of copepods and myctophid fish. Oceanic winds were found to be broad determinants of foraging distribution, and of the flight paths taken by the birds on long foraging trips to Antarctic waters. CONCLUSIONS/SIGNIFICANCE: The shearwaters displayed foraging site fidelity and overlap of foraging habitat between species and populations that may enhance their utility as indicators of Southern Ocean ecosystems. The results highlight the importance of upwellings due to interactions of the Antarctic Circumpolar Current with large-scale bottom topography, and the corresponding localised increases in the productivity of the Polar Front ecosystem.

  1. Evaluation of OSCAR ocean surface current product in the tropical ...

    Indian Academy of Sciences (India)

    (Johnson et al. 2007). The OSCAR product is, however, a global product. Thus there is a pressing need to validate this product in the other basins of the world ocean, e.g., in the Indian Ocean. The present study is motivated by this need. In the present study, monthly climatology of OSCAR ocean surface currents in the TIO ...

  2. The Current Situation of Wind Energy in Turkey

    Directory of Open Access Journals (Sweden)

    Raşit Ata

    2013-01-01

    Full Text Available Wind energy applications and turbine installations at different scales have increased since the beginning of this century. As wind energy is an alternative clean energy source compared to the fossil fuels that pollute the atmosphere, systems that convert wind energy to electricity have developed rapidly. Turkey’s domestic fossil fuel resources are extremely limited. In addition, Turkey’s geographical location has several advantages for extensive use of wind power. In this context, renewable energy resources appear to be one of the most efficient and effective solutions for sustainable energy development and environmental pollution prevention in Turkey. Among the renewable sources, Turkey has very high wind energy potential. According to the Organization for Economic Cooperation and Development (OECD Turkey theoretically has 166 TWh a year of wind potential. However the installed wind power capacity is approximately 14% of total economical wind potential. In this study, Turkey’s installed electric power capacity and electric energy production are investigated and also the current situation of wind energy in Turkey is examined. The wind data used in this study were taken from Turkish Wind Energy Association (TUREB for the year 2012. This paper reviews the assessment of wind energy in Turkey as of the end of July 2012 including wind energy applications.

  3. Turbulent wind waves on a water current

    Directory of Open Access Journals (Sweden)

    M. V. Zavolgensky

    2008-05-01

    Full Text Available An analytical model of water waves generated by the wind over the water surface is presented. A simple modeling method of wind waves is described based on waves lengths diagram, azimuthal hodograph of waves velocities and others. Properties of the generated waves are described. The wave length and wave velocity are obtained as functions on azimuth of wave propagation and growth rate. Motionless waves dynamically trapped into the general picture of three dimensional waves are described. The gravitation force does not enter the three dimensional of turbulent wind waves. That is why these waves have turbulent and not gravitational nature. The Langmuir stripes are naturally modeled and existence of the rogue waves is theoretically proved.

  4. Active current control in wind power plants during grid faults

    DEFF Research Database (Denmark)

    Martinez, Jorge; Kjær, Phillip C.; Rodriguez, Pedro

    2010-01-01

    Modern wind power plants are required and designed to ride through faults in electrical networks, subject to fault clearing. Wind turbine fault current contribution is required from most countries with a high amount of wind power penetration. In order to comply with such grid code requirements......, wind turbines usually have solutions that enable the turbines to control the generation of reactive power during faults. This paper addresses the importance of using an optimal injection of active current during faults in order to fulfil these grid codes. This is of relevant importance for severe...... faults, causing low voltages at the point of common coupling. As a consequence, a new wind turbine current controller for operation during faults is proposed. It is shown that to achieve the maximum transfer of reactive current at the point of common coupling, a strategy for optimal setting of the active...

  5. Wind changes above warm Agulhas Current eddies

    CSIR Research Space (South Africa)

    Rouault, M

    2016-01-01

    Full Text Available speeds above the eddies at the instantaneous scale; 20 % of cases had incomplete data due to partial global coverage by the scatterometer for one path. For cases where the wind is stronger above warm eddies, there is no relationship between the increase...

  6. Mid-latitude wind forced ocean circulation studies

    Science.gov (United States)

    Harrison, D. E.

    1981-01-01

    A simple barotropic vorticity equation model was developed to study some of the various modeling factors that affect the characteristics of strong western boundary currents like the Gulf Stream and Kuroshio. Successful prediction of sea surface temperature, both in the climatological mean and over periods as short as 1 month requires that the heating tendency, due to horizontal advection of heat by these currents, be accurately modeled. Conventional, coarse resolution ocean models do not satisfactorily reproduce the dominant features of these currents. It is concluded that it is important to understand why they do not and what must be done to do so in the future.

  7. Current direction, wind wave spectra, and other data from moored current meter casts and other instruments in the Gulf of Mexico during the Brine Disposal project, 1978-10-11 to 1980-03-19 (NODC Accession 8000368)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction, wind wave spectra, and other data were collected using moored current meter casts and other instruments from the CAPT JACK and EXCELLENCE in the...

  8. Current direction, phytoplankton, zooplankton, wind wave spectra, and other data from moored current meter casts and other instruments in the Gulf of Mexico during the Brine Disposal project, 1981-02-07 to 1982-11-01 (NODC Accession 8300055)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction, phytoplankton, zooplankton, wind wave spectra, and other data were collected using moored current meter casts and other instruments in the Gulf of...

  9. Current direction and wind wave spectra data from moored current meter casts in the Gulf of Mexico during the Brine Disposal project, 01 November 1980 - 01 November 1980 (NODC Accession 8100222)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction and wind wave spectra data were collected using moored current meter casts in the Gulf of Mexico from November 1, 1980 to November 1, 1980. Data...

  10. Current direction, benthic organisms, temperature, and wind direction data from moored current meter casts in the Gulf of Mexico during the Brine Disposal project, 22 September 1977 - 30 November 1978 (NODC Accession 7900110)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction, benthic organisms, temperature, and wind direction data were collected using moored current meter casts in the Gulf of Mexico from September 22,...

  11. Current direction and wind wave spectra data from moored current meter casts in the Gulf of Mexico as part of the Brine Disposal project, 1977-02-02 to 1979-01-31 (NODC Accession 7900144)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction, salinity, and wind wave spectra data were collected using moored current meter casts in the Gulf of Mexico from February 2, 1978 to January 31,...

  12. Current direction, benthic organisms, wind wave spectra data from moored current meter casts and other instruments in the Gulf of Mexico during the Brine Disposal project, 25 March 1977 - 01 February 1980 (NODC Accession 8000320)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction, benthic organisms, wind wave spectra, and other data were collected using moored current meter casts in the Gulf of Mexico from March 25, 1977 to...

  13. Current direction and wind wave spectra data from moored current meter casts in the Gulf of Mexico as part of the Brine Disposal project, 1977-12-22 to 1978-10-31 (NODC Accession 7900023)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction, temperature, and wind wave spectra data were collected using moored current meter casts in the Gulf of Mexico from December 22, 1977 to October...

  14. Current direction and wind wave spectra data from moored current meter casts in the Gulf of Mexico as part of the Brine Disposal project, 1977-12-22 to 1978-07-01 (NODC Accession 7900123)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction, temperature, and wind wave spectra data were collected using moored current meter casts in the Gulf of Mexico from December 22, 1977 to October...

  15. Current direction, zooplankton, wind wave spectra, benthic organisms, and other data from moored current meter casts and other instruments in the Gulf of Mexico during the Brine Disposal project, 18 October 1977 to 01 May 1979 (NODC Accession 7900270)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction, zooplankton, benthic organisms, wind wave spectra, and other data were collected using moored current meter casts and other instruments in the...

  16. Wind direction/velocity and current direction/velocity data from current meter casts in a world wide distribution from 1970-12-06 to 1991-10-01 (NODC Accession 9700218)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Wind direction/velocity and current direction/velocity data were collected using current meter casts in a world wide distribution from December 6, 1970 to October 1,...

  17. Current direction, benthic organisms, wind wave spectra, and other data from moored current meter casts and other instruments in the Gulf of Mexico during the Brine Disposal project, 1978-01-12 to 1980-06-01 (NODC Accession 8000465)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction, benthic organisms, wind wave spectra, and other data were collected using moored current meter casts and other instruments from the CAPT JACK and...

  18. Current direction, wind wave spectra, phytoplankton, zooplankton, and other data from moored current meter casts and other instruments in the Gulf of Mexico during the Brine Disposal project, 1977-09-24 to 1981-08-31 (NODC Accession 8100681)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction, chemical, phytoplankton, zooplankton, wind wave spectra, and other data were collected using moored current meter casts and other instruments in...

  19. Evaluation of satellite and reanalysis wind products with in situ wave glider wind observations in the Southern Ocean

    CSIR Research Space (South Africa)

    Schmidt, KM

    2017-12-01

    Full Text Available Surface ocean wind datasets are required to be of high spatial and temporal resolution and high precision to accurately force or be assimilated into coupled atmosphere–ocean numerical models and to understand ocean–atmospheric processes. In situ...

  20. Intercomparison of the Charnock and COARE bulk wind stress formulations for coastal ocean modelling

    Directory of Open Access Journals (Sweden)

    J. M. Brown

    2013-08-01

    Full Text Available The accurate parameterisation of momentum and heat transfer across the air–sea interface is vital for realistic simulation of the atmosphere–ocean system. In most modelling applications accurate representation of the wind stress is required to numerically reproduce surge, coastal ocean circulation, surface waves, turbulence and mixing. Different formulations can be implemented and impact the accuracy of the instantaneous and long-term residual circulation, the surface mixed layer, and the generation of wave-surge conditions. This, in turn, affects predictions of storm impact, sediment pathways, and coastal resilience to climate change. The specific numerical formulation needs careful selection to ensure the accuracy of the simulation. Two wind stress parameterisations widely used in the ocean circulation and the storm surge communities respectively are studied with focus on an application to the NW region of the UK. Model–observation validation is performed at two nearshore and one estuarine ADCP (acoustic Doppler current profiler stations in Liverpool Bay, a hypertidal region of freshwater influence (ROFI with vast intertidal areas. The period of study covers both calm and extreme conditions to test the robustness of the 10 m wind stress component of the Coupled Ocean–Atmosphere Response Experiment (COARE bulk formulae and the standard Charnock relation. In this coastal application a realistic barotropic–baroclinic simulation of the circulation and surge elevation is set-up, demonstrating greater accuracy occurs when using the Charnock relation, with a constant Charnock coefficient of 0.0185, for surface wind stress during this one month period.

  1. Wind energy - current status in the UK

    International Nuclear Information System (INIS)

    Lindley, D.

    1995-01-01

    Twenty two windfarms are operational or are under construction in the U.K. They have a total installed capacity of approximately 140 MW and will generate about 360 GWh in a full year and provide the electricity needs of about 250 000 individuals and save the emission of about 400 000 tonnes of CO 2 each year. Developments so far have required an investment of about Pound 140 million provided mostly by banks and large corporate investors. Financing these projects has broken new ground for renewable technologies and established a framework for the financing of windfarms built using future NFFO contracts. Obtaining planning consents for these windfarms has involved thirteen public inquiries, eight of which have been successful. Four of these remain unused and the result of another is awaited. Statutory and other bodies have responded to the rapid deployment of windfarms by issuing guidelines and these together with Public Inquiry documentation now provide invaluable guidance for the industry. The U.K. market is arguably the most 'open' in Europe and Danish Wind Turbine manufacturers have gained over 50 per cent of the total market. A Japanese manufacturer has gained 25 per cent whilst the major U.K. turbine supplier has gained 17 per cent market share. There are still over thirty manufacturers worldwide and signs that a combination of innovation and market pressures are continuing to reduce the costs of wind energy. (author)

  2. Evaluation of OSCAR ocean surface current product in the tropical ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 122; Issue 1. Evaluation of OSCAR ocean surface current product in the tropical Indian Ocean using in situ data. Rajesh Sikhakolli Rashmi Sharma Sujit Basu B S Gohil Abhijit Sarkar K V S R Prasad. Volume 122 Issue 1 February 2013 pp 187-199 ...

  3. Measurement of global oceanic winds from Seasat-SMMR and its comparison with Seasat-SASS and ALT derived winds

    Science.gov (United States)

    Pandey, Prem C.

    1987-01-01

    The retrieval of ocean-surface wind speed from different channel combinations of Seasat SMMR measurements is demonstrated. Wind speeds derived using the best two channel subsets (10.6 H and 18.0 V) were compared with in situ data collected during the Joint Air-Sea Interaction (JASIN) experiment and an rms difference of 1.5 m/s was found. Global maps of wind speed generated with the present algorithm show that the averaged winds are arranged in well-ordered belts.

  4. Electrostatic Solitary Waves in the Solar Wind: Evidence for Instability at Solar Wind Current Sheets

    Science.gov (United States)

    Malaspina, David M.; Newman, David L.; Wilson, Lynn Bruce; Goetz, Keith; Kellogg, Paul J.; Kerstin, Kris

    2013-01-01

    A strong spatial association between bipolar electrostatic solitary waves (ESWs) and magnetic current sheets (CSs) in the solar wind is reported here for the first time. This association requires that the plasma instabilities (e.g., Buneman, electron two stream) which generate ESWs are preferentially localized to solar wind CSs. Distributions of CS properties (including shear angle, thickness, solar wind speed, and vector magnetic field change) are examined for differences between CSs associated with ESWs and randomly chosen CSs. Possible mechanisms for producing ESW-generating instabilities at solar wind CSs are considered, including magnetic reconnection.

  5. One- to two-month oscillations in SSMI surface wind speed in western tropical Pacific Ocean

    Science.gov (United States)

    Collins, Michael L.; Stanford, John L.; Halpern, David

    1994-01-01

    The 10-m wind speed over the ocean can be estimated from microwave brightness temperature measurements recorded by the Special Sensor Microwave Imager (SSMI) instrument mounted on a polar-orbiting spacecraft. Four-year (1988-1991) time series of average daily 1 deg x 1 deg SSMI wind speeds were analyzed at selected sites in the western tropical Pacific Ocean. One- to two-month period wind speed oscillations with amplitudes statistically significant at the 95% confidence level were observed near Kanton, Eniwetok, Guam, and Truk. This is the first report of such an oscillation in SSMI wind speeds.

  6. Sea surface temperature (SST) and surface current data collected from the Mar Mostro during the around-the-world Volvo Ocean Race (VOR) from 2011-11-05 to 2012-07-12 (NCEI Accession 0130694)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Navigation, surface current, sea surface temperature, wind, and atmospheric pressure data collected by the Mar Mostro during the around-the-world Volvo Ocean Race...

  7. Simulation of the Impact of New Aircraft- and Satellite-Based Ocean Surface Wind Measurements on H*Wind Analyses and Numerical Forecasts

    Science.gov (United States)

    Miller, Timothy; Atlas, Robert; Black, Peter; Chen, Shuyi; Hood, Robbie; Johnson, James; Jones, Linwood; Ruf, Chris; Uhlhorn, Eric; Krishnamurti, T. N.; hide

    2009-01-01

    The Hurricane Imaging Radiometer (HIRAD) is a new airborne microwave remote sensor for hurricane observations that is currently under development by NASA Marshall Space Flight Center, NOAA Hurricane Research Division, the University of Central Florida and the University of Michigan. HIRAD is being designed to enhance the realtime airborne ocean surface winds observation capabilities of NOAA and USAF Weather Squadron hurricane hunter aircraft using the operational airborne Stepped Frequency Microwave Radiometer (SFMR). Unlike SFMR, which measures wind speed and rain rate along the ground track directly beneath the aircraft, HIRAD will provide images of the surface wind and rain field over a wide swath ( 3 x the aircraft altitude). The present paper describes a set of Observing System Simulation Experiments (OSSEs) in which measurements from the new instrument as well as those from existing instruments (air, surface, and space-based) are simulated from the output of a detailed numerical model, and those results are used to construct H*Wind analyses. The H*Wind analysis, a product of the Hurricane Research Division of NOAA s Atlantic Oceanographic and Meteorological Laboratory, brings together wind measurements from a variety of observation platforms into an objective analysis of the distribution of wind speeds in a tropical cyclone. This product is designed to improve understanding of the extent and strength of the wind field, and to improve the assessment of hurricane intensity. See http://www.aoml.noaa.gov/hrd/data_sub/wind.html. Evaluations will be presented on the impact of the HIRAD instrument on H*Wind analyses, both in terms of adding it to the full suite of current measurements, as well as using it to replace instrument(s) that may not be functioning at the future time the HIRAD instrument is implemented. Also shown will be preliminary results of numerical weather prediction OSSEs in which the impact of the addition of HIRAD observations to the initial state

  8. Northerly surface winds over the eastern North Pacific Ocean in spring and summer

    Science.gov (United States)

    Taylor, S.V.; Cayan, D.R.; Graham, N.E.; Georgakakos, K.P.

    2008-01-01

    Persistent spring and summer northerly surface winds are the defining climatological feature of the western coast of North America, especially south of the Oregon coast. Northerly surface winds are important for upwelling and a vast array of other biological, oceanic, and atmospheric processes. Intermittence in northerly coastal surface wind is characterized and wind events are quantitatively defined using coastal buoy data south of Cape Mendocino on the northern California coast. The defined wind events are then used as a basis for composites in order to explain the spatial evolution of various atmospheric and oceanic processes. Wind events involve large-scale changes in the three-dimensional atmospheric circulation including the eastern North Pacific subtropical anticyclone and southeast trade winds. Composites of QSCAT satellite scatterometer wind estimates from 1999 to 2005 based on a single coastal buoy indicate that wind events typically last 72-96 h and result in anomalies in surface wind and Ekman pumping that extend over 1000 kin from the west coast of North America. It may be useful to consider ocean circulation and dependent ecosystem dynamics and the distribution of temperature, moisture, and aerosols in the atmospheric boundary layer in the context of wind events defined herein. Copyright 2008 by the American Geophysical Union.

  9. Assessment of great ocean currents as a source of renewable energy using recent OGCM simulations of the global ocean

    Science.gov (United States)

    Barnier, Bernard; Domina, Anastasiia; Maitre, Thierry; Molines, Jean-Marc; Penduff, Thierry; Le Sommer, Julien; Brasseur, Pierre; Gulev, Sergey

    2017-04-01

    The great wind-driven ocean currents (e.g. Gulf-Stream or Kuroshio) are relatively constant in strength and direction, and they carry a great deal of energy because of the density of water. Technologies are being developed to extract energy from those currents and convert it into a usable power. The paper presents a methodology used to select regions of the global ocean where the properties of the great ocean currents are favourable to the implementation of Turbine Power Plants (TPP) made of submerged rotors driven by the motion of water. The methodology relies on a state-of-the-art eddy-resolving global ocean general circulation model used for real-time ocean forecasting, in which the implementation of a large TPP is represented by an additional drag force applied locally. This system is able to simulate the flow changes induced by the implementation of a power plant in the current, and consequently provides an assessment of the renewable energy that could be recovered and of the possible environmental impact. Our results demonstrate that the flow changes induced by a large TPP (covering the area of a model grid size, i.e. a few km) are highly dependent on the details of local topography, leading to a reduction of the available power that can vary from 25% to 85% according to location. We shall also show that impact of a TPP on the flow can be felt a few 100 kilometres upstream and may in some cases not only impact the flow speed, but also induce a large shift of the main current path.

  10. Observations of Near-Surface Current Shear Help Describe Oceanic Oil and Plastic Transport

    Science.gov (United States)

    Laxague, Nathan J. M.; Ö-zgökmen, Tamay M.; Haus, Brian K.; Novelli, Guillaume; Shcherbina, Andrey; Sutherland, Peter; Guigand, Cédric M.; Lund, Björn; Mehta, Sanchit; Alday, Matias; Molemaker, Jeroen

    2018-01-01

    Plastics and spilled oil pose a critical threat to marine life and human health. As a result of wind forcing and wave motions, theoretical and laboratory studies predict very strong velocity variation with depth over the upper few centimeters of the water column, an observational blind spot in the real ocean. Here we present the first-ever ocean measurements of the current vector profile defined to within 1 cm of the free surface. In our illustrative example, the current magnitude averaged over the upper 1 cm of the ocean is shown to be nearly four times the average over the upper 10 m, even for mild forcing. Our findings indicate that this shear will rapidly separate pieces of marine debris which vary in size or buoyancy, making consideration of these dynamics essential to an improved understanding of the pathways along which marine plastics and oil are transported.

  11. Current and Future Opportunities for Wind Power in the Southeast

    Energy Technology Data Exchange (ETDEWEB)

    Tinnesand, Heidi; Roberts, Owen; Lantz, Eric

    2016-10-05

    This presentation discusses future wind opportunities in the Southeast including factors such as changes in wind turbine technology, historical innovation trends, and forecast demand growth among regions. The presentation covers the current status of wind in the United States at 80-m hub height and the near-future outlook with a hub height at 110 to 140 meters. Future cost reductions in 2030 and beyond are also explored. Heidi Tinnesand presented this information to a utility advisory group meeting in Charlotte, North Carolina, on October 5, 2016.

  12. Western Gulf of Mexico October 1994 Ocean Currents, Geographic NAD83, MMS (1999)[ocean_currents_wgom_Oct_MMS_1994

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the western...

  13. Eastern Gulf of Mexico April 1997 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_egom_Apr_MMS_1997

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the 'eastern'...

  14. Western Gulf of Mexico May 1994 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_wgom_May_MMS_1994

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the western...

  15. Eastern Gulf of Mexico September 1997 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_egom_Sep_MMS_1997

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the 'eastern'...

  16. Eastern Gulf of Mexico June 1997 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_egom_Jun_MMS_1997

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the 'eastern'...

  17. Eastern Gulf of Mexico February 1997 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_egom_Feb_MMS_1997

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the 'eastern'...

  18. Eastern Gulf of Mexico October 1997 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_egom_Oct_MMS_1997

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the 'eastern'...

  19. Western Gulf of Mexico April 1994 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_wgom_Apr_MMS_1994

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the western...

  20. Eastern Gulf of Mexico January 1997 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_egom_Jan_MMS_1997

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the 'eastern'...

  1. Western Gulf of Mexico November 1994 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_wgom_Nov_MMS_1994

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the western...

  2. Western Gulf of Mexico August 1994 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_wgom_Aug_MMS_1994

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the western...

  3. Western Gulf of Mexico July 1994 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_wgom_Jul_MMS_1994

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the western...

  4. Eastern Gulf of Mexico July 1997 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_egom_Jul_MMS_1997

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the 'eastern'...

  5. Eastern Gulf of Mexico March 1997 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_egom_Mar_MMS_1997

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the 'eastern'...

  6. Eastern Gulf of Mexico December 1997 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_egom_Dec_MMS_1997

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the 'eastern'...

  7. Western Gulf of Mexico June 1994 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_wgom_Jun_MMS_1994

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the western...

  8. Western Gulf of Mexico September 1994 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_wgom_Sep_MMS_1994

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the western...

  9. Eastern Gulf of Mexico August 1997 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_egom_Aug_MMS_1997

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the 'eastern'...

  10. Western Gulf of Mexico January 1994 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_wgom_Jan_MMS_1994

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the western...

  11. Eastern Gulf of Mexico November 1997 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_egom_Nov_MMS_1997

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the 'eastern'...

  12. Western Gulf of Mexico December 1994 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_wgom_Dec_MMS_1994

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the western...

  13. Western Gulf of Mexico February 1994 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_wgom_Feb_MMS_1994

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the western...

  14. Eastern Gulf of Mexico May 1997 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_egom_May_MMS_1997

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the 'eastern'...

  15. Western Gulf of Mexico March 1994 Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_wgom_Mar_MMS_1994

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the western...

  16. Current status of wind energy and wind energy policy in Turkey

    International Nuclear Information System (INIS)

    Yaniktepe, B.; Savrun, M.M.; Koroglu, T.

    2013-01-01

    Highlights: • Present installations of wind power in the world. • Focus on the current state, potential, and development of Turkey’s wind energy. • Explain the institutional framework and support/incentive mechanisms in Turkey. • Investigate and give information about the new Turkish Renewable Energy Law. - Abstract: Over the past decades, the importance of renewable and sustainable energy resources has increased in the world due to both the rapid increase in energy demand and disadvantages of the fossil fuels. Many countries, such as Turkey, aim to increase the use of renewable and sustainable energy sources with different incentive mechanisms. In parallel with these incentive methods being implemented, wind energy capacity in Turkey has a remarkable increase in the growing rates of renewable energy sources according to installed wind power. Up to now, several wind power projects have been developed at different regions of Turkey. This paper aims to analyze the potential and development of wind energy systems in Turkey. Besides, the current usage and development of wind power installations have been explored for the World and Turkey in detail at the end of the 2011. Furthermore, this study also presents tax exemption, support, and incentive mechanisms to develop new wind energy investments in Turkey

  17. Wave measurement in severe ocean currents

    Digital Repository Service at National Institute of Oceanography (India)

    Diwan, S.G.; Suryavanshi, A.K.; Nayak, B.U.

    from 2 to 5 knots are observed. As a consequence of prevailing high currents, significant drag forces have been experiencEd. by the buoys and their mooring system causing occasional submergence. Some of the mooring systems and the components adopted...

  18. Drift current under the action of wind and waves

    International Nuclear Information System (INIS)

    Youssef, M.; Spaulding, M.

    1993-01-01

    Accurate estimates of sea surface drift currents are critical to forecasting oil spill transport and fate. Most existing spill models employ a drift factor and deflection angle, based on local wind speed, to estimate the sea surface drift vector. The effects of wind-induced shear and wave-induced transport are lumped together in this formulation. In the present approach, the conservation of momentum, water mass, and turbulent energy equations are solved using an implicit finite difference method to predict the vertical distribution of current, turbulent energy, and eddy viscosity at one point. The model includes coupling between the wave- and shear-induced currents. Input energy from the atmosphere to the turbulent energy and current fields are represented through free-surface boundary conditions. The numerical model showed excellent agreement compared to an analytic solution of the wind-forced shear flow problem. The model was applied to predict surface drift currents for varying wind speeds and predicted results in general agreement with field observations and other numerical and theoretical studies. The model predicted drift factor F (%) and deflection angle A (degrees) decrease with increasing wind speed W (m/s), and can be approximated by the following curve fits: F=3.91-0.318W, A=23.627-7.97 log W. The model was applied to three intentional oil spills conducted on the Norwegian continental shelf in 1991 and predicted the observed trajectories with reasonable accuracy. 24 refs., 17 figs

  19. Impact of Negative Sequence Current Injection by Wind Power Plants

    DEFF Research Database (Denmark)

    Chaudhary, Sanjay; Göksu, Ömer; Teodorescu, Remus

    2013-01-01

    This paper presents an analysis of the impact from negative sequence current injection by wind power plants in power systems under steady-state and short-term unbalanced conditions, including faults. The separate positive and negative sequence current control capability of the grid-side converters...

  20. Surface Currents and Winds at the Delaware Bay Mouth

    Energy Technology Data Exchange (ETDEWEB)

    Muscarella, P A; Barton, N P; Lipphardt, B L; Veron, D E; Wong, K C; Kirwan, A D

    2011-04-06

    Knowledge of the circulation of estuaries and adjacent shelf waters has relied on hydrographic measurements, moorings, and local wind observations usually removed from the region of interest. Although these observations are certainly sufficient to identify major characteristics, they lack both spatial resolution and temporal coverage. High resolution synoptic observations are required to identify important coastal processes at smaller scales. Long observation periods are needed to properly sample low-frequency processes that may also be important. The introduction of high-frequency (HF) radar measurements and regional wind models for coastal studies is changing this situation. Here we analyze synoptic, high-resolution surface winds and currents in the Delaware Bay mouth over an eight-month period (October 2007 through May 2008). The surface currents were measured by two high-frequency radars while the surface winds were extracted from a data-assimilating regional wind model. To illustrate the utility of these monitoring tools we focus on two 45-day periods which previously were shown to present contrasting pictures of the circulation. One, the low-outflow period is from 1 October through 14 November 2007; the other is the high-outflow period from 3 March through 16 April 2008. The large-scale characteristics noted by previous workers are clearly corroborated. Specifically the M2 tide dominates the surface currents, and the Delaware Bay outflow plume is clearly evident in the low frequency currents. Several new aspects of the surface circulation were also identified. These include a map of the spatial variability of the M2 tide (validating an earlier model study), persistent low-frequency cross-mouth flow, and a rapid response of the surface currents to a changing wind field. However, strong wind episodes did not persist long enough to set up a sustained Ekman response.

  1. Current and turbulence measurements at the FINO1 offshore wind energy site: analysis using 5-beam ADCPs

    Science.gov (United States)

    Bakhoday-Paskyabi, Mostafa; Fer, Ilker; Reuder, Joachim

    2018-01-01

    We report concurrent measurements of ocean currents and turbulence at two sites in the North Sea, one site at upwind of the FINO1 platform and the other 200-m downwind of the Alpha Ventus wind farm. At each site, mean currents, Reynolds stresses, turbulence intensity and production of turbulent kinetic energy are obtained from two bottom-mounted 5-beam Nortek Signature1000s, high-frequency Doppler current profiler, at a water depth of approximately 30 m. Measurements from the two sites are compared to statistically identify the effects of wind farm and waves on ocean current variability and the turbulent structure in the water column. Profiles of Reynolds stresses are found to be sensible to both environmental forcing and the wind farm wake-induced distortions in both boundary layers near the surface and the seabed. Production of turbulent kinetic energy and turbulence intensity exhibit approximately similar, but less pronounced, patterns in the presence of farm wake effects.

  2. Effect of Wind Speed on Aerosol Optical Depth over Remote Oceans, Based on Data from the Maritime Aerosol Network

    Science.gov (United States)

    Smirnov, A.; Sayer, A. M.; Holben, B. N.; Hsu, N. C.; Sakerin, S. M.; Macke, A.; Nelson, N. B.; Courcoux, Y.; Smyth, T. J.; Croot, P.; hide

    2012-01-01

    The Maritime Aerosol Network (MAN) has been collecting data over the oceans since November 2006. The MAN archive provides a valuable resource for aerosol studies in maritime environments. In the current paper we investigate correlations between ship-borne aerosol optical depth (AOD) and near-surface wind speed, either measured (onboard or from satellite) or modeled (NCEP). According to our analysis, wind speed influences columnar aerosol optical depth, although the slope of the linear regression between AOD and wind speed is not steep (approx. 0.004 - 0.005), even for strong winds over 10m/s. The relationships show significant scatter (correlation coefficients typically in the range 0.3 - 0.5); the majority of this scatter can be explained by the uncertainty on the input data. The various wind speed sources considered yield similar patterns. Results are in good agreement with the majority of previously published relationships between surface wind speed and ship-based or satellite-based AOD measurements. The basic relationships are similar for all the wind speed sources considered; however, the gradient of the relationship varies by around a factor of two depending on the wind data used

  3. Effects of Southern Hemisphere Wind Changes on the Meridional Overturning Circulation in Ocean Models.

    Science.gov (United States)

    Gent, Peter R

    2016-01-01

    Observations show that the Southern Hemisphere zonal wind stress maximum has increased significantly over the past 30 years. Eddy-resolving ocean models show that the resulting increase in the Southern Ocean mean flow meridional overturning circulation (MOC) is partially compensated by an increase in the eddy MOC. This effect can be reproduced in the non-eddy-resolving ocean component of a climate model, providing the eddy parameterization coefficient is variable and not a constant. If the coefficient is a constant, then the Southern Ocean mean MOC change is balanced by an unrealistically large change in the Atlantic Ocean MOC. Southern Ocean eddy compensation means that Southern Hemisphere winds cannot be the dominant mechanism driving midlatitude North Atlantic MOC variability.

  4. Potential scour for marine current turbines based on experience of offshore wind turbine

    Science.gov (United States)

    Chen, L.; Lam, W. H.; Shamsuddin, A. H.

    2013-06-01

    The oceans have tremendous untapped natural resources. These sources are capable to make significant contribution to our future energy demands. Marine current energy offers sustainable and renewable alternative to conventional sources. Survival problems of Marine Current Turbines (MCTs) need to be addressed due to the harsh marine environment. The analogous researches in wind turbine have been conducted. Some of the results and knowledge are transferable to marine current energy industry. There still exist some gaps in the state of knowledge. Scour around marine structures have been well recognised as an engineering issue as scour is likely to cause structural instability. This paper aims to review different types of foundation of MCTs and potential scour and scour protection around these foundations based on the experience of offshore wind turbine farm.

  5. Ocean's response to Hurricane Frances and its implications for drag coefficient parameterization at high wind speeds

    KAUST Repository

    Zedler, S. E.

    2009-04-25

    The drag coefficient parameterization of wind stress is investigated for tropical storm conditions using model sensitivity studies. The Massachusetts Institute of Technology (MIT) Ocean General Circulation Model was run in a regional setting with realistic stratification and forcing fields representing Hurricane Frances, which in early September 2004 passed east of the Caribbean Leeward Island chain. The model was forced with a NOAA-HWIND wind speed product after converting it to wind stress using four different drag coefficient parameterizations. Respective model results were tested against in situ measurements of temperature profiles and velocity, available from an array of 22 surface drifters and 12 subsurface floats. Changing the drag coefficient parameterization from one that saturated at a value of 2.3 × 10 -3 to a constant drag coefficient of 1.2 × 10-3 reduced the standard deviation difference between the simulated minus the measured sea surface temperature change from 0.8°C to 0.3°C. Additionally, the standard deviation in the difference between simulated minus measured high pass filtered 15-m current speed reduced from 15 cm/s to 5 cm/s. The maximum difference in sea surface temperature response when two different turbulent mixing parameterizations were implemented was 0.3°C, i.e., only 11% of the maximum change of sea surface temperature caused by the storm. Copyright 2009 by the American Geophysical Union.

  6. Ocean's response to Hurricane Frances and its implications for drag coefficient parameterization at high wind speeds

    Science.gov (United States)

    Zedler, S. E.; Niiler, P. P.; Stammer, D.; Terrill, E.; Morzel, J.

    2009-04-01

    The drag coefficient parameterization of wind stress is investigated for tropical storm conditions using model sensitivity studies. The Massachusetts Institute of Technology (MIT) Ocean General Circulation Model was run in a regional setting with realistic stratification and forcing fields representing Hurricane Frances, which in early September 2004 passed east of the Caribbean Leeward Island chain. The model was forced with a NOAA-HWIND wind speed product after converting it to wind stress using four different drag coefficient parameterizations. Respective model results were tested against in situ measurements of temperature profiles and velocity, available from an array of 22 surface drifters and 12 subsurface floats. Changing the drag coefficient parameterization from one that saturated at a value of 2.3 × 10-3 to a constant drag coefficient of 1.2 × 10-3 reduced the standard deviation difference between the simulated minus the measured sea surface temperature change from 0.8°C to 0.3°C. Additionally, the standard deviation in the difference between simulated minus measured high pass filtered 15-m current speed reduced from 15 cm/s to 5 cm/s. The maximum difference in sea surface temperature response when two different turbulent mixing parameterizations were implemented was 0.3°C, i.e., only 11% of the maximum change of sea surface temperature caused by the storm.

  7. NASA CYGNSS Ocean Wind Observations in the 2017 Atlantic Hurricane Season

    Science.gov (United States)

    Ruf, C. S.; Balasubramaniam, R.; Mayers, D.; McKague, D. S.

    2017-12-01

    The CYGNSS constellation of eight satellites was successfully launched on 15 December 2016 into a low inclination (tropical) Earth orbit to measure ocean surface wind speed in the inner core of tropical cyclones with better than 12 hour refresh rates. Each satellite carries a four-channel bi-static radar receiver that measures GPS signals scattered by the ocean, from which ocean surface roughness, near surface wind speed, and air-sea latent heat flux are estimated. The measurements are unique in several respects, most notably in their ability to penetrate through all levels of precipitation, made possible by the low frequency at which GPS operates, and in the frequent sampling of tropical cyclone intensification, made possible by the large number of satellites. Level 2 science data products have been developed for near surface (10 m referenced) ocean wind speed, ocean surface roughness (mean square slope) and latent heat flux. Level 3 gridded versions of the L2 products have also been developed. A set of Level 4 products have also been developed specifically for direct tropical cyclone overpasses. These include the storm intensity (peak sustained winds) and size (radius of maximum winds), its extent (34, 50 and 64 knot wind radii), and its integrated kinetic energy. Results of measurements made during the 2017 Atlantic hurricane season, including frequent overpasses of Hurricanes Harvey, Irma and Maria, will be presented.

  8. Biogeochemical and ecological impacts of boundary currents in the Indian Ocean

    Science.gov (United States)

    Hood, Raleigh R.; Beckley, Lynnath E.; Wiggert, Jerry D.

    2017-08-01

    Monsoon forcing and the unique geomorphology of the Indian Ocean basin result in complex boundary currents, which are unique in many respects. In the northern Indian Ocean, several boundary current systems reverse seasonally. For example, upwelling coincident with northward-flowing currents along the coast of Oman during the Southwest Monsoon gives rise to high productivity which also alters nutrient stoichiometry and therefore, the species composition of the resulting phytoplankton blooms. During the Northeast Monsoon most of the northern Indian Ocean boundary currents reverse and favor downwelling. Higher trophic level species have evolved behavioral responses to these seasonally changing conditions. Examples from the western Arabian Sea include vertical feeding migrations of a copepod (Calanoides carinatus) and the reproductive cycle of a large pelagic fish (Scomberomorus commerson). The impacts of these seasonal current reversals and changes in upwelling and downwelling circulations are also manifested in West Indian coastal waters, where they influence dissolved oxygen concentrations and have been implicated in massive fish kills. The winds and boundary currents reverse seasonally in the Bay of Bengal, though the associated changes in upwelling and productivity are less pronounced. Nonetheless, their effects are observed on the East Indian shelf as, for example, seasonal changes in copepod abundance and zooplankton community structure. In contrast, south of Sri Lanka seasonal reversals in the boundary currents are associated with dramatic changes in the intensity of coastal upwelling, chlorophyll concentration, and catch per unit effort of fishes. Off the coast of Java, monsoon-driven changes in the currents and upwelling strongly impact chlorophyll concentrations, seasonal vertical migrations of zooplankton, and sardine catch in Bali Strait. In the southern hemisphere the Leeuwin is a downwelling-favorable current that flows southward along western Australia

  9. Retrieving current and wind vectors from ATI SAR data: airborne evidence and inversion strategy

    Science.gov (United States)

    Martin, Adrien; Gommenginger, Christine; Chapron, Bertrand; Marquez, José; Doody, Sam

    2017-04-01

    Conventional and along-track interferometric (ATI) Synthetic Aperture Radar (SAR) sense the motion of the ocean surface by measuring the Doppler shift of reflected signals. Together with the water displacement associated with ocean currents, the SAR measurements are also affected by a Wind-wave induced Artefact Surface Velocity (WASV) caused by the velocity of Bragg scatterers and the orbital velocity of ocean surface gravity waves. The WASV has been modelled theoretically in past studies but has been estimated empirically only once using Envisat ASAR. Here we propose, firstly, to evaluate this WASV from airborne ATI SAR data, secondly, to validate the airborne retrieved surface current after correction of the WASV against HF radar measurements and thirdly to examine the best inversion strategy for a an Ocean Surface Current (OSC) satellite mission to retrieve accurately both the ocean surface current vector (OSCV) and the wind vector in the frame of an OSC satellite mission. The airborne ATI SAR data were acquired in the tidally dominated Irish Sea using a Wavemill-type dual-beam SAR interferometer. A comprehensive collection of airborne Wavemill data acquired in a star pattern over a well-instrumented site made it possible to estimate the magnitude and dependence on azimuth and incidence angle of the WASV. The airborne results compare favourably with those reported for Envisat ASAR, empirical model, which has been used to correct for it. Validation of the current retrieval capabilities of the proof-of-concept has been conducted against HF radar giving a precisions typically better than 0.1 m/s for surface current speed and 7° for direction. Comparisons with POLCOMS (1.8 km) indicate that the model reproduces well the overall temporal evolution but does not capture the high spatial variability of ocean surface currents at the maximum ebb flow. Airborne retrieved currents highlight a short-scale spatial variability up to 100m related to bathymetry channels, which

  10. Mitigation of Wind Power Fluctuation by Active Current Control of Variable Speed Wind Turbines

    DEFF Research Database (Denmark)

    Zhang, Yunqian; Chen, Zhe; Hu, Weihao

    2013-01-01

    converter in Simulink. A simple and effective method of wind power fluctuations mitigation by active current control of DFIG is proposed. It smoothes the generator output active power oscillations by adjusting the active current of the DFIG, such that the power oscillation is stored as the kinetic energy...

  11. QuikSCAT and SSM/I ocean surface winds for wind energy

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay; Astrup, Poul; Nielsen, Per

    2007-01-01

    -indexing is based on long-term trends observed in wind climate statistics. It is customary to observe winds and produced power in parallel in order to keep track of performance. Wind-indexing is based on long-term wind observations and the present study investigate variation in offshore and land-based variations...

  12. About New Maps of Surface Currents of the World Ocean

    Science.gov (United States)

    Nikitin, O. P.; Kasyanov, S. Yu.

    2018-01-01

    Using the example of the surface currents map constructed for the Northern Atlantic on the basis of data of modern observations by means of drifting buoys, it is shown that the previously published maps of ocean surface currents, based on ship drift data, have become outdated and require an update. The influence of the bottom relief on the directions of surface layer currents is shown.

  13. On the Decrease of the Oceanic Drag Coefficient in High Winds

    Science.gov (United States)

    Donelan, Mark A.

    2018-02-01

    The sheltering coefficient - prefixing Jeffreys' concept of the exponential wave growth rate at a gas-liquid interface - is shown to be Reynolds number dependent from laboratory measurements of waves and Reynolds stresses. There are two turbulent flow regimes: wind speed range of 2.5 to 30 m/s where the drag coefficients increase with wind speed, and wind speed range of 30 to 50 m/s where sheltering/drag coefficients decrease/saturate with wind speed. By comparing model calculations of drag coefficients - using a fixed sheltering coefficient - with ocean observations over a wind speed range of 1 to 50 m/s a similar Reynolds number dependence of the oceanic sheltering coefficient is revealed. In consequence the drag coefficient is a function of Reynolds number and wave age, and not just wind speed as frequently assumed. The resulting decreasing drag coefficient above 30 m/s is shown to be critical in explaining the rapid intensification so prominent in the climatology of Atlantic hurricanes. The Reynolds number dependence of the sheltering coefficient, when employed in coupled models, should lead to significant improvements in the prediction of intensification and decay of tropical cyclones. A calculation of curvature at the wave crest suggests that at wind speeds above 56.15 m/s all waves-breaking or not-induce steady flow separation leading to a minimum in the drag coefficient. This is further evidence of the veracity of the observations of the oceanic drag coefficient at high winds.

  14. Simulation of the Impact of New Aircraft- and Satellite-based Ocean Surface Wind Measurements on Estimates of Hurricane Intensity

    Science.gov (United States)

    Uhlhorn, Eric; Atlas, Robert; Black, Peter; Buckley, Courtney; Chen, Shuyi; El-Nimri, Salem; Hood, Robbie; Johnson, James; Jones, Linwood; Miller, Timothy; hide

    2009-01-01

    The Hurricane Imaging Radiometer (HIRAD) is a new airborne microwave remote sensor currently under development to enhance real-time hurricane ocean surface wind observations. HIRAD builds on the capabilities of the Stepped Frequency Microwave Radiometer (SFMR), which now operates on NOAA P-3, G-4, and AFRC C-130 aircraft. Unlike the SFMR, which measures wind speed and rain rate along the ground track directly beneath the aircraft, HIRAD will provide images of the surface wind and rain field over a wide swath (approximately 3 times the aircraft altitude). To demonstrate potential improvement in the measurement of peak hurricane winds, we present a set of Observing System Simulation Experiments (OSSEs) in which measurements from the new instrument as well as those from existing platforms (air, surface, and space-based) are simulated from the output of a high-resolution (approximately 1.7 km) numerical model. Simulated retrieval errors due to both instrument noise as well as model function accuracy are considered over the expected range of incidence angles, wind speeds and rain rates. Based on numerous simulated flight patterns and data source combinations, statistics are developed to describe relationships between the observed and true (from the model s perspective) peak wind speed. These results have implications for improving the estimation of hurricane intensity (as defined by the peak sustained wind anywhere in the storm), which may often go un-observed due to sampling limitations.

  15. Annual and interannual variability of scatterometer ocean surface wind over the South China Sea

    DEFF Research Database (Denmark)

    Zhang, GS; Xu, Q.; Gong, Z.

    2014-01-01

    To investigate the annual and interannual variability of ocean surface wind over the South China Sea (SCS), the vector empirical orthogonal function (VEOF) method and the Hilbert-Huang transform (HHT) method were employed to analyze a set of combined satellite scatterometer wind data during...... the period from December 1992 to October 2009. The merged wind data were generated from European Remote Sensing Satellite (ERS)-1/2 Scatterometer, NASA Scatterometer (NSCAT) and NASA's Quick Scatterometer (QuikSCAT) wind products. The first VEOF mode corresponds to a winter-summer mode which accounts for 87...

  16. Resuspension and Shelf-Deep Ocean Exchange in the Northern California Current: New Insights From Underwater Gliders

    Science.gov (United States)

    Erofeev, A.; Barth, J. A.; Shearman, R. K.; Pierce, S. D.

    2016-02-01

    Shelf-deep ocean exchange is dominated by wind-driven upwelling and downwelling in the northern California Current. The interaction of strong, along-shelf jets with coastline and bottom topographic features can also create significant cross-margin exchange. We are using data from over 60,000 kilometers of autonomous underwater glider tracks to understand the temporal and spatial distribution of shelf-deep ocean exchange off central Oregon. Year-round glider observations of temperature, salinity, depth-averaged currents, chlorophyll fluorescence, light backscatter, and colored dissolved organic matter fluorescence from a single cross-margin transect are used to examine shelf-deep ocean exchange mechanisms. During summer, cross-margin exchange is dominated by wind-driven upwelling and the relaxation or reversal of the dominant southward winds. This process has been fairly well observed and studied due to the relatively low sea states and winds during summer. There is far less data from fall and winter off Oregon, a time of strong winds and large waves. We use autonomous underwater gliders to sample during the winter, including through the fall and spring transitions. Glider observations of suspended material detected via light backscatter, show time-space variations in resuspension in the bottom boundary layer due to winds, waves and currents. Examples of shelf-deep ocean exchange are shown by layers with high light backscatter separating from the bottom near the shelf break and extending into the interior along isopycnals. We describe these features and events in relationship to wind-forcing, along-shelf flows, and other forcing mechanisms.

  17. Observation and modeling of tide- and wind-induced surface currents in Galway Bay

    Directory of Open Access Journals (Sweden)

    Lei Ren

    2015-10-01

    Full Text Available A high-frequency radar system has been deployed in Galway Bay, a semi-enclosed bay on the west coast of Ireland. The system provides surface currents with fine spatial resolution every hour. Prior to its use for model validation, the accuracy of the radar data was verified through comparison with measurements from acoustic Doppler current profilers (ADCPs and a good correlation between time series of surface current speeds and directions obtained from radar data and ADCP data. Since Galway Bay is located on the coast of the Atlantic Ocean, it is subject to relatively windy conditions, and surface currents are therefore strongly wind-driven. With a view to assimilating the radar data for forecasting purposes, a three-dimensional numerical model of Galway Bay, the Environmental Fluid Dynamics Code (EFDC, was developed based on a terrain-following vertical (sigma coordinate system. This study shows that the performance and accuracy of the numerical model, particularly with regard to tide- and wind-induced surface currents, are sensitive to the vertical layer structure. Results of five models with different layer structures are presented and compared with radar measurements. A variable vertical structure with thin layers at the bottom and the surface and thicker layers in the middle of the water column was found to be the optimal layer structure for reproduction of tide- and wind-induced surface currents. This structure ensures that wind shear can properly propagate from the surface layer to the sub-surface layers, thereby ensuring that wind forcing is not overdamped by tidal forcing. The vertical layer structure affects not only the velocities at the surface layer but also the velocities further down in the water column.

  18. Observation and modeling of tide- and wind-induced surface currents in Galway Bay

    Directory of Open Access Journals (Sweden)

    Lei REN

    2015-10-01

    Full Text Available A high-frequency radar system has been deployed in Galway Bay, a semi-enclosed bay on the west coast of Ireland. The system provides surface currents with fine spatial resolution every hour. Prior to its use for model validation, the accuracy of the radar data was verified through comparison with measurements from acoustic Doppler current profilers (ADCPs and a good correlation between time series of surface current speeds and directions obtained from radar data and ADCP data. Since Galway Bay is located on the coast of the Atlantic Ocean, it is subject to relatively windy conditions, and surface currents are therefore strongly wind-driven. With a view to assimilating the radar data for forecasting purposes, a three-dimensional numerical model of Galway Bay, the Environmental Fluid Dynamics Code (EFDC, was developed based on a terrain-following vertical (sigma coordinate system. This study shows that the performance and accuracy of the numerical model, particularly with regard to tide- and wind-induced surface currents, are sensitive to the vertical layer structure. Results of five models using different layer structures are presented and compared with radar measurements. A variable vertical structure with thin layers at the bottom and the surface and thicker layers in the middle of the water column was found to be the optimal layer structure for reproduction of tide- and wind-induced surface currents. This structure ensures that wind shear can properly propagate from the surface layer to the sub-surface layers, thereby ensuring that wind forcing is not overdamped by tidal forcing. The vertical layer structure affects not only the velocities at the surface layer but also the velocities further down in the water column.

  19. Wind Forced Variability in Eddy Formation, Eddy Shedding, and the Separation of the East Australian Current

    Science.gov (United States)

    Bull, Christopher Y. S.; Kiss, Andrew E.; Jourdain, Nicolas C.; England, Matthew H.; van Sebille, Erik

    2017-12-01

    The East Australian Current (EAC), like many other subtropical western boundary currents, is believed to be penetrating further poleward in recent decades. Previous observational and model studies have used steady state dynamics to relate changes in the westerly winds to changes in the separation behavior of the EAC. As yet, little work has been undertaken on the impact of forcing variability on the EAC and Tasman Sea circulation. Here using an eddy-permitting regional ocean model, we present a suite of simulations forced by the same time-mean fields, but with different atmospheric and remote ocean variability. These eddy-permitting results demonstrate the nonlinear response of the EAC to variable, nonstationary inhomogeneous forcing. These simulations show an EAC with high intrinsic variability and stochastic eddy shedding. We show that wind stress variability on time scales shorter than 56 days leads to increases in eddy shedding rates and southward eddy propagation, producing an increased transport and southward reach of the mean EAC extension. We adopt an energetics framework that shows the EAC extension changes to be coincident with an increase in offshore, upstream eddy variance (via increased barotropic instability) and increase in subsurface mean kinetic energy along the length of the EAC. The response of EAC separation to regional variable wind stress has important implications for both past and future climate change studies.

  20. Internal variability of the wind-driven ocean circulation

    NARCIS (Netherlands)

    Katsman, C.A.

    2001-01-01

    The ocean circulation is known to vary on a multitude of time and spatial scales. Due to the large heat capacity of the oceans, variations in its circulation have a profound impact on climate. Therefore, understanding the origin of this variability and its sensitivity to physical parameters is an

  1. Evaluation of OSCAR ocean surface current product in the tropical ...

    Indian Academy of Sciences (India)

    combined fashion, have contributed to the superior performance of the present algorithm for generat- ing ocean surface current. Validation and error analysis of the OSCAR pro- ..... EC (figure 4) through the appearance of strong semiannual periodicity. The SEC peaks in July, the peak being smoother in OSCAR climatology.

  2. Assessment of Energy Production Potential from Ocean Currents along the United States Coastline

    Energy Technology Data Exchange (ETDEWEB)

    Haas, Kevin

    2013-09-15

    Increasing energy consumption and depleting reserves of fossil fuels have resulted in growing interest in alternative renewable energy from the ocean. Ocean currents are an alternative source of clean energy due to their inherent reliability, persistence and sustainability. General ocean circulations exist in the form of large rotating ocean gyres, and feature extremely rapid current flow in the western boundaries due to the Coriolis Effect. The Gulf Stream system is formed by the western boundary current of the North Atlantic Ocean that flows along the east coastline of the United States, and therefore is of particular interest as a potential energy resource for the United States. This project created a national database of ocean current energy resources to help advance awareness and market penetration in ocean current energy resource assessment. The database, consisting of joint velocity magnitude and direction probability histograms, was created from data created by seven years of numerical model simulations. The accuracy of the database was evaluated by ORNL?s independent validation effort documented in a separate report. Estimates of the total theoretical power resource contained in the ocean currents were calculated utilizing two separate approaches. Firstly, the theoretical energy balance in the Gulf Stream system was examined using the two-dimensional ocean circulation equations based on the assumptions of the Stommel model for subtropical gyres with the quasi-geostrophic balance between pressure gradient, Coriolis force, wind stress and friction driving the circulation. Parameters including water depth, natural dissipation rate and wind stress are calibrated in the model so that the model can reproduce reasonable flow properties including volume flux and energy flux. To represent flow dissipation due to turbines additional turbine drag coefficient is formulated and included in the model. Secondly, to determine the reasonableness of the total power

  3. Operational Utilization of High Resolution Ocean Surface Wind Vectors (25km or better) in the Marine Forecasting Environment

    National Research Council Canada - National Science Library

    Chang, Paul S; Sienkiewicz, Joseph; Knabb, Richard; Gaiser, Peter W; Long, David G; Freeberg, Mark

    2005-01-01

    .... This work will build upon an ongoing effort to quantify the impacts of QuikSCAT ocean vector wind data in the operational short-term warnings and forecasts issued by the NWS Ocean Prediction Center (OPC...

  4. Operational Utilization of High Resolution Ocean Surface Wind Vectors (25km or Better) in the Marine Forecasting Environment

    National Research Council Canada - National Science Library

    Chang, Paul S; Sienkiewicz, Joseph; Knabb, Richard; Gaiser, Peter W; Long, David G; Freeberg, Mark

    2004-01-01

    .... This work will build upon an ongoing effort to quantify the impacts of QuikSCAT ocean vector wind data in the operational short-term warnings and forecasts issued by the NWS Ocean Prediction Center (OPC...

  5. On the Use of Coupled Wind, Wave, and Current Fields in the Simulation of Loads on Bottom-Supported Offshore Wind Turbines during Hurricanes: March 2012 - September 2015

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Eungsoo [Univ. of Texas, Austin, TX (United States); Manuel, Lance [Univ. of Texas, Austin, TX (United States); Curcic, Milan [Univ. of Miami, Coral Gables, FL (United States); Chen, Shuyi S. [Univ. of Miami, Coral Gables, FL (United States); Phillips, Caleb [National Renewable Energy Lab. (NREL), Golden, CO (United States); Veers, Paul [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2016-06-01

    In the United States, potential offshore wind plant sites have been identified along the Atlantic seaboard and in the Gulf of Mexico. It is imperative that we define external conditions associated with hurricanes and severe winter storms and consider load cases for which wind turbines may need to be designed. We selected two hurricanes, Ike (2008) and Sandy (2012), and investigated the effect these tropical storms would have on bottom-supported offshore wind turbines that were hypothetically in or close to their path as they made landfall. For realistic turbine loads assessment, it is important that the coupled influences of the changing wind, wave, and current fields are simulated throughout the evolution of the hurricanes. We employed a coupled model--specifically, the University of Miami Coupled Model (UMCM)--that integrates atmospheric, wave, and ocean components to produce needed wind, wave, and current data. The wind data are used to generate appropriate vertical wind profiles and full wind velocity fields including turbulence; the current field over the water column is obtained by interpolated discrete output current data; and short-crested irregular second-order waves are simulated using output directional wave spectra from the coupled model. We studied two monopile-supported offshore wind turbines sited in 20 meters of water in the Gulf of Mexico to estimate loads during Hurricane Ike, and a jacket space-frame platform-supported offshore wind turbine sited in 50 meters of water in the mid-Atlantic region to estimate loads during Hurricane Sandy. In this report we discuss in detail how the simulated hurricane wind, wave, and current output data are used in turbine loads studies. In addition, important characteristics of the external conditions are studied, including the relative importance of swell versus wind seas, aerodynamic versus hydrodynamic forces, current velocity effects, yaw control options for the turbine, hydrodynamic drag versus inertia forces

  6. Microwave Remote Sensing Modeling of Ocean Surface Salinity and Winds Using an Empirical Sea Surface Spectrum

    Science.gov (United States)

    Yueh, Simon H.

    2004-01-01

    Active and passive microwave remote sensing techniques have been investigated for the remote sensing of ocean surface wind and salinity. We revised an ocean surface spectrum using the CMOD-5 geophysical model function (GMF) for the European Remote Sensing (ERS) C-band scatterometer and the Ku-band GMF for the NASA SeaWinds scatterometer. The predictions of microwave brightness temperatures from this model agree well with satellite, aircraft and tower-based microwave radiometer data. This suggests that the impact of surface roughness on microwave brightness temperatures and radar scattering coefficients of sea surfaces can be consistently characterized by a roughness spectrum, providing physical basis for using combined active and passive remote sensing techniques for ocean surface wind and salinity remote sensing.

  7. Calibration Performance and Capabilities of the New Compact Ocean Wind Vector Radiometer System

    Science.gov (United States)

    Brown, S. T.; Focardi, P.; Kitiyakara, A.; Maiwald, F.; Montes, O.; Padmanabhan, S.; Redick, R.; Russell, D.; Wincentsen, J.

    2014-12-01

    The paper describes performance and capabilities of a new satellite conically imaging microwave radiometer system, the Compact Ocean Wind Vector Radiometer (COWVR), being built by the Jet Propulsion Laboratory (JPL) for an Air Force demonstration mission. COWVR is an 18-34 GHz fully polarimetric radiometer designed to provide measurements of ocean vector winds with an accuracy that meets or exceeds that provided by WindSat, but using a simpler design which has both calibration and cost advantages. Heritage conical radiometer systems, such as WindSat, AMSR, GMI or SSMI(S), all have a similar overall architecture and have exhibited significant intra-channel and inter-sensor calibration biases, due in part to the relative independence of the radiometers between the different polarizations and frequencies in the system. The COWVR system uses a broadband compact hybrid combining architecture and Electronic Polarization Basis Rotation to minimize the number of free calibration parameters between polarization and frequencies, as well as providing a definitive calibration reference from the modulation of the mean polarized signal from the Earth. This second calibration advantage arises because the sensor modulates the incoming polarized signal at the input antenna aperture in a known way based only on the instrument geometry which forces relative calibration consistency between the polarimetric channels of the sensor and provides a gain and offset calibration independent of a model or other ancillary data source, which has typically been a weakness in the calibration and inter-calibration of heritage microwave sensors. This paper will give a description of the COWVR instrument and an overview of the technology demonstration mission. We will discuss the overall calibration approach for this system, its advantages over existing systems and how many of the calibration issues that impact existing satellite radiometers can be eliminated in future operational systems based on

  8. Secondary current properties generated by wind-induced water waves in experimental conditions

    Directory of Open Access Journals (Sweden)

    Michio Sanjou

    2014-06-01

    Full Text Available Secondary currents such as the Langmuir circulation are of high interest in natural rivers and the ocean because they have striking impacts on scour, sedimentation, and mass transport. Basic characteristics have been well-studied in straight open-channel flows. However, little is known regarding secondary circulation induced by wind waves. The presented study describes the generation properties of wind waves observed in the laboratory tank. Wind-induced water waves are known to produce large scale circulations. The phenomenon is observed together with high-speed and low-speed streaks, convergence and divergence zones, respectively. Therefore, it is important to determine the hydrodynamic properties of secondary currents for wind-induced water waves within rivers and lakes. In this study, using two high-speed CMOS cameras, stereoscopic particle image velocimetry (PIV measurements were conducted in order to reveal the distribution of all three components of velocity vectors. The experiments allowed us to investigate the three-dimensional turbulent structure under water waves and the generation mechanism of large-scale circulations. Additionally, a third CMOS camera was used to measure the spanwise profile of thefree-surface elevation. The time-series of velocity components and the free-surface were obtained simultaneously. From our experiments, free-surface variations were found to influence the instantaneous velocity distributions of the cross-sectional plane. We also considered thegeneration process by the phase analysis related to gravity waves and compared the contribution of the apparent stress.

  9. Turbulent kinetic energy of the ocean winds over the Kuroshio Extension from QuikSCAT winds (1999-2009)

    Science.gov (United States)

    Yu, Kai; Dong, Changming; King, Gregory P.

    2017-06-01

    We investigate mesoscale turbulence (10-1000 km) in the ocean winds over the Kuroshio Extension (28°N-40°N, 140°E-180°E) using the QuikSCAT data set (November 1999 to October 2009). We calculate the second (Djj) and third-order structure functions (Djjj) and the spatial variance (Vj) as a function of scale r (j=L,T denotes, respectively, the longitudinal (divergent) and transverse (vortical) component). The most interesting results of the analysis follow. Although both Vj>(r>) and Djj>(r>) measure the turbulent kinetic energy (TKE), we find that Vj>(r>) is the more robust measure. The spatial variance density (dVj/dr) has a broad peak near 450 km (close to the midlatitude Rossby radius of deformation). On interannual time scales, TKE correlates well with the El Niño 3.4 index. According to turbulence theory, the kinetic energy cascades downscale (upscale) if DLLL>(r>) (also skewness SL=DLLL/DLL3/2) is negative (positive). Our results for the Kuroshio Extension are consistent with a downscale cascade (indicating convergence dominates). Furthermore, classical turbulence theory predicts that SL=-0.3 and independent of r; however, we find SL varies strongly with r, from -4 at small scales to -0.3 at large scales. This nonclassical behavior implies strong-scale interaction, which we attribute to the rapid, and sometimes explosive, growth of storms in the region through baroclinic instability. Finally, we find that ST (a measure of cyclonic/anticyclonic asymmetry) is positive (cyclonic) and also varies strongly with r, from 4 at small scales to 0.5 at large scales. New turbulence models are needed to explain these results, and that will benefit Weather Prediction and climate modeling.Plain Language SummaryThe turbulent winds near the ocean surface give rise to air-sea heat and momentum exchange. The turbulence is caused by convective processes - processes generated at weather fronts, in squalls, tropical disturbances and extra-tropical cyclones. In order to improve

  10. Ocean Wind and Wave Measurements Using X-Band Marine Radar: A Comprehensive Review

    Directory of Open Access Journals (Sweden)

    Weimin Huang

    2017-12-01

    Full Text Available Ocean wind and wave parameters can be measured by in-situ sensors such as anemometers and buoys. Since the 1980s, X-band marine radar has evolved as one of the remote sensing instruments for such purposes since its sea surface images contain considerable wind and wave information. The maturity and accuracy of X-band marine radar wind and wave measurements have already enabled relevant commercial products to be used in real-world applications. The goal of this paper is to provide a comprehensive review of the state of the art algorithms for ocean wind and wave information extraction from X-band marine radar data. Wind measurements are mainly based on the dependence of radar image intensities on wind direction and speed. Wave parameters can be obtained from radar-derived wave spectra or radar image textures for non-coherent radar and from surface radial velocity for coherent radar. In this review, the principles of the methodologies are described, the performances are compared, and the pros and cons are discussed. Specifically, recent developments for wind and wave measurements are highlighted. These include the mitigation of rain effects on wind measurements and wave height estimation without external calibrations. Finally, remaining challenges and future trends are discussed.

  11. Origins of wind-driven intraseasonal sea level variations in the North Indian Ocean coastal waveguide

    Digital Repository Service at National Institute of Oceanography (India)

    Suresh, I.; Vialard, J.; Lengaigne, M.; Han, W.; McCreary, J.P.; Durand, F.; Muraleedharan, P.M.

    over the 30°S−30°N, 30°E−110°E domain, with a coastline determined from the 200-m isobath. The model is forced by intraseasonal (20−150-day filtered) daily QuikSCAT wind-stresses (available from http://cersat/ifremer.fr/data/) from August, 1999... to October, 2009. Several studies indicate that this wind-stress product yields a realistic intraseasonal oceanic response in the equatorial Indian Ocean [e.g., Sengupta et al., 2007; Nagura and McPhaden, 2012]. We show results obtained using 5 baroclinic...

  12. Ocean Science for Decision-Making: Current Activities of the National Research Council's Ocean Studies Board

    Science.gov (United States)

    Roberts, S.; Glickson, D.; Mengelt, C.; Forrest, S.; Waddell, K.

    2012-12-01

    The National Research Council is a private, nonprofit organization chartered by Congress in 1916 as an expansion of the U.S. National Academy of Sciences. Its mission is to improve the use of science in government decision making and public policy, increase public understanding, and promote the acquisition and dissemination of knowledge in matters involving science, engineering, technology, and health. Within the National Research Council, the Ocean Studies Board (OSB) mission is to explore the science, policies, and infrastructure needed to understand, manage, and conserve coastal and marine environments and resources. OSB undertakes studies and workshops on emerging scientific and policy issues at the request of federal agencies, Congress, and others; provides program reviews and guidance; and facilitates communication on oceanographic issues among different sectors. OSB also serves as the U.S. National Committee to the international, nongovernmental Scientific Committee on Oceanic Research (SCOR). OSB has produced reports on a wide range of topics of interest to researchers and educators, the federal government, the non-profit sector, and industry. Recent reports have focused on ecosystem services in the Gulf of Mexico after the Deepwater Horizon oil spill, sea level rise on the U.S. west coast, scientific ocean drilling needs and accomplishments, requirements for sustained ocean color measurements, critical infrastructure for ocean research, tsunami warning and preparedness, ocean acidification, and marine and hydrokinetic power resource assessments. Studies that are currently underway include responding to oil spills in the Arctic, evaluating the effectiveness of fishery stock rebuilding plans, and reviewing the National Ocean Acidification Research Plan. OSB plays an important role in helping create policy decisions and disseminating important information regarding various aspects of ocean science.

  13. Wind speed, wind direction, air temperature, wave energy spectra, significant wave height, dominant wave period and direction, peak wave period and direction, currents, temperature, conductivity, pressure, sigma-theta, river level, sonar readings, and backscatter data collected at Myrtle Beach in the North Atlantic Ocean from instruments deployed on MOORINGS using platforms NOAA Ship NANCY FOSTER and RV DAN MOORE from 2003-10-01 to 2004-05-01 (NODC Accession 0066109)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These bottom current, wave and associated observations were collected as part of a larger study to understand the physical processes that control the transport of...

  14. Spectral analysis of wind field in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Rashmi, R.; Samiksha, S.V.; Polnikov, V.; Pogarskii, F.; Sudheesh, K.; Vethamony, P.

    inhomogeneity in the analysed wind fields Spectral analysis of the time series (extracted at the centre of each zone) was performed using the auto-regression analysis based on the Yule-Walker equations Frequency spectra show distinct annual variations at all...

  15. Ocean Wind and Wave Measurements Using X-Band Marine Radar: A Comprehensive Review

    OpenAIRE

    Weimin Huang; Xinlong Liu; Eric W. Gill

    2017-01-01

    Ocean wind and wave parameters can be measured by in-situ sensors such as anemometers and buoys. Since the 1980s, X-band marine radar has evolved as one of the remote sensing instruments for such purposes since its sea surface images contain considerable wind and wave information. The maturity and accuracy of X-band marine radar wind and wave measurements have already enabled relevant commercial products to be used in real-world applications. The goal of this paper is to provide a comprehensi...

  16. Simulation of the Impact of New Aircraft-and Satellite-based Ocean Surface Wind Measurements on Wind Analyses and Numerical Forecasts

    Science.gov (United States)

    Miller, TImothy; Atlas, Robert; Black, Peter; Chen, Shuyi; Jones, Linwood; Ruf, Chris; Uhlhorn, Eric; Gamache, John; Amarin, Ruba; El-Nimri, Salem; hide

    2010-01-01

    The Hurricane Imaging Radiometer (HIRAD) is a new airborne microwave remote sensor for hurricane observations that is currently under development by NASA Marshall Space Flight Center, NOAA Hurricane Research Division, the University of Central Florida and the University of Michigan. HIRAD is being designed to enhance the realtime airborne ocean surface winds observation capabilities of NOAA and USAF Weather Squadron hurricane hunter aircraft currently using the operational airborne Stepped Frequency Microwave Radiometer (SFMR). Unlike SFMR, which measures wind speed and rain rate along the ground track directly beneath the aircraft, HIRAD will provide images of the surface wind and rain field over a wide swath (approx. 3 x the aircraft altitude). The present paper describes a set of Observing System Simulation Experiments (OSSEs) in which measurements from the new instrument as well as those from existing instruments (air, surface, and space-based) are simulated from the output of a detailed numerical model, and those results are used to construct H*Wind analyses, a product of the Hurricane Research Division of NOAA s Atlantic Oceanographic and Meteorological Laboratory. Evaluations will be presented on the impact of the HIRAD instrument on H*Wind analyses, both in terms of adding it to the full suite of current measurements, as well as using it to replace instrument(s) that may not be functioning at the future time the HIRAD instrument is implemented. Also shown will be preliminary results of numerical weather prediction OSSEs in which the impact of the addition of HIRAD observations to the initial state on numerical forecasts of the hurricane intensity and structure is assessed.

  17. Wind energy input into the upper ocean over a lengthening open water season

    Science.gov (United States)

    Mahoney, A. R.; Rolph, R.; Walsh, J. E.

    2017-12-01

    Wind energy input into the ocean has important consequences for upper ocean mixing, heat and gas exchange, and air-sea momentum transfer. In the Arctic, the open water season is increasing and extending further into the fall storm season, allowing for more wind energy input into the water column. The rate at which the delayed freeze-up timing extends into fall storm season is an important metric to evaluate because the expanding overlap between the open water period and storm season could contribute a significant amount of wind energy into the water column in a relatively short period of time. We have shown that time-integrated wind speeds over open water in the Chukchi Sea and southern Beaufort region have increased since 1979 through 2014. An integrated wind energy input value is calculated for each year in this domain over the open water season, as well as for periods over partial concentrations of ice cover. Spatial variation of this integrated wind energy is shown along the Alaskan coastline, which can have implications for different rates of coastal erosion. Spatial correlation between average wind speed over open water and open water season length from 1979-2014 show positive values in the southern Beaufort, but negative values in the northern Chukchi. This suggests possible differences in the role of the ocean on open water season length depending on region. We speculate that the warm Pacific water outflow plays a more dominant role in extending the open water season length in the northern Chukchi when compared to the southern Beaufort, and might help explain why we can show there is a relatively longer open water season length there. The negative and positive correlations in wind speeds over open water and open water season length might also be explained by oceanic changes tending to operate on longer timescales than the atmosphere. Seasonal timescales of wind events such as regional differences in overlap of the extended open water season due to regional

  18. Wind direction over the ocean determined by an airborne, imaging, polarimetric radiometer system

    DEFF Research Database (Denmark)

    Laursen, Brian; Skou, Niels

    2001-01-01

    The speed and direction of winds over the ocean can be determined by polarimetric radiometers. This has been established by theoretical work and demonstrated experimentally using airborne radiometers carrying out circle flights and thus measuring the full 360° azimuthal response from the sea surf...

  19. Westerly Winds and the Southern Ocean CO2 Sink Since the Last Glacial-Interglacial Transition

    Science.gov (United States)

    Hodgson, D. A.; Saunders, K. M.; Roberts, S. J.; Perren, B.; Butz, C.; Sime, L. C.; Davies, S. J.; Grosjean, M.

    2017-12-01

    The capacity of the Southern Ocean carbon sink is partly controlled by the Southern Hemisphere westerly winds (SHW) and sea ice. These regulate the upwelling of dissolved carbon-rich deep water to Antarctic surface waters, determine the surface area for air-sea gas exchange and therefore modulate the net uptake of atmospheric CO2. Some models have proposed that strengthened SHW will result in a weakening of the Southern Ocean CO2 sink. If these models are correct, then one would expect that reconstructions of changes in SHW intensity on centennial to millennial timescales would show clear links with Antarctic ice core and Southern Ocean marine geological records of atmospheric CO2, temperature and sea ice. Here, we present a 12,300 year reconstruction of past wind strength based on three independent proxies that track the changing inputs of sea salt aerosols and minerogenic particles into lake sediments on sub-Antarctic Macquarie Island. The proxies are consistent in showing that periods of high wind intensity corresponded with the increase in CO2 across the late Last Glacial-Interglacial Transition and in the last 7,000 years, suggesting that the winds have contributed to the long term outgassing of CO2 from the ocean during these periods.

  20. Monthly mean wind stress along the coast of the north Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Shetye, S.R.; Shenoi, S.S.C.; Antony, M.K.; Krishnakumar, V.

    Monthly-mean wind stress and its longshore and offshore components have been computed using the bulk aerodynamic method for each of a string of 36 two-degree-latitude by two-degree-longitude squares along the coast of the north Indian Ocean...

  1. Recent studies on wind seas and swells in the Indian Ocean: A review

    Digital Repository Service at National Institute of Oceanography (India)

    Vethamony, P.; Rashmi, R.; Samiksha, S.V.; Aboobacker, V.M.

    , decrease in swell period and a common propagation direction (northwest) for wind seas and swells Also the swells generated at 40 degrees S, propagate in the north Indian Ocean, and enter in the Bay of Bengal than the Arabian Sea During fair weather season...

  2. Detailed ocean current maps may lie over the horizon

    Science.gov (United States)

    Carlowicz, Michael

    In another case of military swords being turned into scientific plowshares, two American researchers have used radar systems once designed to detect Soviet planes during the Cold War to map open-ocean currents instead.In the name of science, Thomas Georges and Jack Harlan of NOAA's Environmental Technology Laboratory borrowed some time last summer on the U.S. Navy's over-the-horizon (OTH) radar systems in both Virginia and Texas. Training the radars on the waters off of the southern coast of Florida, the researchers gathered enough data to deduce the surface motion of two 70,000 km2 swatches of the Caribbean Sea and Gulf of Mexico. By bouncing 5-28 MHz radio waves off the ionosphere down to the sea surface and back, the researchers were able to derive the characteristics of the ocean surface from Bragg backscatter resonance.

  3. Current direction, marine toxic substances, and wind wave spectra data from moored current meter casts and other instruments in the Gulf of Mexico as part of the Brine Disposal project, 1977-09-15 to 1979-06-30 (NODC Accession 7900295)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction, marine toxic substances, and wind wave spectra data were collected using moored current meter casts and other instruments in the Gulf of Mexico...

  4. Current direction, chemical, benthic organisms, and wind wave spectra data from moored current meter casts and other instruments in the Gulf of Mexico as part of the Brine Disposal project, 1977-10-14 to 1979-08-24 (NODC Accession 7900335)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction, chemical, benthic organisms, and wind direction data were collected using moored current meter casts and other instruments in the Gulf of Mexico...

  5. Current direction, marine toxic substances, and wind wave spectra data from moored current meter casts and other instruments in the Gulf of Mexico as part of the Brine Disposal project, 1977-12-22 to 1979-09-30 (NODC Accession 7900336)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction, marine toxic substances, and wind wave spectra data were collected using moored current meter casts and other instruments in the Gulf of Mexico...

  6. HF Radar Observations of Current, Wave and Wind Parameters in the South Australian Gulf

    Science.gov (United States)

    Middleditch, A.; Cosoli, S.

    2016-12-01

    The Australian Coastal Ocean Radar Network (ACORN) has been measuring metocean parameters from an array of HF radar systems since 2007. Current, wave and wind measurements from a WERA phased-array radar system in the South Australian Gulf are evaluated using current meter, wave buoy and weather station data over a 12-month period. The spatial and temporal scales of the radar deployment have been configured for the measurement of surface currents from the first order backscatter spectra. Quality control procedures are applied to the radar currents that relate to the geometric configurations, statistical properties, and diagnostic variables provided by the analysis software. Wave measurements are obtained through an iterative inversion algorithm that provides an estimate of the directional frequency spectrum. The standard static configurations and data sampling strategies are not optimised for waves and so additional signal processing steps need to be implemented in order to provide reliable estimates. These techniques are currently only applied in offline mode but a real-time approach is in development. Improvements in the quality of extracted wave data are found through increased averaging of the raw radar data but the impact of temporal non-stationarity and spatial inhomogeneities in the WERA measurement region needs to be taken into account. Validations of wind direction data from a weather station on Neptune Island show the potential of using HF radar to combat the spread of bushfires in South Australia.

  7. Twenty-first century wave climate projections for Ireland and surface winds in the North Atlantic Ocean

    Science.gov (United States)

    Gallagher, Sarah; Gleeson, Emily; Tiron, Roxana; McGrath, Ray; Dias, Frédéric

    2016-04-01

    Ireland has a highly energetic wave and wind climate, and is therefore uniquely placed in terms of its ocean renewable energy resource. The socio-economic importance of the marine resource to Ireland makes it critical to quantify how the wave and wind climate may change in the future due to global climate change. Projected changes in winds, ocean waves and the frequency and severity of extreme weather events should be carefully assessed for long-term marine and coastal planning. We derived an ensemble of future wave climate projections for Ireland using the EC-Earth global climate model and the WAVEWATCH III® wave model, by comparing the future 30-year period 2070-2099 to the period 1980-2009 for the RCP4.5 and the RCP8.5 forcing scenarios. This dataset is currently the highest resolution wave projection dataset available for Ireland. The EC-Earth ensemble predicts decreases in mean (up to 2 % for RCP4.5 and up to 3.5 % for RCP8.5) 10 m wind speeds over the North Atlantic Ocean (5-75° N, 0-80° W) by the end of the century, which will consequently affect swell generation for the Irish wave climate. The WAVEWATCH III® model predicts an overall decrease in annual and seasonal mean significant wave heights around Ireland, with the largest decreases in summer (up to 15 %) and winter (up to 10 %) for RCP8.5. Projected decreases in mean significant wave heights for spring and autumn were found to be small for both forcing scenarios (less than 5 %), with no significant decrease found for RCP4.5 off the west coast in those seasons.

  8. Assessment of the importance of the current-wave coupling in the shelf ocean forecasts

    Directory of Open Access Journals (Sweden)

    G. Jordà

    2007-07-01

    Full Text Available The effects of wave-current interactions on shelf ocean forecasts is investigated in the framework of the MFSTEP (Mediterranean Forecasting System Project Towards Enviromental Predictions project. A one way sequential coupling approach is adopted to link the wave model (WAM to the circulation model (SYMPHONIE. The coupling of waves and currents has been done considering four main processes: wave refraction due to currents, surface wind drag and bottom drag modifications due to waves, and the wave induced mass flux. The coupled modelling system is implemented in the southern Catalan shelf (NW Mediterranean, a region with characteristics similar to most of the Mediterranean shelves. The sensitivity experiments are run in a typical operational configuration. The wave refraction by currents seems to be not very relevant in a microtidal context such as the western Mediterranean. The main effect of waves on current forecasts is through the modification of the wind drag. The Stokes drift also plays a significant role due to its spatial and temporal characteristics. Finally, the enhanced bottom friction is just noticeable in the inner shelf.

  9. Turbulence Simulation of Laboratory Wind-Wave Interaction in High Winds and Upscaling to Ocean Conditions

    Science.gov (United States)

    2016-12-22

    mean wind profile, and a minor reduction in the form drag fraction. This supports recent theoretical perspectives that propose very differing... turnover times. For the results, wind and pressure fields are made dimensionless by (u*, u* 2 ) and all lengths are made dimensionless by  where... turnover times (~ 50) owing to the reduction in the timestep on the fine grid. We found the fine mesh runs were similar in character to the coarse mesh

  10. Current Status and Challenges in Wind Energy Assessment

    DEFF Research Database (Denmark)

    Gryning, Sven-Erik; Badger, Jake; Hahmann, Andrea N.

    2014-01-01

    Here we discuss the status and challenges in the development of atlases for the assessment of the regional and global wind resources. The text more specifically describes a methodology that is under development at DTU Wind Energy in Denmark. As the wind assessment is based on mesoscale modelling......, some of the specific challenges in mesoscale modelling for wind energy purposes are discussed such as wind profiles and long-term statistics of the wind speed time series. Solutions to these challenges will help secure an economic and effective deployment of wind energy....

  11. Buoy perspective of a high-resolution global ocean vector wind analysis constructed from passive radiometers and active scatterometers (1987-present)

    Science.gov (United States)

    Yu, Lisan; Jin, Xiangze

    2012-11-01

    The study used 126 buoy time series as a benchmark to evaluate a satellite-based daily, 0.25-degree gridded global ocean surface vector wind analysis developed by the Objectively Analyzed airs-sea Fluxes (OAFlux) project. The OAFlux winds were produced from synthesizing wind speed and direction retrievals from 12 sensors acquired during the satellite era from July 1987 onward. The 12 sensors included scatterometers (QuikSCAT and ASCAT), passive microwave radiometers (AMSRE, SSMI and SSMIS series), and the passive polarimetric microwave radiometer from WindSat. Accuracy and consistency of the OAFlux time series are the key issues examined here. A total of 168,836 daily buoy measurements were assembled from 126 buoys, including both active and archive sites deployed during 1988-2010. With 106 buoys from the tropical array network, the buoy winds are a good reference for wind speeds in low and mid-range. The buoy comparison shows that OAFlux wind speed has a mean difference of -0.13 ms-1 and an RMS difference of 0.71 ms-1, and wind direction has a mean difference of -0.55 degree and an RMS difference of 17 degrees. Vector correlation of OAFlux and buoy winds is of 0.9 and higher over almost all the sites. Influence of surface currents on the OAFlux/buoy mean difference pattern is displayed in the tropical Pacific, with higher (lower) OAFlux wind speed in regions where wind and current have the opposite (same) sign. Improved representation of daily wind variability by the OAFlux synthesis is suggested, and a decadal signal in global wind speed is evident.

  12. Reducing AC-Winding Losses in High-Current High-Power Inductors

    DEFF Research Database (Denmark)

    Nymand, Morten; Madawala, Udaya K.; Andersen, Michael Andreas E.

    2009-01-01

    Foil windings are preferable in high-current high-power inductors to realize compact designs and to reduce dc-current losses. At high frequency, however, proximity effect will cause very significant increase in ac resistance in multi-layer windings, and lead to high ac winding losses. This paper...... designed with low ac resistance and leakage inductance to carry the ac current while the outer winding is designed for the large dc current. Detailed analysis and design of a 350 A, 10 kW inductor with the proposed technique are presented with discussions. Experimental results of a prototype 350 A inductor...... presents design, analysis and experimental verification of a two winding technique, which significantly reduces ac winding losses without compromising dc losses. The technique uses an inner auxiliary winding, which is connected in parallel with an outer main winding. The auxiliary winding is optimally...

  13. Short-Circuit Current Analysis for DFIG Wind Farm Considering the Action of a Crowbar

    Directory of Open Access Journals (Sweden)

    Yan Hong Yuan

    2018-02-01

    Full Text Available With the increasing capacity of wind farms integrated into the power grid, the short-circuit current analysis for wind farms becomes more and more important. Since the wind turbine is usually integrated into the power grid via power electronic devices, the “crowbar” is installed in the wind turbine to protect the power electronic devices and to improve the fault ride through capability. The impact of the crowbar has to be considered during the short-circuit current analysis for the wind farm. In order to fully analyze the short-circuit current characteristics of a wind farm, the short-circuit currents for a doubly-fed induction generator (DFIG wind turbine under symmetrical and asymmetrical faults considering the crowbar action characteristic are derived firstly. Then the action situation of the crowbar of a DFIG wind turbine is studied and the action area curve is obtained. Taking the crowbar action, or not, as the grouping criterion, wind turbines in the wind farm are divided into two groups, and the wind farm is aggregated into two equivalent wind turbines. Using the equivalent model, the short-circuit current of a wind farm can be calculated accurately. Finally, simulations are performed in MATLAB/Simulink which is the commercial math software produced by the MathWorks company in Natick, Massachusetts, the United States to verify the proposed short-circuit current calculation method for the DFIG wind farm.

  14. Practical Application of Eddy Currents Generated by Wind

    Energy Technology Data Exchange (ETDEWEB)

    Dirba, I; Kleperis, J, E-mail: imants.dirba@gmail.com [Institute of Solid State Physics of University of Latvia, 8 Kengaraga Street, Riga, LV-1063 (Latvia)

    2011-06-23

    When a conductive material is subjected to time-varying magnetic fluxes, eddy (Foucault) currents are generated in it and magnetic field of opposite polarity as the applied one arises. Due to the internal resistance of the conductive material, the eddy currents will be dissipated into heat (Joule heating). Conventional domestic water heaters utilize gas burners or electric resistance heating elements to heat the water in the tank and substantial part of the energy to use for it is wasted. In this paper the origin of electromagnetic induction heat generated by wind turbine in special heat exchange camera connected to water boiler is discussed and material evaluation performed using mathematical modelling (comparing the 2D finite element model with analytical and numerical calculation results).

  15. Practical Application of Eddy Currents Generated by Wind

    International Nuclear Information System (INIS)

    Dirba, I; Kleperis, J

    2011-01-01

    When a conductive material is subjected to time-varying magnetic fluxes, eddy (Foucault) currents are generated in it and magnetic field of opposite polarity as the applied one arises. Due to the internal resistance of the conductive material, the eddy currents will be dissipated into heat (Joule heating). Conventional domestic water heaters utilize gas burners or electric resistance heating elements to heat the water in the tank and substantial part of the energy to use for it is wasted. In this paper the origin of electromagnetic induction heat generated by wind turbine in special heat exchange camera connected to water boiler is discussed and material evaluation performed using mathematical modelling (comparing the 2D finite element model with analytical and numerical calculation results).

  16. Practical Application of Eddy Currents Generated by Wind

    Science.gov (United States)

    Dirba, I.; Kleperis, J.

    2011-06-01

    When a conductive material is subjected to time-varying magnetic fluxes, eddy (Foucault) currents are generated in it and magnetic field of opposite polarity as the applied one arises. Due to the internal resistance of the conductive material, the eddy currents will be dissipated into heat (Joule heating). Conventional domestic water heaters utilize gas burners or electric resistance heating elements to heat the water in the tank and substantial part of the energy to use for it is wasted. In this paper the origin of electromagnetic induction heat generated by wind turbine in special heat exchange camera connected to water boiler is discussed and material evaluation performed using mathematical modelling (comparing the 2D finite element model with analytical and numerical calculation results).

  17. Predictive Understanding of the Oceans' Wind-Driven Circulation on Interdecadal Time Scales

    Energy Technology Data Exchange (ETDEWEB)

    Ghil, Michael [Univ. of California, Los Angeles, CA (United States). Dept. of Atmospheric and Oceanic Sciences and IGPP; Temam, Roger [Indiana Univ., Bloomington, IN (United States). Dept. of Mathematics; Feliks, Y. [IIBR (France); Simonnet, E. [INLN (France); Tachim-Medjo, T. [Florida International Univ. (FIU), Miami, FL (United States)

    2008-09-30

    The goal of this project was to obtain a predictive understanding of a major component of the climate system's interdecadal variability: the oceans' wind-driven circulation. To do so, we developed and applied advanced computational and statistical methods to the problem of climate variability and climate change. The methodology was developed first for models of intermediate complexity, such as the quasi-geostrophic and the primitive equations, which describe the wind-driven, near-surface flow in mid-latitude ocean basins. Our computational work consisted in developing efficient multi-level methods to simulate this flow and study its dependence on physically relevant parameters. Our oceanographic and climate work consisted in applying these methods to study the bifurcations in the wind-driven circulation and their relevance to the flows observed at present and those that might occur in a warmer climate. Both aspects of the work are crucial for the efficient treatment of large-scale, eddy-resolving numerical simulations of the oceans and an increased understanding and better prediction of climate change. Considerable progress has been achieved in understanding ocean-atmosphere interaction in the mid-latitudes. An important by-product of this research is a novel approach to explaining the North Atlantic Oscillation.

  18. Competition between ocean carbon pumps in simulations with varying Southern Hemisphere westerly wind forcing

    Science.gov (United States)

    Huiskamp, W. N.; Meissner, K. J.; d'Orgeville, M.

    2016-06-01

    We analyse the impact of migration and strength of Southern Hemisphere westerly winds on the ocean carbon cycle in a systematic sensitivity study with the University of Victoria Earth System Climate Model. We find that changes in the biological pump are mainly driven by changes in ocean residence times while changes in export production are negligible. Changes in the biological and physical pumps are always of opposite sign; with the physical pump being dominant for southward shifts and the biological pump being dominant for northward shifts. Furthermore, changes in the Pacific Ocean carbon budget dictate the overall changes in global marine and atmospheric carbon. Overall, atmospheric hbox {CO}_2 increases (and Δ ^{14}hbox {C} decreases) for northward shifts or a strengthening in wind forcing. The opposite is true for a southward shift or a weakening in wind forcing. Combining forcings (shift and intensity change) results in a combination of their impacts with the direction of the shift being the first order forcing. The terrestrial carbon reservoir absorbs (releases) 50-70 % of the net oceanic carbon loss (increase), counterbalancing the effect on atmospheric hbox {CO}_2.

  19. Advection by ocean currents modifies phytoplankton size structure.

    Science.gov (United States)

    Font-Muñoz, Joan S; Jordi, Antoni; Tuval, Idan; Arrieta, Jorge; Anglès, Sílvia; Basterretxea, Gotzon

    2017-05-01

    Advection by ocean currents modifies phytoplankton size structure at small scales (1-10 cm) by aggregating cells in different regions of the flow depending on their size. This effect is caused by the inertia of the cells relative to the displaced fluid. It is considered that, at larger scales (greater than or equal to 1 km), biological processes regulate the heterogeneity in size structure. Here, we provide observational evidence of heterogeneity in phytoplankton size structure driven by ocean currents at relatively large scales (1-10 km). Our results reveal changes in the phytoplankton size distribution associated with the coastal circulation patterns. A numerical model that incorporates the inertial properties of phytoplankton confirms the role of advection on the distribution of phytoplankton according to their size except in areas with enhanced nutrient inputs where phytoplankton dynamics is ruled by other processes. The observed preferential concentration mechanism has important ecological consequences that range from the phytoplankton level to the whole ecosystem. © 2017 The Author(s).

  20. Temperature, wind direction, and salinity data from moored current meter casts in the Gulf of Mexico during the Brine Disposal project, 01 December 1980 - 01 December 1980 (NODC Accession 8100457)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature, wind direction, and salinity data were collected using moored current meter casts in the Gulf of Mexico from December 1, 1980 to December 1, 1980. Data...

  1. Temperature, wind direction, and salinity data from moored current meter casts in the Gulf of Mexico during the Brine Disposal project, 01 January 1981 - 01 January 1981 (NODC Accession 8100474)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature, wind direction, and salinity data were collected using moored current meter casts in the Gulf of Mexico from January 1, 1981 to January 1, 1981. Data...

  2. Wind wave spectra and other data from moored current meter casts and other instruments in the Gulf of Mexico as part of the Brine Disposal project, 1979-09-22 to 1980-05-01 (NODC Accession 8000462)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Wind wave spectra and other data were collected using moored current meter casts and other instruments in the Gulf of Mexico from September 22, 1979 to May 1, 1980....

  3. HORIZONTAL AXIS MARINE CURRENT TURBINE DESIGN FOR WIND-ELECTRIC HYBRID SAILING BOAT

    Directory of Open Access Journals (Sweden)

    Serkan Ekinci

    2017-01-01

    Full Text Available In recent decades, the number of theoretical studies and applications on electric power production from renewable sources such as wind, solar, sea and tidal flows, has been increasing rapidly. Marine Current Turbines (MCTs, among the power turbines, produce power from alternating flows and are a means of power production even at lower flow rates in oceans and seas. In this study, while maintaining functional requirements, an initial and detailed design (mechanic and hydrodynamic, of an MCT fixed on a sailing boat and at sail which extracts power from the flow around the boat, is undertaken. In the design stages, for analysis and optimization of the marine turbine blade design, the Momentum Blade Element Method is utilized. The Horizontal Axis Marine Turbine (HAMT, determined by the initial and mechanical design, is illustrated with its components included. Computational fluid dynamics (CFD analyses, covering turbine pod geometry at required flow rates and turbine speeds are performed. These analyses are performed very close to real conditions, considering sailing with and without the turbine running (on and off states. The alternator is determined from the results, and the final design which meets the design requirements, is obtained. As a result, a user friendly and innovative turbine design for sail boats, offering more power and efficiency, which is longer lasting compared to solar and wind technologies, that also makes use of renewable sources, such as wind and/or solar, and in addition stores and uses accumulated energy when needed, is proposed.

  4. Ocean surface waves and winds over the north Indian Ocean from satellite altimeter - preliminary results of SAC-NIO joint project

    Digital Repository Service at National Institute of Oceanography (India)

    Sarkar, A.; Rajkumar, R.; Gairola, R.M.; Gohil, B.S.; Vethamony, P.; Rao, L.V.G.

    With the aim of retrieving, validating and mapping ocean surface winds and waves in the north Indian Ocean, GEOSAT altimeter data for the period November 1986 to October 1987 and available sea truth data for the above period were processed in SAC...

  5. Relationship of oceanic whitecap coverage to wind speed and wind history

    NARCIS (Netherlands)

    Callaghan, A.; Leeuw, G. de; Cohen, L.; O'Dowd, C.D.

    2008-01-01

    Sea surface images obtained during the 2006 Marine Aerosol Production (MAP) campaign in the North East Atlantic were analysed for values of percentage whitecap coverage (W). Values of W are presented for wind speeds up to circa 23 m s-1. The W data were divided into two overlapping groups and a

  6. A Statistical Approach to WindSat Ocean Surface Wind Vector Retrieval

    Science.gov (United States)

    2006-01-01

    Crane for assisting in initial development of the regression software. REFERENCES [1] P. W. Gaiser, K. St. Germain, E. M. Twarog , G. A. Poe, W. Purdy...Remote Sens., vol. 40, no. 1, pp. 79–89, Jan. 2002. [12] E. Twarog , P. W. Gaiser, B. Purdy, L. Jones, K. St. Germain, and G. Poe, “WindSat post-launch

  7. Reducing AC-Winding Losses in High-Current High-Power Inductors

    DEFF Research Database (Denmark)

    Nymand, Morten; Madawala, Udaya K.; Andersen, Michael Andreas E.

    2009-01-01

    Foil windings are preferable in high-current high-power inductors to realize compact designs and to reduce dc-current losses. At high frequency, however, proximity effect will cause very significant increase in ac resistance in multi-layer windings, and lead to high ac winding losses. This paper ...

  8. Comparison of wind data from QuikSCAT and buoys in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Satheesan, K.; Sarkar, A.; Parekh, A.; RameshKumar, M.R.; Kuroda, Y.

    stream_size 24759 stream_content_type text/plain stream_name Int_J_Remote_Sens_28_2375p.pdf.txt stream_source_info Int_J_Remote_Sens_28_2375p.pdf.txt Content-Encoding UTF-8 Content-Type text/plain; charset=UTF-8 1... help a wide variety of studies of oceanic processes and improve weather forecast via data assimilation in the operational models (Goswami and Rajagopal, 2003). The idea of remote sensing of ocean surface winds was based on the hypothesis...

  9. The influence of small-scale sea surface temperature gradients on surface vector winds and subsequent impacts on oceanic Ekman pumping

    Science.gov (United States)

    Hughes, Paul J.

    Satellite observations have revealed a small-scale (air--sea coupling in regions of strong sea surface temperature (SST) gradients (e.g., fronts, currents, eddies, and tropical instability waves), where the surface wind and wind stress are modified. Surface winds and wind stresses are persistently higher over the warm side of the SST front compared to the cool side, causing perturbations in the dynamically and thermodynamically curl and divergence fields. Capturing this small-scale SST--wind variability is important because it can significantly impact both local and remote (i.e., large scale) oceanic and atmospheric processes. The SST--wind relationship is not well represented in numerical weather prediction (NWP) and climate models, and the relative importance of the physical processes that are proposed to be responsible for this relationship is actively and vehemently debated. This study focuses on the physical mechanisms that are primarily responsible for the SST-induced changes in surface wind and wind stress, and on the physical implication on ocean forcing through Ekman pumping. The roles that SST-induced atmospheric baroclinicity and boundary-layer stability play in modifying the surface vector wind in regions of strong SST gradients are examined with an idealized model. Modeled changes in surface wind speed due to changes in atmospheric boundary-layer stability and baroclinicity are largely between -2.0 and 2.0 m s-1, which is consistent with past observational findings. The baroclinic-related changes in the surface vector wind are found to have a largely linear dependence on the SST gradient, whereas the stability-related changes are highly non-linear. The linearity of the baroclinic impacts matches that of the observed (satellite and in situ) SST--wind relationship. This result suggests that the baroclinic-related mechanism is the leading factor in driving the observed surface wind response to strong open ocean SST fronts on scales greater than 25 km

  10. Inrush Current Simulation of Two Windings Power Transformer using Machine Parameters Estimated by Design Procedure of Winding Structure

    Science.gov (United States)

    Tokunaga, Yoshitaka; Kubota, Kunihiro

    This paper presents estimation techniques of machine parameters for two windings power transformer using design procedure of winding structure. Especially, it is very difficult to obtain machine parameters for transformers in customers' facilities. Using estimation techniques, machine parameters could be calculated from the only nameplate data of these transformers. Subsequently, EMTP-ATP simulation of the inrush current was carried out using machine parameters estimated by design procedure of winding structure and simulation results were reproduced measured waveforms.

  11. Extreme wind-wave modeling and analysis in the south Atlantic ocean

    Science.gov (United States)

    Campos, R. M.; Alves, J. H. G. M.; Guedes Soares, C.; Guimaraes, L. G.; Parente, C. E.

    2018-04-01

    A set of wave hindcasts is constructed using two different types of wind calibration, followed by an additional test retuning the input source term Sin in the wave model. The goal is to improve the simulation in extreme wave events in the South Atlantic Ocean without compromising average conditions. Wind fields are based on Climate Forecast System Reanalysis (CFSR/NCEP). The first wind calibration applies a simple linear regression model, with coefficients obtained from the comparison of CFSR against buoy data. The second is a method where deficiencies of the CFSR associated with severe sea state events are remedied, whereby "defective" winds are replaced with satellite data within cyclones. A total of six wind datasets forced WAVEWATCH-III and additional three tests with modified Sin in WAVEWATCH III lead to a total of nine wave hindcasts that are evaluated against satellite and buoy data for ambient and extreme conditions. The target variable considered is the significant wave height (Hs). The increase of sea-state severity shows a progressive increase of the hindcast underestimation which could be calculated as a function of percentiles. The wind calibration using a linear regression function shows similar results to the adjustments to Sin term (increase of βmax parameter) in WAVEWATCH-III - it effectively reduces the average bias of Hs but cannot avoid the increase of errors with percentiles. The use of blended scatterometer winds within cyclones could reduce the increasing wave hindcast errors mainly above the 93rd percentile and leads to a better representation of Hs at the peak of the storms. The combination of linear regression calibration of non-cyclonic winds with scatterometer winds within the cyclones generated a wave hindcast with small errors from calm to extreme conditions. This approach led to a reduction of the percentage error of Hs from 14% to less than 8% for extreme waves, while also improving the RMSE.

  12. OGCM Simulations of Equatorial Pacific Current and Temperature to ERS-1, FSU and NMC Surface Winds and to Assimilation of Subsurface Temperature Data

    Science.gov (United States)

    Halpern, David

    1995-01-01

    The relative accuracies of three surface wind data products for the tropical Pacific Ocean during April 1992 to March 1994 were examined by analyzing temperature and current fields along the equator, which were simulated with an ocean general circulation model. Simulations were made with and without assimilation of surface and subsurface temperature data. Simulated currents were compared with observations at three sites (170oW, 140oW, 110oW) at the equator. Model-generated currents and temperatures indicated that the ERS-1 westward wind speeds were low compared to the FSU and NMC winds. With data assimilation, the agreement between simulated and observed currents was highest at 170oW and lowest at 110oW.

  13. NODC Standard Format Ocean Wind Time Series from Buoys (F101) Data (1975-1985) (NODC Accession 0014194)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This file type contains time series measurements of wind and other surface meteorological parameters taken at fixed locations. The instrument arrays may be deployed...

  14. Recent wind-driven change in Subantarctic Mode Water and its impact on ocean heat storage

    Science.gov (United States)

    Gao, Libao; Rintoul, Stephen R.; Yu, Weidong

    2018-01-01

    The subduction and export of Subantarctic Mode Water (SAMW) supplies the upper limb of the overturning circulation and makes an important contribution to global heat, freshwater, carbon and nutrient budgets1-5. Upper ocean heat content has increased since 2006, helping to explain the so-called global warming hiatus between 1998 and 2014, with much of the ocean warming concentrated in extratropical latitudes of the Southern Hemisphere in close association with SAMW and Antarctic Intermediate Water (AAIW)6,7. Here we use Argo observations to assess changes in the thickness, depth and heat content of the SAMW layer. Between 2005 and 2015, SAMW has thickened (3.6 ± 0.3 m yr-1), deepened (2.4 ± 0.2 m yr-1) and warmed (3.9 ± 0.3 W m-2). Wind forcing, rather than buoyancy forcing, is largely responsible for the observed trends in SAMW. Most (84%) of the increase in SAMW heat content is the result of changes in thickness; warming by buoyancy forcing (increased heat flux to the ocean) accounts for the remaining 16%. Projected increases in wind stress curl would drive further deepening of SAMW and increase in heat storage in the Southern Hemisphere oceans.

  15. Intraseasonal Variability of the Equatorial Indian Ocean Observed from Sea Surface Height, Wind, and Temperature Data

    Science.gov (United States)

    Fu, Lee-Lueng

    2007-01-01

    The forcing of the equatorial Indian Ocean by the highly periodic monsoon wind cycle creates many interesting intraseasonal variabilities. The frequency spectrum of the wind stress observations from the European Remote Sensing Satellite scatterometers reveals peaks at the seasonal cycle and its higher harmonics at 180, 120, 90, and 75 days. The observations of sea surface height (SSH) from the Jason and Ocean Topography Experiment (TOPEX)/Poseidon radar altimeters are analyzed to study the ocean's response. The focus of the study is on the intraseasonal periods shorter than the annual period. The semiannual SSH variability is characterized by a basin mode involving Rossby waves and Kelvin waves traveling back and forth in the equatorial Indian Ocean between 10(deg)S and 10(deg)N. However, the interference of these waves with each other masks the appearance of individual Kelvin and Rossby waves, leading to a nodal point (amphidrome) of phase propagation on the equator at the center of the basin. The characteristics of the mode correspond to a resonance of the basin according to theoretical models. The theory also calls for similar modes at 90 and 60 days.

  16. Intraseasonal variability of upper-ocean currents and photosynthetic primary production along the U.S. west coast associated with the Madden-Julian Oscillation

    Science.gov (United States)

    Barrett, B.; Davies, A. R.; Steppe, C. N.; Hackbarth, C.

    2017-12-01

    In the first part of this study, time-lagged composites of upper-ocean currents from February to May of 1993-2016 were binned by active phase of the leading atmospheric mode of intraseasonal variability, the Madden-Julian Oscillation (MJO). Seven days after the convectively active phase of the MJO enters the tropical Indian Ocean, anomalously strong south-southeastward upper-ocean currents are observed along the majority of U.S. west coast. Seven days after the convectively active phase enters the tropical western Pacific Ocean, upper-ocean current anomalies reverse along the U.S. west coast, with weaker southward flow. A physical pathway to the ocean was found for both of these: (a) tropical MJO convection modulates upper-tropospheric heights and circulation over the Pacific Ocean; (b) those anomalous atmospheric heights adjust the strength and position of the Aleutian Low and Hawaiian High; (c) surface winds change in response to the adjusted atmospheric pressure patterns; and (d) those surface winds project onto upper-ocean currents. In the second part of this study, we investigated if the MJO modulated intraseasonal variability of surface wind forcing and upper-ocean currents projected onto phytoplankton abundance along the U.S. west coast. Following a similar methodology, time-lagged, level 3 chlorophyll-a satellite products (a proxy for photosynthetic primary production) were binned by active MJO phase and analyzed for statistical significance using the Student's t test. Results suggest that intraseasonal variability of biological production along the U.S. west coast may be linked to the MJO, particularly since the time scale of the life cycle of phytoplankton is similar to the time scale of the MJO.

  17. The Current State of Additive Manufacturing in Wind Energy Systems

    Energy Technology Data Exchange (ETDEWEB)

    Mann, Margaret [National Renewable Energy Lab. (NREL), Golden, CO (United States); Palmer, Sierra [Worcester Polytechnic Institute (WPI), , Worcester, MA (United States); Lee, Dominic [National Renewable Energy Lab. (NREL), Golden, CO (United States); Kurup, Parthiv [National Renewable Energy Lab. (NREL), Golden, CO (United States); Remo, Timothy [National Renewable Energy Lab. (NREL), Golden, CO (United States); Jenne, Dale Scott [National Renewable Energy Lab. (NREL), Golden, CO (United States); Richardson, Bradley S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Love, Lonnie J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Post, Brian K. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-12-01

    Wind power is an inexhaustible form of energy that is being captured throughout the U.S. to power the engine of our economy. A robust, domestic wind industry promises to increase U.S. industry growth and competitiveness, strengthen U.S. energy security independence, and promote domestic manufacturing nationwide. As of 2016, ~82GW of wind capacity had been installed, and wind power now provides more than 5.5% of the nation’s electricity and supports more than 100,000 domestic jobs, including 500 manufacturing facilities in 43 States. To reach the U.S. Department of Energy’s (DOE’s) 2015 Wind Vision study scenario of wind power serving 35% of the nation's end-use demand by 2050, significant advances are necessary in all areas of wind technologies and market. An area that can greatly impact the cost and rate of innovation in wind technologies is the use of advanced manufacturing, with one of the most promising areas being additive manufacturing (AM). Considering the tremendous promise offered by advanced manufacturing, it is the purpose of this report to identify the use of AM in the production and operation of wind energy systems. The report has been produced as a collaborative effort for the DOE Wind Energy Technology Office (WETO), between Oak Ridge National Laboratory (ORNL) and the National Renewable Energy Laboratory (NREL).

  18. High-latitude Conic Current Sheets in the Solar Wind

    Energy Technology Data Exchange (ETDEWEB)

    Khabarova, Olga V.; Obridko, Vladimir N.; Kharshiladze, Alexander F. [Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation of the Russian Academy of Sciences (IZMIRAN), Moscow (Russian Federation); Malova, Helmi V. [Scobeltsyn Nuclear Physics Institute of Lomonosov Moscow State University, Moscow (Russian Federation); Kislov, Roman A.; Zelenyi, Lev M. [Space Research Centre of the Polish Academy of Sciences (CBK PAN), Warsaw (Poland); Tokumaru, Munetoshi; Fujiki, Ken’ichi [Institute for Space-Earth Environmental Research, Nagoya University (Japan); Sokół, Justyna M.; Grzedzielski, Stan [Space Research Centre of the Polish Academy of Sciences (CBK), Warsaw (Poland)

    2017-02-10

    We provide observational evidence for the existence of large-scale cylindrical (or conic-like) current sheets (CCSs) at high heliolatitudes. Long-lived CCSs were detected by Ulysses during its passages over the South Solar Pole in 1994 and 2007. The characteristic scale of these tornado-like structures is several times less than a typical width of coronal holes within which the CCSs are observed. CCS crossings are characterized by a dramatic decrease in the solar wind speed and plasma beta typical for predicted profiles of CCSs. Ulysses crossed the same CCS at different heliolatitudes at 2–3 au several times in 1994, as the CCS was declined from the rotation axis and corotated with the Sun. In 2007, a CCS was detected directly over the South Pole, and its structure was strongly highlighted by the interaction with comet McNaught. Restorations of solar coronal magnetic field lines reveal the occurrence of conic-like magnetic separators over the solar poles in both 1994 and 2007. Such separators exist only during solar minima. Interplanetary scintillation data analysis confirms the presence of long-lived low-speed regions surrounded by the typical polar high-speed solar wind in solar minima. Energetic particle flux enhancements up to several MeV/ nuc are observed at edges of the CCSs. We built simple MHD models of a CCS to illustrate its key features. The CCSs may be formed as a result of nonaxiality of the solar rotation axis and magnetic axis, as predicted by the Fisk–Parker hybrid heliospheric magnetic field model in the modification of Burger and coworkers.

  19. Uncertainty in the global oceanic CO2 uptake induced by wind forcing: quantification and spatial analysis

    Directory of Open Access Journals (Sweden)

    A. Roobaert

    2018-03-01

    Full Text Available The calculation of the air–water CO2 exchange (FCO2 in the ocean not only depends on the gradient in CO2 partial pressure at the air–water interface but also on the parameterization of the gas exchange transfer velocity (k and the choice of wind product. Here, we present regional and global-scale quantifications of the uncertainty in FCO2 induced by several widely used k formulations and four wind speed data products (CCMP, ERA, NCEP1 and NCEP2. The analysis is performed at a 1°  ×  1° resolution using the sea surface pCO2 climatology generated by Landschützer et al. (2015a for the 1991–2011 period, while the regional assessment relies on the segmentation proposed by the Regional Carbon Cycle Assessment and Processes (RECCAP project. First, we use k formulations derived from the global 14C inventory relying on a quadratic relationship between k and wind speed (k = c ⋅ U102; Sweeney et al., 2007; Takahashi et al., 2009; Wanninkhof, 2014, where c is a calibration coefficient and U10 is the wind speed measured 10 m above the surface. Our results show that the range of global FCO2, calculated with these k relationships, diverge by 12 % when using CCMP, ERA or NCEP1. Due to differences in the regional wind patterns, regional discrepancies in FCO2 are more pronounced than global. These global and regional differences significantly increase when using NCEP2 or other k formulations which include earlier relationships (i.e., Wanninkhof, 1992; Wanninkhof et al., 2009 as well as numerous local and regional parameterizations derived experimentally. To minimize uncertainties associated with the choice of wind product, it is possible to recalculate the coefficient c globally (hereafter called c∗ for a given wind product and its spatio-temporal resolution, in order to match the last evaluation of the global k value. We thus performed these recalculations for each wind product at the resolution and time period of our study

  20. The effects of wind and rainfall on suspended sediment concentration related to the 2004 Indian Ocean tsunami

    International Nuclear Information System (INIS)

    Zhang Xinfeng; Tang Danling; Li Zizhen; Zhang Fengpan

    2009-01-01

    The effects of rainfall and wind speed on the dynamics of suspended sediment concentration (SSC), during the 2004 Indian Ocean tsunami, were analyzed using spatial statistical models. The results showed a positive effect of wind speed on SSC, and inconsistent effects (positive and negative) of rainfall on SSC. The effects of wind speed and rainfall on SSC weakened immediately around the tsunami, indicating tsunami-caused floods and earthquake-induced shaking may have suddenly disturbed the ocean-atmosphere interaction processes, and thus weakened the effects of wind speed and rainfall on SSC. Wind speed and rainfall increased markedly, and reached their maximum values immediately after the tsunami week. Rainfall at this particular week exceeded twice the average for the same period over the previous 4 years. The tsunami-affected air-sea interactions may have increased both wind speed and rainfall immediately after the tsunami week, which directly lead to the variations in SSC.

  1. Fault current contribution from VSC-based wind turbines to the grid

    DEFF Research Database (Denmark)

    Valentini, Massimo; Akhmatov, Vladislav; Iov, Florin

    2008-01-01

    current injections during the fault. In this paper an equivalent VSC-based wind turbine model for short-circuit calculations at steady-state conditions is developed and presented. The model is implemented in DigSILENT PowerFactory using the DPL-Programming Language. The developed wind turbine model...... Power. The wind turbine model is finally rescaled to obtain an aggregate wind farm model and used to perform short-circuit calculations in a realistic scenario; the Danish transmission system is considered and a large offshore wind farm with VSC-based wind turbines is included in the investigation....

  2. Comparisons of Monthly Mean 10 M Wind Speeds from Satellites and NWP Products Over the Global Ocean

    Science.gov (United States)

    2009-10-09

    winds. Negative difference values in the color palette are shown in red. (c) Number of wind measurements used for forming monthly mean winds in...I-buoy, NOGAPS-buoy, etc.). The color palette does not convey these large differences, but in fact differences for sensible heat fluxes are >100 W...reflection for the along track scanning radio- meter, / Atmos. Oceanic Technoi, 13, 126-141. Weissman, D. E., W. J. Plant , W. C. Keller, and V. G

  3. Wind effect on currents in a thin surface layer of coastal waters faced open-sea

    International Nuclear Information System (INIS)

    Nakano, Masanao; Isozaki, Hisaaki; Isozaki, Tokuju; Nemoto, Masashi; Hasunuma, Keiichi; Kitamura, Takashi

    2009-01-01

    Two-years of continuous observation of wind and current were carried out to investigate the relationship between them in the coastal waters off Tokai-mura, Ibaraki prefecture. Three instruments to measure the current were set in a thin surface layer of 3 m above the strong pycnocline, which is a common feature in coastal waters. Both of the power spectra of wind and currents showed very similar features, an outstanding high peak at 24-hour period and a range of high peaks longer than several-days period. The long term variation of the wind field always contained north-wind component, which contributed to forming the southward current along the shore throughout the year. A high correlation coefficient (0.64) was obtained between the wind and the current at a depth of 0.5 m on the basis of the two-year observation. Harmonic analysis revealed that an outstanding current with 24-hour period was the S 1 component (meteorological tide), and was driven by land and sea breezes. These breezes also contained solar tidal components such as K 1 , P 1 and S 2 . These wind components added their own wind driven currents on the original tidal currents. This meant that land and sea breezes generated wind driven currents with solar tidal periods which behaved like astronomical tidal currents. As result, coastal currents contained pseudo tidal currents which behaved like astronomical tidal currents. (author)

  4. Short-Circuit Current Analysis for DFIG Wind Farm Considering the Action of a Crowbar

    OpenAIRE

    Yan Hong Yuan; Feng Wu

    2018-01-01

    With the increasing capacity of wind farms integrated into the power grid, the short-circuit current analysis for wind farms becomes more and more important. Since the wind turbine is usually integrated into the power grid via power electronic devices, the “crowbar” is installed in the wind turbine to protect the power electronic devices and to improve the fault ride through capability. The impact of the crowbar has to be considered during the short-circuit current analysis for the wind farm....

  5. NODC Standard Format Coastal Ocean Wave and Current (F181) Data from the Atlantic Remote Sensing Land/Ocean Experiment (ARSLOE) (1980) (NODC Accession 0014202)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains time series coastal ocean wave and current data collected during the Atlantic Remote Sensing Land/Ocean Experiment (ARSLOE). ARSLOE was...

  6. Assessment of Energy Production Potential from Ocean Currents along the United States Coastline

    Energy Technology Data Exchange (ETDEWEB)

    Haas, Kevin A. [Georgia Inst. of Technology, Atlanta, GA (United States)

    2013-10-03

    Increasing energy consumption and depleting reserves of fossil fuels have resulted in growing interest in alternative renewable energy from the ocean. Ocean currents are an alternative source of clean energy due to their inherent reliability, persistence and sustainability. General ocean circulations exist in the form of large rotating ocean gyres, and feature extremely rapid current flow in the western boundaries due to the Coriolis Effect. The Gulf Stream system is formed by the western boundary current of the North Atlantic Ocean that flows along the east coastline of the United States, and therefore is of particular interest as a potential energy resource for the United States.

  7. Correlated Increase of High Ocean Waves and Winds in the Ice-Free Waters of the Arctic Ocean.

    Science.gov (United States)

    Waseda, Takuji; Webb, Adrean; Sato, Kazutoshi; Inoue, Jun; Kohout, Alison; Penrose, Bill; Penrose, Scott

    2018-03-14

    The long-term trend of extreme ocean waves in the emerging ice-free waters of the summer Arctic is studied using ERA-Interim wave reanalysis, with validation by two drifting wave buoys deployed in summer 2016. The 38-year-long reanalysis dataset reveals an increase in the expected largest significant wave height from 2.3 m to 3.1 m in the ice-free water from the Laptev to the Beaufort Seas during October. The trend is highly correlated with the expected increase in highest wind speed from 12.0 m/s to 14.2 m/s over the ice-free ocean, and less so with the extent of the ice-free water. Since the storms in this area did not strengthen throughout the analysis period, the increase in the expected largest significant wave height follows from the enhanced probability of storms in ice-free waters, which is pertinent to the estimation of extreme sea conditions along the Northern Sea Route.

  8. Influence of El Niño Wind Stress Anomalies on South Brazil Bight Ocean Volume Transports

    Directory of Open Access Journals (Sweden)

    Luiz Paulo de Freitas Assad

    2015-01-01

    Full Text Available The knowledge of wind stress variability could represent an important contribution to understand the variability over upper layer ocean volume transports. The South Brazilian Bight (SBB circulation had been studied by numerous researchers who predominantly attempted to estimate its meridional volume transport. The main objective and contribution of this study is to identify and quantify possible interannual variability in the ocean volume transport in the SBB induced by the sea surface wind stress field. A low resolution ocean global circulation model was implemented to investigate the volume transport variability. The results obtained indicate the occurrence of interannual variability in meridional ocean volume transports along three different zonal sections. These results also indicate the influence of a wind driven large-scale atmospheric process that alters locally the SBB and near-offshore region wind stress field and consequently causes interannual variability in the upper layer ocean volume transports. A strengthening of the southward flow in 25°S and 30°S was observed. The deep layer ocean volume transport in the three monitored sections indicates a potential dominance of other remote ocean processes. A small time lag between the integrated meridional volume transports changes in each monitored zonal section was observed.

  9. Validation of HF Radar ocean surface currents in the Ibiza Channel using lagrangian drifters, moored current meter and underwater gliders

    Science.gov (United States)

    Lana, Arancha; Fernández, Vicente; Orfila, Alejandro; Troupin, Charles; Tintoré, Joaquín

    2015-04-01

    SOCIB High Frequency (HF) radar is one component of a multi-platform system located in the Balearic Islands and made up of Lagrangian platforms (profilers and drifting buoys), fixed stations (sea-level, weather, mooring and coastal), beach monitoring (camera), gliders, a research vessel as well as an ocean forecast system (waves and hydrodynamics). The HF radar system overlooks the Ibiza Channel, known as a 'choke point" where Atlantic and Mediterranean water masses interact and where meridional exchanges of water mass properties between the Balearic and the Algerian sub-basins take place. In order to determine the reliability of surface velocity measurements in this area, a quality assessment of the HF Radar is essential. We present the results of several validation experiments performed in the Ibiza Channel in 2013 and 2014. Of particular interest is an experiment started in September 2014 when a set of 13 surface drifters with different shapes and drogue lengths were released in the area covered by the HF radar. The drifter trajectories can be examined following the SOCIB Deployment Application (DAPP): http://apps.socib.es/dapp. Additionally, a 1-year long time series of surface currents obtained from a moored surface current-meter located in the Ibiza Channel, inside the area covered by the HF radar, was also used as a useful complementary validation exercise. Direct comparison between both radial surface currents from each radar station and total derived velocities against drifters and moored current meter velocities provides an assessment of the HF radar data quality at different temporal periods and geographical areas. Statistics from these comparisons give good correlation and low root-mean-square deviation. The results will be discussed for different months, geographical areas and types of surface drifters and wind exposure. Moreover, autonomous underwater glider constitutes an additional source of information for the validation of the observed velocity

  10. Western Gulf of Mexico, June 1993 to June 1994 Average Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_wgom_AVG_MMS_1994

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the western...

  11. Eastern Gulf of Mexico, February 1996 to June 1997 Average Ocean Currents, Geographic NAD83, MMS (1999) [ocean_currents_egom_AVG_MMS_1997

    Data.gov (United States)

    Louisiana Geographic Information Center — This is one data set of a data package consisting of thirteen point data sets that have as attributes the direction and velocity of ocean currents in the 'eastern'...

  12. Numerical simulation of wave-current interaction under strong wind conditions

    Science.gov (United States)

    Larrañaga, Marco; Osuna, Pedro; Ocampo-Torres, Francisco Javier

    2017-04-01

    Although ocean surface waves are known to play an important role in the momentum and other scalar transfer between the atmosphere and the ocean, most operational numerical models do not explicitly include the terms of wave-current interaction. In this work, a numerical analysis about the relative importance of the processes associated with the wave-current interaction under strong off-shore wind conditions in Gulf of Tehuantepec (the southern Mexican Pacific) was carried out. The numerical system includes the spectral wave model WAM and the 3D hydrodynamic model POLCOMS, with the vertical turbulent mixing parametrized by the kappa-epsilon closure model. The coupling methodology is based on the vortex-force formalism. The hydrodynamic model was forced at the open boundaries using the HYCOM database and the wave model was forced at the open boundaries by remote waves from the southern Pacific. The atmospheric forcing for both models was provided by a local implementation of the WRF model, forced at the open boundaries using the CFSR database. The preliminary analysis of the model results indicates an effect of currents on the propagation of the swell throughout the study area. The Stokes-Coriolis term have an impact on the transient Ekman transport by modifying the Ekman spiral, while the Stokes drift has an effect on the momentum advection and the production of TKE, where the later induces a deepening of the mixing layer. This study is carried out in the framework of the project CONACYT CB-2015-01 255377 and RugDiSMar Project (CONACYT 155793).

  13. Remote sensing of ocean currents. [Loop Current in Gulf of Mexico

    Science.gov (United States)

    Maul, G. A. (Principal Investigator)

    1974-01-01

    The author has identified the following significant results. A time series of the Loop Current in the Gulf of Mexico, covering an annual cycle of growth, spreading, and decay, has been obtained in synchronization with ERTS-1. Computer enhanced images, which are necessary to extract useful oceanic information, show that the current can be observed either by color or sea state effects associated with the cyclonic boundary. The color effect relates to the spectral variations in the optical properties of the water and its suspended particles, and is studied by radiative transfer theory. Significant oceanic parameters identified are: the probability of forward scattering, and the ratio of scattering to total attenuation. Several spectra of upwelling diffuse light are computed as a function of the concentration of particles and yellow substance. These calculations compare favorably with experimental measurements and show that the ratio of channels method gives ambiguous interpretative results. These results are used to discuss features in images where surface measurements were obtained and are extended to tentative explanation in others.

  14. Remote sensing of ocean current boundary layer. [Loop Current in Gulf of Mexico

    Science.gov (United States)

    Maul, G. A. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. A time series of the Loop Current in the Gulf of Mexico, covering an annual cycle of growth, spreading, and decay, has been obtained in synchronization with ERTS-1. Computer enhanced images, which are necessary to extract useful oceanic information, show that the current can be observed either by color or sea state effects associated with the cyclonic boundary. The color effect relates to the spectral variations in the optical properties of the water and its suspended particles, and is studied by radiative transfer theory. Significant oceanic parameters identified are: the probability of forward scattering, and the ratio of scattering to total attenuation. Several spectra of upwelling diffuse light are computed as a function of the concentration of particles and yellow substance. These calculations compare favorably with experimental measurements and show that the ratio of channels method gives ambiguous interpretative results. These results are used to discuss features in images where surface measurements were obtained and are extended to tentative explanation in others.

  15. Current R and D needs in wind energy technology

    International Nuclear Information System (INIS)

    Maribo Pedersen, B.

    1995-01-01

    The meeting, hosted by NOVEM, the Netherlands Agency for Energy and the Environment, was attended by 22 people. The purpose of the meeting was to get an impression of how far the efforts spent until now on worldwide research and development have brought the general understanding of, and possibly solutions to, the various problems within wind energy technology - thereby providing some guidance as to where to go from now. In 1994 it was estimated that more than 100 million U.S. dollars was spent on R, D and D by those OECD countries which have a wind energy program, and that since 1974 at least 1000 mil. U.S. dollars must have been spent. The necessity of continued basic research within certain areas was recognized, and it was emphasized that the size of the research teams should always be greater than 'the critical mass'. There seemed to be consensus among all participants that the areas for continued research were the following: aerodynamics, aeroelasticity and load calculations, aeroacoustics (verification of fatigue calculation procedures for 3D stress distribution, establishing a data base of material properties), lightning protection measures, offshore installations (combined wind/wave loading, dynamics of support structures, wind and turbulence over the open sea), power conversion and wind turbine - grid interaction. (EG)

  16. Satellite Remote Sensing in Offshore Wind Energy

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay; Badger, Merete; Astrup, Poul

    2013-01-01

    Satellite remote sensing of ocean surface winds are presented with focus on wind energy applications. The history on operational and research-based satellite ocean wind mapping is briefly described for passive microwave, scatterometer and synthetic aperture radar (SAR). Currently 6 GW installed...

  17. Application of Monochromatic Ocean Wave Forecasts to Prediction of Wave-Induced Currents

    Science.gov (United States)

    Poole, L. R.

    1975-01-01

    Stoke's wave-induced currents are compared, for variety of wind conditions resulting in partially developed seas and for two water depths, with currents induced by average and significant monochromatic waves related to Bretschneider spectrum.

  18. Low-frequency variability of Western Boundary Currents in the turbulent ocean: intrinsic modes and atmospheric forcing

    Science.gov (United States)

    Sérazin, Guillaume; Penduff, Thierry; Terray, Laurent; Grégorio, Sandy; Barnier, Bernard; Molines, Jean-Marc

    2015-04-01

    Ocean-atmosphere heat fluxes are particularly strong in Western Boundary Current (WBC) regions where SST front variations influence basin-scale climate variability. Observed low-frequency fluctuations in latitude and strength of these oceanic jets are classically thought to be essentially atmospherically-driven by wind stress curl variability via the oceanic Rossby wave adjustment. Yet academic eddy-resolving process-oriented models with double-gyre configurations have revealed that an idealized WBC may exhibit low-frequency intrinsic fluctuations without low-frequency external forcing (e.g. Berloff et al., 2007, Dijkstra and Ghil, 2005, etc). Experiments with eddying Ocean General Circulation Models (OGCMs) have also shown that the amount of low-frequency Sea Level Anomaly (SLA) variability is largely intrinsic in WBCs (Penduff et al. 2011; Sérazin et al 2014) and that the frontal-scale (performed on zonally-averaged SLA fields of four main WBCs (e.g. Gulf Stream, Kuroshio Extension, Agulhas Current and East Australian Current). The first two modes of the KE and GS exhibit a similar spatial structure that is shaped by oceanic intrinsic processes. The frequency content is however different between the intrinsic and total Principal Components, the former containing a wide range of timescales similar to a red noise and the latter being more autocorrelated at interannual-to-decadal timescales. These modes are compared with those obtained from the 20 years of altimetry observation and relationships with low-frequency westward propagative features in the respective oceanic basin are investigated. We argue that OGCM studies of intrinsic dynamic of WBCs are key to interpreting their observed total variability, which might result from a subtle mixing between a non-linear small-scale response of intrinsic modes to the atmospheric forcing and a direct basin-scale linear response to the atmosphere.

  19. Wind Plant Preconstruction Energy Estimates. Current Practice and Opportunities

    Energy Technology Data Exchange (ETDEWEB)

    Clifton, Andrew [National Renewable Energy Lab. (NREL), Golden, CO (United States); Smith, Aaron [National Renewable Energy Lab. (NREL), Golden, CO (United States); Fields, Michael [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2016-04-19

    Understanding the amount of energy that will be harvested by a wind power plant each year and the variability of that energy is essential to assessing and potentially improving the financial viability of that power plant. The preconstruction energy estimate process predicts the amount of energy--with uncertainty estimates--that a wind power plant will deliver to the point of revenue. This report describes the preconstruction energy estimate process from a technical perspective and seeks to provide insight into the financial implications associated with each step.

  20. Currents connecting communities: nearshore community similarity and ocean circulation.

    Science.gov (United States)

    Watson, J R; Hays, C G; Raimondi, P T; Mitarai, S; Dong, C; McWilliams, J C; Blanchette, C A; Caselle, J E; Siegel, D A

    2011-06-01

    Understanding the mechanisms that create spatial heterogeneity in species distributions is fundamental to ecology. For nearshore marine systems, most species have a pelagic larval stage where dispersal is strongly influenced by patterns of ocean circulation. Concomitantly, nearshore habitats and the local environment are also influenced by ocean circulation. Because of the shared dependence on the seascape, distinguishing the relative importance of the local environment from regional patterns of dispersal for community structure remains a challenge. Here, we quantify the "oceanographic distance" and "oceanographic asymmetry" between nearshore sites using ocean circulation modeling results. These novel metrics quantify spatial separation based on realistic patterns of ocean circulation, and we explore their explanatory power for intertidal and subtidal community similarity in the Southern California Bight. We find that these metrics show significant correspondence with patterns of community similarity and that their combined explanatory power exceeds that of the thermal structure of the domain. Our approach identifies the unique influence of ocean circulation on community structure and provides evidence for oceanographically mediated dispersal limitation in nearshore marine communities.

  1. An Anisotropic Ocean Surface Emissivity Model Based on WindSat Polarimetric Brightness Observations

    Science.gov (United States)

    Smith, D. F.; Gasiewski, A. J.; Sandeep, S.; Weber, B. L.

    2012-12-01

    The goal of this research has been to develop a standardized fast full-Stokes ocean surface emissivity model with Jacobian for a wind-driven ocean surface applicable at arbitrary microwave frequencies, polarizations, and incidence angles. The model is based on the Ohio State University (OSU) two-scale code for surface emission developed by Johnson (2006, IEEE TGRS, 44, 560) but modified as follows: (1) the Meissner-Wentz dielectric permittivity (2012, IEEE TGRS, 50, 3004) replaces the original permittivity, (2) the Elfouhaily sea surface spectrum (1997, JGR, 102, C7,15781) replaces the Durden-Vesecky spectrum (1985, IEEE TGRS, OE-10, 445), but the Durden-Vesecky angular spreading function is retained, (3) the high-frequency portion of the Elfouhaily spectrum is multiplied by the Pierson-Moskowitz shape spectrum to correct an error in the original paper, (4) the generalized Phillips-Kitaigorodskii equilibrium range parameter for short waves is modeled as a continuous function of the friction velocity at the water surface to eliminate a discontinuous jump in the original paper. A total of five physical tuning parameters were identified, including the spectral strength and the hydrodynamic modulation factor. The short wave part of the spectrum is also allowed to have an arbitrary ratio relative to the long wave part. The foam fraction is multiplied by a variable correction factor, and also modulated to allow an anisotropic foam fraction with more foam on the leeward side of a wave. The model is being tuned against multi-year sequences of WindSat and Special Sensor Microwave/Imager (SSMI) data as analyzed by Meissner and Wentz (2012, IEEE TGRS, 50, 3004) for up to four Stokes brightnesses and in all angular harmonics up to two in twenty five wind bins from 0.5-25.5 m/s and of 1 m/s width. As a result there are 40 brightnesses per wind bin, for a total of 1000 brightnesses used to constrain the modified model. A chi-squared tuning criterion based on error standard

  2. Multi-phase alternative current machine winding design | Khan ...

    African Journals Online (AJOL)

    ... single-phase to 18-phase excitation. Experimental results of a five-phase induction machine supplied from a static five-phase supply are provided to support the proposed design. Keywords: AC machine, Multi-phase machine, Stator winding, Five-phase. International Journal of Engineering, Science and Technology, Vol.

  3. Wind Turbine Failures - Tackling current Problems in Failure Data Analysis

    Science.gov (United States)

    Reder, M. D.; Gonzalez, E.; Melero, J. J.

    2016-09-01

    The wind industry has been growing significantly over the past decades, resulting in a remarkable increase in installed wind power capacity. Turbine technologies are rapidly evolving in terms of complexity and size, and there is an urgent need for cost effective operation and maintenance (O&M) strategies. Especially unplanned downtime represents one of the main cost drivers of a modern wind farm. Here, reliability and failure prediction models can enable operators to apply preventive O&M strategies rather than corrective actions. In order to develop these models, the failure rates and downtimes of wind turbine (WT) components have to be understood profoundly. This paper is focused on tackling three of the main issues related to WT failure analyses. These are, the non-uniform data treatment, the scarcity of available failure analyses, and the lack of investigation on alternative data sources. For this, a modernised form of an existing WT taxonomy is introduced. Additionally, an extensive analysis of historical failure and downtime data of more than 4300 turbines is presented. Finally, the possibilities to encounter the lack of available failure data by complementing historical databases with Supervisory Control and Data Acquisition (SCADA) alarms are evaluated.

  4. The current status of wind energy in Turkey and in the world

    Energy Technology Data Exchange (ETDEWEB)

    Ilkilic, Cumali [Department of Automotive, Faculty of Technical Education, Firat University, Elazig 23119 (Turkey); Aydin, Hueseyin; Behcet, Rasim [Department of Automotive, Faculty of Technical Education, Batman University, Batman 72060 (Turkey)

    2011-02-15

    The rapid increase in world energy demand, the depletion of conventional energy sources and the pollution caused by conventional fuels have increased the importance of developing new and renewable energy sources. Additionally, technological developments have resulted in increased energy demand for the entire world, including Turkey, especially for electrical energy. At present, wind energy is receiving considerable attention. This report focuses on the current status of wind energy in Turkey and in the world. An overview of wind energy in Turkey is presented, and its current status, application, support mechanisms and associated legislation in Turkey are described. Wind energy and its status in the world are also addressed. It can be concluded from this analysis that wind energy utilization in Turkey and throughout world has sharply increased. Turkey has an abundance of wind energy sources. (author)

  5. Contactless system of excitation current measurement in the windings with high inductance

    Science.gov (United States)

    Chubraeva, L.; Evseev, E.; Timofeev, S.

    2018-02-01

    The results of development, manufacturing and testing of a special contactless maintenance-free excitation current measurement system intended for the windings with high inductance, typical for superconductive alternators, are presented. The system was assembled on the brushless exciter is intended for 1 MVA wind-power generator with the winding, manufactured of high-temperature superconductors (HTSC). The alternator with brushless exciter were manufactured and successfully tested.

  6. Analysis of a Permanent Magnet Eddy Current Heater Driven by a Wind Turbine

    OpenAIRE

    TUDORACHE, T.; MELCESCU, L.; PREDESCU, M.

    2015-01-01

    This paper deals with the numerical analysis and optimal design of a Permanent Magnet Eddy Current Heater (PMECH) driven by a wind turbine. This study includes a preliminary sizing of the wind turbine, an optimal design of the PMECH from cost reduction point of view, a heat transfer analysis of the device and a study of the dynamic response of the wind system. The electromagnetic and heat transfer analysis is based on Finite Element Method (FEM) implemented in the Flux sof...

  7. NODC Standard Product: Ocean current drifter data (2 disc set) (NODC Accession 0098060)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These CD-ROMs hold over 4 million surface current observations, almost all obtained by the ship drift method. Date, data source, position, and current direction and...

  8. Ocean currents shape the microbiome of Arctic marine sediments

    NARCIS (Netherlands)

    Hamdan, L.J.; Coffin, R.B.; Sikaroodi, M.; Greinert, J.; Treude, T.; Gillevet, P.M.

    2013-01-01

    Prokaryote communities were investigated on the seasonally stratified Alaska Beaufort Shelf (ABS). Water and sediment directly underlying water with origin in the Arctic, Pacific or Atlantic oceans were analyzed by pyrosequencing and length heterogeneity-PCR in conjunction with physicochemical and

  9. A current controlled matrix converter for wind energy conversion systems based on permanent magnet synchronous generator

    OpenAIRE

    Naggar H. Saad; Ahmed A. El-Sattar; Mohamed I. Marei

    2016-01-01

    The main challenges of wind energy conversion systems (WECS) are to maximize the energy capture from the wind and injecting reactive power during the fault. This paper presents a current controlled matrix converter to interface Permanent Magnet Synchronous Generators (PMSG) based WECS with the grid. To achieve fast dynamic response with reduced current ripples, a hysteresis current control is utilized. The proposed control system decouples the active and reactive components of the PMSG curren...

  10. Microbiology of Wind-eroded Sediments: Current Knowledge and Future Research Directions

    Science.gov (United States)

    Wind erosion is a threat to the sustainability and productivity of soils that takes place at local, regional, and global scales. Current estimates of cost of wind erosion have not included the costs associated with the loss of soil biodiversity and reduced ecosystem functions. Microorganisms carrie...

  11. Analysis of a Permanent Magnet Eddy Current Heater Driven by a Wind Turbine

    Directory of Open Access Journals (Sweden)

    TUDORACHE, T.

    2015-08-01

    Full Text Available This paper deals with the numerical analysis and optimal design of a Permanent Magnet Eddy Current Heater (PMECH driven by a wind turbine. This study includes a preliminary sizing of the wind turbine, an optimal design of the PMECH from cost reduction point of view, a heat transfer analysis of the device and a study of the dynamic response of the wind system. The electromagnetic and heat transfer analysis is based on Finite Element Method (FEM implemented in the Flux software package and the dynamic response of the wind system is analyzed using a dedicated model developed under Matlab/Simulink environment.

  12. Variable speed wind turbine generator system with current controlled voltage source inverter

    International Nuclear Information System (INIS)

    Muyeen, S.M.; Al-Durra, Ahmed; Tamura, J.

    2011-01-01

    highlights: → Current controlled voltage source inverter scheme for wind power application. → Low voltage ride through of wind farm. → Variable speed wind turbine driven permanent magnet synchronous generator-operation and control. -- Abstract: The present popular trend of wind power generation is to use variable speed wind turbine (VSWT) driving a doubly fed induction generator (DFIG), wound field synchronous generator (WFSG) or permanent magnet synchronous generator (PMSG). Among them, stability analyses of DFIG type of VSWT have already been reported in many literatures. However, transient stability and low voltage ride through (LVRT) characteristics analyses for synchronous generator type of VSWT is not sufficient enough. This paper focuses on detailed LVRT characteristic analysis of variable speed wind turbine driving a PMSG (VSWT-PMSG) with current controlled voltage source inverter (CC-VSI). Modeling and suitable control strategies for overall system are developed to augment the low voltage ride through capability of variable speed wind generator, considering recent wind farm grid code. Both symmetrical and unsymmetrical faults are analyzed as network disturbances in this paper. The permanent fault due to unsuccessful reclosing of circuit breakers is taken into consideration, which is a salient feature of this study. Moreover, the dynamic characteristic is analyzed using real wind speed data measured in Hokkaido Island, Japan. The proposed control scheme is simulated by using the standard power system simulation package PSCAD/EMTDC and results are verified by comparing that of voltage controlled voltage source inverter scheme available in power system literature.

  13. Variable speed wind turbine generator system with current controlled voltage source inverter

    Energy Technology Data Exchange (ETDEWEB)

    Muyeen, S.M., E-mail: muyeen0809@yahoo.co [Dept. of Electrical Engineering, Petroleum Institute, P.O. Box 2533, Abu Dhabi (United Arab Emirates); Al-Durra, Ahmed [Dept. of Electrical Engineering, The Petroleum Institute, P.O. Box 2533, Abu Dhabi (United Arab Emirates); Tamura, J. [Dept. of EEE, Kitami Institute of Technology, 165 Koen-cho, Kitami 090-8507 (Japan)

    2011-07-15

    highlights: {yields} Current controlled voltage source inverter scheme for wind power application. {yields} Low voltage ride through of wind farm. {yields} Variable speed wind turbine driven permanent magnet synchronous generator-operation and control. -- Abstract: The present popular trend of wind power generation is to use variable speed wind turbine (VSWT) driving a doubly fed induction generator (DFIG), wound field synchronous generator (WFSG) or permanent magnet synchronous generator (PMSG). Among them, stability analyses of DFIG type of VSWT have already been reported in many literatures. However, transient stability and low voltage ride through (LVRT) characteristics analyses for synchronous generator type of VSWT is not sufficient enough. This paper focuses on detailed LVRT characteristic analysis of variable speed wind turbine driving a PMSG (VSWT-PMSG) with current controlled voltage source inverter (CC-VSI). Modeling and suitable control strategies for overall system are developed to augment the low voltage ride through capability of variable speed wind generator, considering recent wind farm grid code. Both symmetrical and unsymmetrical faults are analyzed as network disturbances in this paper. The permanent fault due to unsuccessful reclosing of circuit breakers is taken into consideration, which is a salient feature of this study. Moreover, the dynamic characteristic is analyzed using real wind speed data measured in Hokkaido Island, Japan. The proposed control scheme is simulated by using the standard power system simulation package PSCAD/EMTDC and results are verified by comparing that of voltage controlled voltage source inverter scheme available in power system literature.

  14. Estimates of oceanic surface wind speed and direction using orthogonal beam scatterometer measurements and comparison of recent sea scattering theories

    Science.gov (United States)

    Moore, R. K.; Fung, A. K.; Dome, G. J.; Birrer, I. J.

    1978-01-01

    The wind direction properties of radar backscatter from the sea were empirically modelled using a cosine Fourier series through the 4th harmonic in wind direction (referenced to upwind). A comparison with 1975 JONSWAP (Joint North Sea Wave Project) scatterometer data, at incidence angles of 40 and 65, indicates that effects to third and fourth harmonics are negligible. Another important result is that the Fourier coefficients through the second harmonic are related to wind speed by a power law expression. A technique is also proposed to estimate the wind speed and direction over the ocean from two orthogonal scattering measurements. A comparison between two different types of sea scatter theories, one type presented by the work of Wright and the other by that of Chan and Fung, was made with recent scatterometer measurements. It demonstrates that a complete scattering model must include some provisions for the anisotropic characteristics of the sea scatter, and use a sea spectrum which depends upon wind speed.

  15. Prognostics and Health Management of Wind Turbines: Current Status and Future Opportunities

    Energy Technology Data Exchange (ETDEWEB)

    Sheng, Shuangwen

    2016-10-04

    This presentation was given at the 2016 Annual Conference of the Prognostics and Health Management Society. It covers the current status and challenges and opportunities of prognostics and health management of wind turbines.

  16. A current controlled matrix converter for wind energy conversion systems based on permanent magnet synchronous generator

    Directory of Open Access Journals (Sweden)

    Naggar H. Saad

    2016-05-01

    Full Text Available The main challenges of wind energy conversion systems (WECS are to maximize the energy capture from the wind and injecting reactive power during the fault. This paper presents a current controlled matrix converter to interface Permanent Magnet Synchronous Generators (PMSG based WECS with the grid. To achieve fast dynamic response with reduced current ripples, a hysteresis current control is utilized. The proposed control system decouples the active and reactive components of the PMSG current to extract the maximum power from the wind at a given wind velocity and to inject reactive power to the grid. Reactive power injection during the fault satisfying the grid-codes requirement. The proposed WECS has been modeled and simulated using PSCAD/EMTDC software package.

  17. Current direction data from moored current meter casts in the North Pacific Ocean from 1984-04-24 to 1984-06-01 (NODC Accession 8500122)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction data were collected using moored current meter casts in the North Pacific Ocean from April 24, 1984 to June 1, 1984. Data were submitted by...

  18. Current meter and temperature profile data from moored current meter casts in the TOGA area - Atlantic Ocean from 10 September 1970 - 27 October 1980 (NODC Accession 8600320)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter and temperature profile data were collected using moored current meter - PCM casts in the TOGA area - Atlantic Ocean from September 10, 1970 to October...

  19. The intOA Experiment: A Study of Ocean-Atmosphere Interactions Under Moderate to Strong Offshore Winds and Opposing Swell Conditions in the Gulf of Tehuantepec, Mexico

    Science.gov (United States)

    Ocampo-Torres, F. J.; García-Nava, H.; Durazo, R.; Osuna, P.; Díaz Méndez, G. M.; Graber, H. C.

    2011-03-01

    The Gulf of Tehuantepec air-sea interaction experiment ( intOA) took place from February to April 2005, under the Programme for the Study of the Gulf of Tehuantepec (PEGoT, Spanish acronym for Programa para el Estudio del Golfo de Tehuantepec). PEGoT is underway aiming for better knowledge of the effect of strong and persistent offshore winds on coastal waters and their natural resources, as well as performing advanced numerical modelling of the wave and surface current fields. One of the goals of the intOA experiment is to improve our knowledge on air-sea interaction processes with particular emphasis on the effect of surface waves on the momentum flux for the characteristic and unique conditions that occur when strong Tehuano winds blow offshore against the Pacific Ocean long period swell. For the field campaign, an air-sea interaction spar (ASIS) buoy was deployed in the Gulf of Tehuantepec to measure surface waves and the momentum flux between the ocean and the atmosphere. High frequency radar systems (phase array type) were in operation from two coastal sites and three acoustic Doppler current profilers were deployed near-shore. Synthetic aperture radar images were also acquired as part of the remote sensing component of the experiment. The present paper provides the main results on the wave and wind fields, addressing the direct calculation of the momentum flux and the drag coefficient, and gives an overview of the intOA experiment. Although the effect of swell has been described in recent studies, this is the first time for the very specific conditions encountered, such as swell persistently opposing offshore winds and locally generated waves, to show a clear evidence of the influence on the wind stress of the significant steepness of swell waves.

  20. Interaction of additive noise and nonlinear dynamics in the double-gyre wind-driven ocean circulation

    NARCIS (Netherlands)

    Sapsis, T.; Dijkstra, H.A.

    2013-01-01

    In this paper the authors study the interactions of additive noise and nonlinear dynamics in a quasi-geostrophicmodel of the double-gyre wind-driven ocean circulation. The recently developed framework of dynamically orthogonal field theory is used to determine the statistics of the flows that arise

  1. Sea-level and ocean-current control on carbonate-platform growth, Maldives, Indian Ocean

    NARCIS (Netherlands)

    Betzler, C.; Fürstenau, J.; Lüdmann, T.; Hübscher, C.; Lindhorst, S.; Paul, A.; Reijmer, J.J.G.; Droxler, A.W.

    2013-01-01

    Multichannel high-resolution seismic and multibeam data were acquired from the Maldives-isolated carbonate platform in the Indian Ocean for a detailed characterization of the Neogene bank architecture of this edifice. The goal of the research is to decipher the controlling factors of platform

  2. Detangling Spaghetti: Tracking Deep Ocean Currents in the Gulf of Mexico

    Science.gov (United States)

    Curran, Mary Carla; Bower, Amy S.; Furey, Heather H.

    2017-01-01

    Creation of physical models can help students learn science by enabling them to be more involved in the scientific process of discovery and to use multiple senses during investigations. This activity achieves these goals by having students model ocean currents in the Gulf of Mexico. In general, oceans play a key role in influencing weather…

  3. (abstract) Ekman Pumping/Suction and Wind-Driven Ocean Circulation from ERS-1 Scatterometer Measurements Over the Arabian Sea During October 1994-October 1995

    Science.gov (United States)

    Halpern, D.; Freilich, M. H.; Weller, R. A.

    1996-01-01

    Spatial variations of the east-west and north-south components of surface wind stress are critical in studies of ocean circulation and biological-physical interactions because surface wind stress curl produces a vertical velocity in the upper ocean at the bottom of the Ekman Layer.The ERS-1 scatterometer provides reasonable coverage and direct measurements of vector of winds. Three schemes are evaluated relative to high-quality moored-bouy wind observations recorded in the central Arabian Sea, where high surface waves and high atmospheric water content during the southeast monsoon adversely affect the estimation of satellite-derived winds.

  4. Comparing the effect of low wind spead parameterization on heat fluxes in atmosphere only and coupled ocean-atmosphere simulations

    Science.gov (United States)

    Torres, Olivier; Braconnot, Pascale; Marti, Olivier

    2017-04-01

    The turbulent fluxes across the ocean/atmosphere interface represent one of the principal driving forces of the global atmospheric and oceanic circulation. Representation of these fluxes presents a challenge due to the small scale acting turbulent processes compared to the resolved scales of the models. Beyond this subgrid parameterization issue, a comprehensive understanding of the impact of air-sea interactions on the system is still lacking. We are developing a methodology to investigate how differences in the parameterizations affect the water supply of the atmospheric column in the tropics, the ocean heat content and the equator-pole redistribution of heat and water by the oceanic and atmospheric circulation. We focus on the representation of the latent heat fluxes in the tropics. We investigate how the representation of the heat transfer coefficient in weak winds affect the climate response considering both atmosphere only and ocean-atmosphere coupled simulations with the IPSL climate model. We compare simulations where the only difference is the activation of a function that increases latent heat fluxes during periods of weak wind. This allows us to isolate the behavior of the Pacific warmpool region where low winds occurs frequently. Although the heat transfer coefficients are very similar for a given parameterization between atmosphere only and ocean-atmosphere coupled simulation the surface heat fluxes are very different. We analyze in detail the ocean feedbacks and the role of the latent heat fluxes by looking at the energy transport carried out by the atmosphere considering the divergent part of the moist static energy. Differences appear between the coupled and uncoupled models due to the role of the ocean which dampens a large part of the disturbance caused by the modification of parameterization.

  5. Current meter data from moored current meter casts in the Northwest Atlantic Ocean (limit -40 W) as part of the Ocean Dumping project, 1990-05-24 to 1991-06-17 (NODC Accession 9300112)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the Northwest Atlantic Ocean (limit -40 W) from May 24, 1990 to June 17, 1991. Data were...

  6. Current meter data from moored current meter casts in the Northeast Pacific Ocean as part of the Ocean Prediction Through Observation Modeling and Analysis (OPTOMA) project, 1984-09-26 to 1985-07-16 (NODC Accession 9600075)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the Northeast Pacific Ocean from September 26, 1984 to July 16, 1985. Data were submitted by...

  7. Current meter data from moored current meter casts in the Pacific Ocean as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1979-01-20 to 1984-04-01 (NODC Accession 8700077)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the Pacific Ocean from January 20, 1979 to April 1, 1984. Data were submitted by Pacific Marine...

  8. Current meter data from moored current meter casts in the South Pacific Ocean as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1981-11-21 to 1983-11-20 (NODC Accession 8500258)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the South Pacific Ocean from November 21, 1981 to November 20, 1983. Data were submitted by...

  9. Current meter data from moored current meter casts in the Pacific Ocean as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1990-04-30 to 1991-05-15 (NODC Accession 9400005)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the Pacific Ocean from April 30, 1990 to May 15, 1991. Data were submitted by Pacific Marine...

  10. Current meter data from moored current meter casts in the Pacific Ocean as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1979-01-20 to 1984-04-26 (NODC Accession 8500007)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the Pacific Ocean from January 20, 1979 to April 26, 1984. Data were submitted by Pacific...

  11. Current meter data from moored current meter casts in the Pacific Ocean as part of the Equatorial Pacific Ocean Climate Studies (EPOCS) project from 1986-05-28 to 1987-05-11 (NODC Accession 8900168)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the Pacific Ocean from 28 May 1986 to 01 May 1983. Data were submitted by Pacific Marine...

  12. Near 7-day response of ocean bottom pressure to atmospheric surface pressure and winds in the northern South China Sea

    Science.gov (United States)

    Zhang, Kun; Zhu, Xiao-Hua; Zhao, Ruixiang

    2018-02-01

    Ocean bottom pressures, observed by five pressure-recording inverted echo sounders (PIESs) from October 2012 to July 2014, exhibit strong near 7-day variability in the northern South China Sea (SCS) where long-term in situ bottom pressure observations are quite sparse. This variability was strongest in October 2013 during the near two years observation period. By joint analysis with European Center for Medium-Range Weather Forecasts (ECMWF) data, it is shown that the near 7-day ocean bottom pressure variability is closely related to the local atmospheric surface pressure and winds. Within a period band near 7 days, there are high coherences, exceeding 95% significance level, of observed ocean bottom pressure with local atmospheric surface pressure and with both zonal and meridional components of the wind. Ekman pumping/suction caused by the meridional component of the wind in particular, is suggested as one driving mechanism. A Kelvin wave response to the near 7-day oscillation would propagate down along the continental slope, observed at the Qui Nhon in the Vietnam. By multiple and partial coherence analyses, we find that local atmospheric surface pressure and Ekman pumping/suction show nearly equal influence on ocean bottom pressure variability at near 7-day periods. A schematic diagram representing an idealized model gives us a possible mechanism to explain the relationship between ocean bottom pressure and local atmospheric forcing at near 7-day periods in the northern SCS.

  13. Azimuthally asymmetric ring current as a function of Dst and solar wind conditions

    Directory of Open Access Journals (Sweden)

    Y. P. Maltsev

    2004-09-01

    Full Text Available Based on magnetic data, spatial distribution of the westward ring current flowing at |z|<3 RE has been found under five levels of Dst, five levels of the interplanetary magnetic field (IMF z component, and five levels of the solar wind dynamic pressure Psw. The maximum of the current is located near midnight at distances 5 to 7 RE. The magnitude of the nightside and dayside parts of the westward current at distances from 4 to 9 RE can be approximated as Inight=1.75-0.041 Dst, Inoon=0.22-0.013 Dst, where the current is in MA. The relation of the nightside current to the solar wind parameters can be expressed as Inight=1.45-0.20 Bs IMF + 0.32 Psw, where BsIMF is the IMF southward component. The dayside ring current poorly correlates with the solar wind parameters.

  14. Impact of Antarctic Circumpolar Current development on late Paleogene ocean structure.

    Science.gov (United States)

    Katz, Miriam E; Cramer, Benjamin S; Toggweiler, J R; Esmay, Gar; Liu, Chengjie; Miller, Kenneth G; Rosenthal, Yair; Wade, Bridget S; Wright, James D

    2011-05-27

    Global cooling and the development of continental-scale Antarctic glaciation occurred in the late middle Eocene to early Oligocene (~38 to 28 million years ago), accompanied by deep-ocean reorganization attributed to gradual Antarctic Circumpolar Current (ACC) development. Our benthic foraminiferal stable isotope comparisons show that a large δ(13)C offset developed between mid-depth (~600 meters) and deep (>1000 meters) western North Atlantic waters in the early Oligocene, indicating the development of intermediate-depth δ(13)C and O(2) minima closely linked in the modern ocean to northward incursion of Antarctic Intermediate Water. At the same time, the ocean's coldest waters became restricted to south of the ACC, probably forming a bottom-ocean layer, as in the modern ocean. We show that the modern four-layer ocean structure (surface, intermediate, deep, and bottom waters) developed during the early Oligocene as a consequence of the ACC.

  15. Impact of shamal winds and swells on the coastal currents along the west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Samiksha, S.V.; VinodKumar, K.; Vethamony, P.

    towards north opp ose each other, resulting in intensification of currents off Ratnagiri In order to understand the intensity of shamal effect on th e existing current system, we have also analysed winds and currents before, during and after the events....

  16. The system of wind-driven seasonal coastal currents around the Indian subcontinent

    Digital Repository Service at National Institute of Oceanography (India)

    Shetye, S.R.

    implies that to understand the current at any location along the coast of India, one has to take into account wind-driving over the whole basin. The framework above applies to both seasonal currents as well as currents with periods ranging from...

  17. Wind speed variability over the Canary Islands, 1948-2014: focusing on trend differences at the land-ocean interface and below-above the trade-wind inversion layer

    Science.gov (United States)

    Azorin-Molina, Cesar; Menendez, Melisa; McVicar, Tim R.; Acevedo, Adrian; Vicente-Serrano, Sergio M.; Cuevas, Emilio; Minola, Lorenzo; Chen, Deliang

    2017-08-01

    This study simultaneously examines wind speed trends at the land-ocean interface, and below-above the trade-wind inversion layer in the Canary Islands and the surrounding Eastern North Atlantic Ocean: a key region for quantifying the variability of trade-winds and its response to large-scale atmospheric circulation changes. Two homogenized data sources are used: (1) observed wind speed from nine land-based stations (1981-2014), including one mountain weather station (Izaña) located above the trade-wind inversion layer; and (2) simulated wind speed from two atmospheric hindcasts over ocean (i.e., SeaWind I at 30 km for 1948-2014; and SeaWind II at 15 km for 1989-2014). The results revealed a widespread significant negative trend of trade-winds over ocean for 1948-2014, whereas no significant trends were detected for 1989-2014. For this recent period wind speed over land and ocean displayed the same multi-decadal variability and a distinct seasonal trend pattern with a strengthening (late spring and summer; significant in May and August) and weakening (winter-spring-autumn; significant in April and September) of trade-winds. Above the inversion layer at Izaña, we found a predominance of significant positive trends, indicating a decoupled variability and opposite wind speed trends when compared to those reported in boundary layer. The analysis of the Trade Wind Index (TWI), the North Atlantic Oscillation Index (NAOI) and the Eastern Atlantic Index (EAI) demonstrated significant correlations with the wind speed variability, revealing that the correlation patterns of the three indices showed a spatio-temporal complementarity in shaping wind speed trends across the Eastern North Atlantic.

  18. The monsoon currents in the north Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Shankar, D.; Vinayachandran, P.N.; Unnikrishnan, A.S.

    in these ?snap- 40 E 50 E 60 E 70 E 80 E 90 E 100 E 10 S 0 10 N 20 N 30 N SECC SECEACC SC EICC EC SMC SMC LH SEC SECC EC EACC SC WICC EICC WMC Schematic of circulation in the Indian Ocean GW LL SMC SMC WMC WICC July IndiaOman Somalia Sri Lanka Arabian Sea Bay... of Bengal Andaman Sea Sumatra 40 E 50 E 60 E 70 E 80 E 90 E 100 E 10 S 0 10 N 20 N 30 N January IndiaOman Somalia Sri Lanka Arabian Sea Bay of Bengal Andaman Sea Sumatra Fig. 27. Schematic representation of the circulation, as described in this paper...

  19. Surface Wind and Upper-Ocean Variability Associated with the Madden-Julian Oscillation Simulated by the Coupled Ocean-Atmosphere Mesoscale Prediction System

    Science.gov (United States)

    2013-07-01

    temperature is observed during the suppressed phase of the MJO because of the weak winds and large shortwave radiation (Weller and Anderson 1996...western PacificOceans (e.g.,Weller andAnderson 1996; Soloviev and Lukas 1997; Bellenger and Duvel 2009). The diurnal cycle of the solar radiation ...the difference in surface shortwave radiation caused by the small-scale cloud variability, which cannot be resolved by the atmospheric model. Also

  20. Structure and variability of the Leeuwin current in the south eastern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Peter, B.N.; Sreeraj, P.; VimalKumar, K.G.

    The present study analyses the structure and variability of the Leeuwin Current in the south Indian Ocean. Besides the historic hydrographic dataset various observations made during WOCE, TOGA and other experiments conducted in the study region...

  1. Shore-based Path Planning for Marine Vehicles Using a Model of Ocean Currents

    Data.gov (United States)

    National Aeronautics and Space Administration — Develop path planning methods that incorporate an approximate model of ocean currents in path planning for a range of autonomous marine vehicles such as surface...

  2. Condition monitoring of a wind turbine doubly-fed induction generator through current signature analysis

    Science.gov (United States)

    Artigao, Estefania; Honrubia-Escribano, Andres; Gomez-Lazaro, Emilio

    2017-11-01

    Operation and maintenance (O&M) of wind turbines is recently becoming the spotlight in the wind energy sector. While wind turbine power capacities continue to increase and new offshore developments are being installed, O&M costs keep raising. With the objective of reducing such costs, the new trends are moving from corrective and preventive maintenance toward predictive actions. In this scenario, condition monitoring (CM) has been identified as the key to achieve this goal. The induction generator of a wind turbine is a major contributor to failure rates and downtime where doubly-fed induction generators (DFIG) are the dominant technology employed in variable speed wind turbines. The current work presents the analysis of an in-service DFIG. A one-year measurement campaign has been used to perform the study. Several signal processing techniques have been applied and the optimal method for CM has been identified. A diagnosis has been reached, the DFIG under study shows potential gearbox damage.

  3. Ocean Bottom Seismometers technology: current state and future outlook

    Science.gov (United States)

    Ilinskiy, Dmitry; Ganzha, Oleg

    2016-04-01

    The beginning of 2000s was marked by a significant progress in the development and use of self-pop-up sea-bottom seismic recorders (Ocean Bottom Seismometers). In Russia it was a novel solution developed by the Russian Academy of Sciences Experimental Design Bureau of Oceanological Engineering. This recorder and its clones have been widely used not only for the Earth crust studies, but also for investigations of sub-basalt structures and gas hydrate exploration. And what has happened over the last 10 years? Let us look closely at the second generation of ocean bottom stations developed by Geonodal Solutions (GNS) as an illustration of the next step forward in the sea-bottom acquisition technology. First of all, hardware components have changed dramatically. The electronic components became much smaller, accordingly, the power consumption and electronic self-noise were dropped down significantly. This enabled development of compact station 330 mm in diameter instead of previous 450mm. The weight fell by half, while the autonomy increased up to 90 days due to both decreased energy consumption and increased capacity of the batteries. The dynamic range of recorded seismic data has expended as a result of decreased set noise and the application of 24-bit A/D converters. The instruments dimensions have been reduced, power consumption decreased, clock accuracy was significantly improved. At the same time, development of advanced time reference algorithms enabled to retain instrument accuracy around 1 ms during all the autonomous recording period. The high-speed wireless data transfer technology offered a chance to develop "maintenance-free" station throughout its operation time. The station can be re-used at the different sea bottom locations without unsealing of the deep-water container for data download, battery re-charge, clock synchronization. This noticeably reduces the labor efforts of the personnel working with the stations. This is critically important in field

  4. Assessing GOCE Gravity Models using Altimetry and In-situ Ocean Current Observation

    DEFF Research Database (Denmark)

    Knudsen, Per; Andersen, Ole Baltazar; Honecker, Johanna

    The Gravity and steady state Ocean Circulation Explorer (GOCE) satellite mission measures Earth's gravity field with an unprecedented accuracy at short spatial scales. Previous results have demonstrated a significant advance in our ability to determine the ocean's general circulation. The improved...... gravity models provided by the GOCE mission have enhanced the resolution and sharpened the boundaries of those features and the associated geostrophic surface currents reveal improvements for all of the ocean's current systems. In this study, a series of 23 newer gravity models including observations from...

  5. Wave modelling for the North Indian Ocean using MSMR analysed winds

    Digital Repository Service at National Institute of Oceanography (India)

    Vethamony, P.; Sudheesh, K.; Rupali, S.P.; Babu, M.T.; Jayakumar, S.; Saran, A.K.; Basu, S.K.; Kumar, R.; Sarkar, A.

    NCMRWF (National Centre for Medium Range Weather Forecast) winds assimilated with MSMR (Multi-channel Scanning Microwave Radiometer) winds are used as input to MIKE21 Offshore Spectral Wave model (OSW) which takes into account wind induced wave...

  6. The Influence of Wind on HF Radar Surface Current Forecasts

    National Research Council Canada - National Science Library

    De Almeida, Francisco M

    2008-01-01

    The ability to predict surface currents can have a beneficial impact in several activities, such as Search and Rescue and Oil Spill Response, as well as others more purely scientific, operational or economic...

  7. The most intense current sheets in the high-speed solar wind near 1 AU

    Science.gov (United States)

    Podesta, John J.

    2017-03-01

    Electric currents in the solar wind plasma are investigated using 92 ms fluxgate magnetometer data acquired in a high-speed stream near 1 AU. The minimum resolvable scale is roughly 0.18 s in the spacecraft frame or, using Taylor's "frozen turbulence" approximation, one proton inertial length di in the plasma frame. A new way of identifying current sheets is developed that utilizes a proxy for the current density J obtained from the derivatives of the three orthogonal components of the observed magnetic field B. The most intense currents are identified as 5σ events, where σ is the standard deviation of the current density. The observed 5σ events are characterized by an average scale size of approximately 3di along the flow direction of the solar wind, a median separation of around 50di or 100di along the flow direction of the solar wind, and a peak current density on the order of 0.5 pA/cm2. The associated current-carrying structures are consistent with current sheets; however, the planar geometry of these structures cannot be confirmed using single-point, single-spacecraft measurements. If Taylor's hypothesis continues to hold for the energetically dominant fluctuations at kinetic scales 1current-carrying structures in high-speed wind occur at electron scales, although the peak current densities at kinetic and electron scales are predicted to be nearly the same as those found in this study.

  8. Global Energy-saving Map of Strong Ocean Currents

    Science.gov (United States)

    2015-01-01

    Current between Taipei and Tokyo at an average speed of 12 knots. Effective use of these strong currents can yield huge savings considering that a...and the top five importers are China, United States, Japan, Taiwan, and South Korea. Overall, strong economic activities take place in the Asian Pacific...ship routers. On the route of the KC region between Tokyo and Taipei (∼ 1100 nm), ships can save 2–6% fuel with sailing speeds of around 12 knots

  9. Evaluation of wind induced currents modeling along the Southern Caspian Sea

    Science.gov (United States)

    Bohluly, Asghar; Esfahani, Fariba Sadat; Montazeri Namin, Masoud; Chegini, Fatemeh

    2018-02-01

    To improve our understanding of the Caspian Sea hydrodynamics, its circulation is simulated with special focus on wind-driven currents of its southern basin. The hydrodynamic models are forced with a newly developed fine resolution wind field to increase the accuracy of current modeling. A 2D shallow water equation model and a 3D baroclinic model are applied separately to examine the performance of each model for specific applications in the Caspian Sea. The model results are validated against recent field measurements including AWAC and temperature observations in the southern continental shelf region. Results show that the 2D model is able to well predict the depth-averaged current speed in storm conditions in narrow area of southern coasts. This finding suggests physical oceanographers apply 2D modeling as a more affordable method for extreme current speed analysis at the continental shelf region. On the other hand the 3D model demonstrates a better performance in reproducing monthly mean circulation and hence is preferable for surface circulation of Caspian Sea. Monthly sea surface circulation fields of the southern basin reveal a dipole cyclonic-anticyclonic pattern, a dominant eastward current along the southern coasts which intensifies from May to November and a dominant southward current along the eastern coasts in all months except February when the flow is northward. Monthly mean wind fields exhibit two main patterns including a north-south pattern occurring at warm months and collision of two wind fronts especially in the cold months. This collision occurs on a narrow region at the southern continental shelf regions. Due to wind field complexities, it leads to a major source of uncertainty in predicting the wind-driven currents. However, this source of uncertainty is significantly alleviated by applying a fine resolution wind field.

  10. Surface and subsurface geostrophic current variability in the Indian Ocean from altimetry

    Digital Repository Service at National Institute of Oceanography (India)

    Cadden, D.D; Subrahmanyam, B; Chambers, D; Murty, V.S.N.

    the World Ocean Atlas 2005. The results of this method were validated with currents measured using Acoustic Doppler Current Profilers moored along the equator at 77 degrees E, 83 degrees E, and 93 degrees E. The measured and computed currents compared...

  11. Station-keeping control of an unmanned surface vehicle exposed to current and wind disturbances

    OpenAIRE

    Sarda, Edoardo I.; Qu, Huajin; Bertaska, Ivan R.; von Ellenrieder, Karl D.

    2017-01-01

    Field trials of a 4 meter long, 180 kilogram, unmanned surface vehicle (USV) have been conducted to evaluate the performance of station-keeping heading and position controllers in an outdoor marine environment disturbed by wind and current. The USV has a twin hull configuration and a custom-designed propulsion system, which consists of two azimuthing thrusters, one for each hull. Nonlinear proportional derivative, backstepping and sliding mode feedback controllers were tested in winds of abou...

  12. The response of the equatorial Pacific Ocean to a westerly wind burst in May 1986

    Science.gov (United States)

    McPhaden, Michael J.; Freitag, H. Paul; Hayes, Stanley P.; Taft, Bruce A.; Chen, Zeshi; Wyrtki, Klaus

    1988-09-01

    Western Pacific westerly wind bursts of 1- to 3-week duration are potentially important in triggering and sustaining El Niño-Southern Oscillation events. One such burst of 10-day duration and maximum speeds of greater than 10 m s-1 occurred in May 1986 west of the date line. The response to this westerly wind burst is documented from equatorial current meter moorings, thermistor chain moorings, and sea level and hydrographic data. At 0°, 165°E in the western Pacific the thermocline was depressed by 25 m, sea surface temperature dropped by 0.3°-0.4°C, and sea level rose by 10-15 cm a few days after the maximum in westerly wind speed. Likewise, the South Equatorial Current rapidly accelerated eastward and attained speeds in excess of 100 cm s-1. Vertical shear in an approximately 100 m deep surface layer reversed within a few days of the winds, consistent with a simple model of equatorial mixed layer dynamics in which vertical eddy viscosities are inferred to be O(100 cm2 s-1). A sharp Kelvin wavelike pulse in sea level propagated out of the directly forced region into the central and eastern Pacific. The pulse took 45 days to travel from Tarawa (1°N, 173°E) to La Libertad (2°S, 81°W) on the South American coast, at an average phase speed of about 300 cm s-1. This is of the same order of magnitude as, but significantly higher than, the phase speed of a first baroclinic mode Kelvin wave and is probably the result of Doppler shifting by the Equatorial Undercurrent. A rise in sea surface temperature of about 1°C in 2 days occurred at 0°N, 110°W with the passage of the pulse. However, coincidental meridional advection of a sharp sea surface temperature front, rather than zonal advection of downwelling associated with the pulse, appears to be responsible for this warming. The relevance of this wind-forced pulse to the subsequent evolution of the 1986-1987 El Niño-Southern Oscillation event is discussed in the light of these observations.

  13. Diffusion in coastal and harbour zones, effects of Waves,Wind and Currents

    Science.gov (United States)

    Diez, M.; Redondo, J. M.

    2009-04-01

    As there are multiple processes at different scales that produce turbulent mixing in the ocean, thus giving a large variation of horizontal eddy diffusivities, we use a direct method to evaluate the influence of different ambient parameters such as wave height and wind on coastal dispersion. Measurements of the diffusivity are made by digital processing of images taken from from video recordings of the sea surface near the coast. The use of image analysis allows to estimate both spatial and temporal characteristics of wave fields, surface circulation and mixing in the surf zone, near Wave breakers and inside Harbours. The study of near-shore dispersion [1], with the added complexity of the interaction between wave fields, longshore currents, turbulence and beach morphology, needs detailed measurements of simple mixing processes to compare the respective influences of forcings at different scales. The measurements include simultaneous time series of waves, currents, wind velocities from the studied area. Cuantitative information from the video images is accomplished using the DigImage video processing system [3], and a frame grabber. The video may be controlled by the computer, allowing, remote control of the processing. Spectral analysis on the images has also used n order to estimate dominant wave periods as well as the dispersion relations of dominant instabilities. The measurements presented here consist mostly on the comarison of difussion coeficients measured by evaluating the spread of blobs of dye (milk) as well as by measuring the separation between different buoys released at the same time. We have used a techniques, developed by Bahia(1997), Diez(1998) and Bezerra(2000)[1-3] to study turbulent diffusion by means of digital processing of images taken from remote sensing and video recordings of the sea surface. The use of image analysis allows to measure variations of several decades in horizontal diffusivity values, the comparison of the diffusivities

  14. The OSMOSIS Model of the Wind-Driven Ocean Surface Boundary Layer.

    Science.gov (United States)

    Grant, A. L.; Belcher, S. E.; Pearson, B.; Polton, J.

    2016-02-01

    In the wind-driven ocean surface boundary layer (OSBL) the vertical velocity variance is observed to be larger than in shear driven turbulence. The observed variances are consistent with the results from large-eddy simulations (LES) which parametrize the interaction between the Stokes drift of the surface waves and vorticity. The resulting flow is known as Langmuir turbulence and the close connection between winds and waves suggests that Langmuir turbulence is common in the OSBL. This poster describes a model of the OSBL, developed as part of the OSMOSIS project, in which mixing is by Langmuir turbulence. The transports of momentum, heat and salinity are represented by a first-order closure scheme with flux-gradient relationships that include non-gradient contributions. In this the model is similar to the KPP scheme which uses flux-gradient relationships with non-gradient contributions to represent scalar transports. The flux-gradient relationships are derived from an analysis of the turbulent flux budgets of momentum and scalars (heat) obtained from LES. The non-gradient terms represent the contributions to the turbulent flux by the terms in the turbulent flux budget that represent the effects of the Stokes shear, buoyancy and turbulent transport. The eddy viscosity, diffusivities and non-gradient components are represented by similarity profiles. The depth of the boundary layer is determined by a prognostic equation, which represents the time variation of the boundary layer depth in both unstable and stable conditions. It is based on the equation for the depth integrated potential energy combined with a parametrization of the turbulent kinetic energy budget. The use of the prognostic equation allows the effects of Langmuir turbulence on boundary layer depth to be explicitly represented in the model. Comparison with the results from LES of the diurnal cycle of the OSBL are presented as a test for the model.

  15. Biogeography of the Oceans: a Review of Development of Knowledge of Currents, Fronts and Regional Boundaries from Sailing Ships in the Sixteenth Century to Satellite Remote Sensing

    Science.gov (United States)

    Priede, Imants G.

    2014-06-01

    The development of knowledge of global biogeography of the oceans from sixteenthcentury European voyages of exploration to present-day use of satellite remote sensing is reviewed in three parts; the pre-satellite era (1513-1977), the satellite era leading to a first global synthesis (1978-1998), and more recent studies since 1998. The Gulf Stream was first identified as a strong open-ocean feature in 1513 and by the eighteenth century, regular transatlantic voyages by sailing ships had established the general patterns of winds and circulation, enabling optimisation of passage times. Differences in water temperature, water colour and species of animals were recognised as important cues for navigation. Systematic collection of information from ships' logs enabled Maury (The Physical Geography of the Sea Harper and Bros. New York 1855) to produce a chart of prevailing winds across the entire world's oceans, and by the early twentieth century the global surface ocean circulation that defines the major biogeographic regions was well-known. This information was further supplemented by data from large-scale plankton surveys. The launch of the Coastal Zone Color Scanner, specifically designed to study living marine resources on board the Nimbus 7 polar orbiting satellite in 1978, marked the advent of the satellite era. Over subsequent decades, correlation of satellite-derived sea surface temperature and chlorophyll data with in situ measurements enabled Longhurst (Ecological Geography of the Sea. Academic Press, New York 1998) to divide the global ocean into 51 ecological provinces with Polar, Westerly Wind, Trade Wind and Coastal Biomes clearly recognisable from earlier subdivisions of the oceans. Satellite imagery with semi-synoptic images of large areas of the oceans greatly aided definition of boundaries between provinces. However, ocean boundaries are dynamic, varying from season to season and year to year. More recent work has focused on the study of variability of

  16. The ocean-atmosphere response to wind-induced thermocline changes in the tropical South Western Indian Ocean

    NARCIS (Netherlands)

    Manola, Iris; Selten, F. M.; De Ruijter, W. P M; Hazeleger, W.

    2014-01-01

    In the Indian Ocean basin the sea surface temperatures (SSTs) are most sensitive to changes in the oceanic depth of the thermocline in the region of the Seychelles Dome. Observational studies have suggested that the strong SST variations in this region influence the atmospheric evolution around the

  17. Validation of Sensing Ocean Surface Currents Using Multi-Frequency HF Radar Based on a Circular Receiving Array

    Directory of Open Access Journals (Sweden)

    Chen Zhao

    2018-01-01

    Full Text Available To reduce the floor space of receiving antenna arrays, the Radio Ocean Remote SEnsing (RORSE laboratory of Wuhan University developed a circular receiving array for a multi-frequency high frequency (MHF radar system in 2014, consisting of seven uniformly spaced antenna elements positioned on a circle with a diameter of 5 m. The new system, which is abbreviated MHF-C radar, adopts frequency modulated interrupted continuous wave (FMICW chirps and is capable of simultaneously operating at a maximum of four frequencies in the band of 7.5–25 MHz, and providing current, wave and wind maps every ten minutes. The phase direction-finding method is utilized to estimate the directions of the current signals, and array phase uncertainties are also taken into consideration in the signal model. This paper introduces the system in detail and investigates the performance of current measurements using MHF-C radars installed at Shengshan and Zhujiajian along the coast of the East China Sea. Radial current measurements derived from 8.27 MHz and 19.20 MHz at the same range are compared. Observations and comparisons between MHF-C radars and acoustic Doppler current profilers (ADCPs are also presented in this paper. The results preliminarily demonstrate that the MHF-C radar system is capable of maintaining the same performance for current measurements whenever it steers to any other azimuth in the coverage and has a good ability to measure currents.

  18. Symmetrical and Unsymmetrical Fault Currents of a Wind Power Plant: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Gevorgian, V.; Singh, M.; Muljadi, E.

    2011-12-01

    This paper investigates the short-circuit behavior of a wind power plant for different types of wind turbines. Both symmetrical faults and unsymmetrical faults are investigated. The size of wind power plants (WPPs) keeps getting bigger and bigger. The number of wind plants in the U.S. has increased very rapidly in the past 10 years. It is projected that in the U.S., the total wind power generation will reach 330 GW by 2030. As the importance of WPPs increases, planning engi-neers must perform impact studies used to evaluate short-circuit current (SCC) contribution of the plant into the transmission network under different fault conditions. This information is needed to size the circuit breakers, to establish the proper sys-tem protection, and to choose the transient suppressor in the circuits within the WPP. This task can be challenging to protec-tion engineers due to the topology differences between different types of wind turbine generators (WTGs) and the conventional generating units. This paper investigates the short-circuit behavior of a WPP for different types of wind turbines. Both symmetrical faults and unsymmetrical faults are investigated. Three different soft-ware packages are utilized to develop this paper. Time domain simulations and steady-state calculations are used to perform the analysis.

  19. A Review of Current Issues in State-of-Art of Wind Farm Overvoltage Protection

    Directory of Open Access Journals (Sweden)

    Ranko Goić

    2011-04-01

    Full Text Available This paper elaborates on several important outstanding issues in the state-of-art of overvoltage protection selection for modern wind farms. The lack of experience with this still-new technology, together with the inherent complexity of wind farm electrical systems, entails several unresolved issues pertinent to the topic of overvoltage protection, particularly in relation to lightning-initiated surges. Firstly, several aspects of the wind turbine lightning incidence, along with the issues related to the selection of lightning current parameters (pertinent to the wind farm overvoltage protection, are addressed in this paper. Secondly, several issues in the state-of-art models of the wind farm electrical systems—for the lightning surge analysis—are addressed and discussed. Here, a well-known ElectroMagnetic Transients Program (EMTP software package is often employed, with all of its benefits and some limitations. Thirdly, the metal-oxide surge arrester energy capability and the issues related to the selection of the surge arrester rated energy—in relation to the direct lightning strikes to wind turbines—is addressed. Finally, some general considerations concerning the overvoltage protection selection for wind farm projects, particularly regarding the installation of the metal-oxide surge arresters, are provided as well.

  20. Review of electrochemical energy conversion and storage for ocean thermal and wind energy systems

    Science.gov (United States)

    Landgrebe, A. R.; Donley, S. W.

    A literature review on electrochemical storage techniques related to ocean thermal (OTEC) and wind energy conversion systems (WECS) is presented. Battery use for WECS is foreseen because of siting size, variable capacity, quiet operation, and high efficiency; high cost and the necessity for further input voltage regulation is noted, as are prospects for technology transfer from existing programs for photovoltaic panel battery development. Fuel cells, which can run on hydrogen, ammonia, methanol, naphtha, etc., are encouraging because capacity increases are possible by simple addition of more fuel, and high thermal efficiency. Electrolytic use is seen as a cheap replacement source of electricity for metals refining and brine electrolysis. Systems of energy 'bridges' for OTEC plants, to transmit power to users, are reviewed as redox-flow, lithium-water-air, and aluminum batteries, fuel cells, electrolytic hydrogen, methane, and ammonia production, and the use of OTECs as power sources for floating factories. Directions of future research are indicated, noting that WECS will be in commercial production by 1985, while OTEC is far term, around 2025.

  1. The influence of sea ice, wind speed and marine mammals on Southern Ocean ambient sound

    Science.gov (United States)

    Menze, Sebastian; Zitterbart, Daniel P.; van Opzeeland, Ilse; Boebel, Olaf

    2017-01-01

    This paper describes the natural variability of ambient sound in the Southern Ocean, an acoustically pristine marine mammal habitat. Over a 3-year period, two autonomous recorders were moored along the Greenwich meridian to collect underwater passive acoustic data. Ambient sound levels were strongly affected by the annual variation of the sea-ice cover, which decouples local wind speed and sound levels during austral winter. With increasing sea-ice concentration, area and thickness, sound levels decreased while the contribution of distant sources increased. Marine mammal sounds formed a substantial part of the overall acoustic environment, comprising calls produced by Antarctic blue whales (Balaenoptera musculus intermedia), fin whales (Balaenoptera physalus), Antarctic minke whales (Balaenoptera bonaerensis) and leopard seals (Hydrurga leptonyx). The combined sound energy of a group or population vocalizing during extended periods contributed species-specific peaks to the ambient sound spectra. The temporal and spatial variation in the contribution of marine mammals to ambient sound suggests annual patterns in migration and behaviour. The Antarctic blue and fin whale contributions were loudest in austral autumn, whereas the Antarctic minke whale contribution was loudest during austral winter and repeatedly showed a diel pattern that coincided with the diel vertical migration of zooplankton.

  2. Current measurements from acoustic doppler current profilers (ADCP) in the southwest Atlantic Ocean from the World Ocean Circulation Experiment (WOCE) from 1991-01-03 to 1992-11-26 (NODC Accession 0087597)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data from the ADCP instruments of BE/335 and BW/333 from January 3, 1991 to November 26, 1992 collected as part of the World Ocean Circulation...

  3. Upward lightning attachment analysis on wind turbines and correlated current parameters

    DEFF Research Database (Denmark)

    Vogel, Stephan; Ishii, M.; Saito, M.

    2017-01-01

    . The dataset of video recordings and current measurements originates from the Japanese New Energy and Industrial Technology Development Organization Furthermore (NEDO) measurement campaign (2008 – 2013) which documented lightning incidences on wind turbines mainly during the winter season at the Sea of Japan.......This work provides insight in the attachment characteristics of upward initiated lightning discharges to wind turbines and their possible consequences for the lightning protection of wind turbine blades. All discharges were recorded at the Japanese coast of the Sea of Japan which is known...... for intense upward lightning activity. 172 video recordings of lightning discharges on rotating wind turbines are analysed and attachment angle, detachment angle, and the resulting angular displacement were determined. A classification between self-initiated and other-triggered upward lightning events...

  4. Roles of wind stress and thermodynamic forcing in recent trends in Antarctic sea ice and Southern Ocean SST: An ocean-sea ice model study

    Science.gov (United States)

    Kusahara, Kazuya; Williams, Guy D.; Massom, Robert; Reid, Phillip; Hasumi, Hiroyasu

    2017-11-01

    In contrast to a strong decrease in Arctic sea ice extent, overall Antarctic sea ice extent has modestly increased since 1979. Several hypotheses have been proposed for the net Antarctic sea ice expansion, including atmosphere/ocean circulation and temperature changes, sea ice-atmospheric-ocean feedback, increased precipitation, and enhanced basal meltwater from ice shelves. Concomitant with this positive trend in Antarctic sea ice, sea surface temperatures (SSTs) over the Southern Ocean south of approximately 45°S have cooled over this period. However, the mechanisms responsible for the Antarctic sea ice expansion and the SST cooling trend remain poorly defined. Here, we conduct comprehensive sensitivity experiments using a coupled ocean-sea ice model with a steady-state ice shelf component in order to investigate the main drivers of recent trends in Antarctic sea ice and SST over the Southern Ocean. The results suggest that Antarctic sea ice expansion is mostly explained by trends in the thermodynamic surface forcing, notably cooling and drying and a reduction in longwave radiation. Similarly, thermodynamic forcing is found to be the main driver of the zonal SST cooling trend. While apparently less influential on sea ice extent and SST, wind stress plays a key role in sea ice motion, thickening coastal sea ice, and thinning and decreasing the concentration of ice in mid-pack regions of the Amundsen-eastern Ross seas and 65-95°E in winter-spring. Furthermore, the model suggests that ocean-ice shelf interaction does not significantly influence the observed trends in Antarctic sea ice coverage and Southern Ocean SST in recent decades.

  5. Remote Sensing Marine Ecology: Wind-driven algal blooms in the open oceans and their ecological impacts

    Science.gov (United States)

    Tang, DanLing

    2016-07-01

    Algal bloom not only can increase the primary production but also could result in negative ecological consequence, e.g., Harmful Algal Blooms (HABs). According to the classic theory for the formation of algal blooms "critical depth" and "eutrophication", oligotrophic sea area is usually difficult to form a large area of algal blooms, and actually the traditional observation is only sporadic capture to the existence of algal blooms. Taking full advantage of multiple data of satellite remote sensing, this study: 1), introduces "Wind-driven algal blooms in open oceans: observation and mechanisms" It explained except classic coastal Ekman transport, the wind through a variety of mechanisms affecting the formation of algal blooms. Proposed a conceptual model of "Strong wind -upwelling-nutrient-phytoplankton blooms" in Western South China Sea (SCS) to assess role of wind-induced advection transport in phytoplankton bloom formation. It illustrates the nutrient resources that support long-term offshore phytoplankton blooms in the western SCS; 2), Proposal of the theory that "typhoons cause vertical mixing, induce phytoplankton blooms", and quantify their important contribution to marine primary production; Proposal a new ecological index for typhoon. Proposed remote sensing inversion models. 3), Finding of the spatial and temporaldistributions pattern of harmful algal bloom (HAB)and species variations of HAB in the South Yellow Sea and East China Sea, and in the Pearl River estuary, and their oceanic dynamic mechanisms related with monsoon; The project developed new techniques and generated new knowledge, which significantly improved understanding of the formation mechanisms of algal blooms. 1), It proposed "wind-pump" mechanism integrates theoretical system combing "ocean dynamics, development of algal blooms, and impact on primary production", which will benefit fisheries management. 2), A new interdisciplinary subject "Remote Sensing Marine Ecology"(RSME) has been

  6. Observations of C-Band Brightness Temperature and Ocean Surface Wind Speed and Rain Rate in Hurricanes Earl And Karl (2010)

    Science.gov (United States)

    Miller, Timothy; James, Mark; Roberts, Brent J.; Biswax, Sayak; Uhlhorn, Eric; Black, Peter; Linwood Jones, W.; Johnson, Jimmy; Farrar, Spencer; Sahawneh, Saleem

    2012-01-01

    Ocean surface emission is affected by: a) Sea surface temperature. b) Wind speed (foam fraction). c) Salinity After production of calibrated Tb fields, geophysical fields wind speed and rain rate (or column) are retrieved. HIRAD utilizes NASA Instrument Incubator Technology: a) Provides unique observations of sea surface wind, temp and rain b) Advances understanding & prediction of hurricane intensity c) Expands Stepped Frequency Microwave Radiometer capabilities d) Uses synthetic thinned array and RFI mitigation technology of Lightweight Rain Radiometer (NASA Instrument Incubator) Passive Microwave C-Band Radiometer with Freq: 4, 5, 6 & 6.6 GHz: a) Version 1: H-pol for ocean wind speed, b) Version 2: dual ]pol for ocean wind vectors. Performance Characteristics: a) Earth Incidence angle: 0deg - 60deg, b) Spatial Resolution: 2-5 km, c) Swath: approx.70 km for 20 km altitude. Observational Goals: WS 10 - >85 m/s RR 5 - > 100 mm/hr.

  7. Compensation for Harmonic Currents and Reactive Power in Wind Power Generation System using PWM Inverter

    Science.gov (United States)

    Shinohara, Katsuji; Shinhatsubo, Kurato; Iimori, Kenichi; Yamamoto, Kichiro; Saruban, Takamichi; Yamaemori, Takahiro

    In recent year, consciousness of environmental problems is enhancing, and the price of the electric power purchased by an electric power company is established expensive for the power plant utilizing the natural energy. So, the introduction of the wind power generation is promoted in Japan. Generally, squirrel-cage induction machines are widely used as a generator in wind power generation system because of its small size, lightweight and low-cost. However, the induction machines do not have a source of excitation. Thus, it causes the inrush currents and the instantaneous voltage drop when the generator is directly connected to a power grid. To reduce the inrush currents, an AC power regulator is used. Wind power generations are frequently connected to and disconnected from the power grid. However, when the inrush currents are reduced, harmonic currents are caused by phase control of the AC power regulator. And the phase control of AC power regulator cannot control the power factor. Therefore, we propose the use of the AC power regulator to compensate for the harmonic currents and reactive power in the wind power generation system, and demonstrate the validity of its system by simulated and experimental results.

  8. Sources, fate, and pathways of Leeuwin Current water in the Indian Ocean and Great Australian Bight : A Lagrangian study in an eddy-resolving ocean model

    NARCIS (Netherlands)

    Yit Sen Bull, Christopher; Van Sebille, Erik

    2016-01-01

    The Leeuwin Current is the dominant circulation feature in the eastern Indian Ocean, transporting tropical and subtropical water southward. While it is known that the Leeuwin Current draws its water from a multitude of sources, existing Indian Ocean circulation schematics have never quantified the

  9. Prognostics and Health Management of Wind Turbines: Current Status and Future Opportunities

    Energy Technology Data Exchange (ETDEWEB)

    Sheng, Shuangwen

    2015-12-14

    Prognostics and health management is not a new concept. It has been used in relatively mature industries, such as aviation and electronics, to help improve operation and maintenance (O&M) practices. In the wind industry, prognostics and health management is relatively new. The level for both wind industry applications and research and development (R&D) has increased in recent years because of its potential for reducing O&M cost of wind power, especially for turbines installed offshore. The majority of wind industry application efforts has been focused on diagnosis based on various sensing and feature extraction techniques. For R&D, activities are being conducted in almost all areas of a typical prognostics and health management framework (i.e., sensing, data collection, feature extraction, diagnosis, prognosis, and maintenance scheduling). This presentation provides an overview of the current status of wind turbine prognostics and health management that focuses on drivetrain condition monitoring through vibration, oil debris, and oil condition analysis techniques. It also discusses turbine component health diagnosis through data mining and modeling based on supervisory control and data acquisition system data. Finally, it provides a brief survey of R&D activities for wind turbine prognostics and health management, along with future opportunities.

  10. The measurement of winds over the ocean from Skylab with application to measuring and forecasting typhoons and hurricanes

    Science.gov (United States)

    Cardone, V. J.; Pierson, W. J.

    1975-01-01

    On Skylab, a combination microwave radar-radiometer (S193) made measurements in a tropical hurricane (AVA), a tropical storm, and various extratropical wind systems. The winds at each cell scanned by the instrument were determined by objective numerical analysis techniques. The measured radar backscatter is compared to the analyzed winds and shown to provide an accurate method for measuring winds from space. An operational version of the instrument on an orbiting satellite will be able to provide the kind of measurements in tropical cyclones available today only by expensive and dangerous aircraft reconnaissance. Additionally, the specifications of the wind field in the tropical boundary layer should contribute to improved accuracy of tropical cyclone forecasts made with numerical weather predictions models currently being applied to the tropical atmosphere.

  11. Effect of the solar wind conditions on the ionospheric equivalent current systems

    Directory of Open Access Journals (Sweden)

    J. J. Zhang

    2013-03-01

    Full Text Available We employ a global magnetohydrodynamics (MHD model, namely the PPMLR-MHD model, to investigate the effect of the solar wind conditions, such as the interplanetary magnetic field (IMF clock angle, southward IMF magnitude and solar wind speed, on the average pattern of the ionospheric equivalent current systems (ECS. A new method to derive ECS from the MHD model is proposed and applied, which takes account of the oblique magnetic field line effects. The model results indicate that when the IMF is due northward, the ECS are very weak while the current over polar region is stronger than the lower latitude; when the IMF rotates southward, the two-cell current system dominates, the eastward electrojet on the afternoon sector and the westward electrojet on the dawn sector increase rapidly while the westward electrojet is stronger than the eastward electrojet. Under southward IMF, the intensity of the westward electrojet and eastward electrojet both increase with the increase of the southward IMF magnitude and solar wind speed, and the increase is very sharp for the westward electrojet. Furthermore, we compare the geomagnetic perturbations on the ground represented by the simulated average ECS with the observation-based statistical results under similar solar wind conditions. It is found that the model results generally match with the observations, but the underestimation of the eastward equivalent current on the dusk sector is the main limitation of the present model.

  12. The Solar Wind: Our Current Understanding and How We Got Here ...

    Indian Academy of Sciences (India)

    impetus to ongoing studies of the ion-cyclotron resonance in the fast wind. After a historical review, we discuss the basic ideas behind current research, emphasizing the importance of particle kinetics. We conclude with some guesses as to how work might proceed in the future. Key words. Solar wind—coronal holes—solar ...

  13. Eddy Current Loss Modeling for Design of PM Generators for Wind Turbines

    NARCIS (Netherlands)

    Jassal, A.

    2014-01-01

    This thesis deals with analysis, calculation and validation of eddy current loss models for Permanent Magnet (PM) direct drive generators for wind turbines. The modelling approach is a mixed use of analytical and Finite Element (FE) methods. The models are validated experimentally and design

  14. The most intense electric currents in turbulent high speed solar wind

    Science.gov (United States)

    Podesta, J. J.

    2017-12-01

    Theory and simulations suggest that dissipation of turbulent energy in collisionless astrophysical plasmas occurs most rapidly in spatial regions where the current density is most intense. To advance understanding of plasma heating by turbulent dissipation in the solar corona and solar wind, it is of interest to characterize the properties of plasma regions where the current density takes exceptionally large values and to identify the operative dissipation processes. In the solar wind, the curl of the magnetic field cannot be measured using data from a single spacecraft, however, a suitable proxy for this quantity can be constructed from the spatial derivative of the magnetic field along the flow direction of the plasma. This new approach is used to study the properties of the most intense current carrying structures in a high speed solar wind stream near 1 AU. In this study, based on 11 Hz magnetometer data from the WIND spacecraft, the spatial resolution of the proxy technique is approximately equal to the proton inertial length. Intense current sheets or current carrying structures were identified as events where the magnitude of the current density exceeds μ+5σ, where μ and σ are the mean and standard deviation of the magnitude of the current density (or its proxy), respectively. Statistical studies show (1) the average size of these 5σ events is close to the smallest resolvable scale in the data set, the proton inertial length; (2) the linear distance between neighboring events follows a power law distribution; and (3) the average peak current density of 5σ events is around 1 pA/cm2. The analysis techniques used in these studies have been validated using simulated spacecraft data from three dimensional hybrid simulations which show that results based on the analysis of the proxy are qualitatively and quantitatively similar to results based on the analysis of the true current density.

  15. Role of CO2 and Southern Ocean winds in glacial abrupt climate change

    Directory of Open Access Journals (Sweden)

    M. Montoya

    2012-06-01

    Full Text Available The study of Greenland ice cores revealed two decades ago the abrupt character of glacial millennial-scale climate variability. Several triggering mechanisms have been proposed and confronted against growing proxy-data evidence. Although the implication of North Atlantic deep water (NADW formation reorganisations in glacial abrupt climate change seems robust nowadays, the final cause of these reorganisations remains unclear. Here, the role of CO2 and Southern Ocean winds is investigated using a coupled model of intermediate complexity in an experimental setup designed such that the climate system resides close to a threshold found in previous studies. An initial abrupt surface air temperature (SAT increase over the North Atlantic by 4 K in less than a decade, followed by a more gradual warming greater than 10 K on centennial timescales, is simulated in response to increasing atmospheric CO2 levels and/or enhancing southern westerlies. The simulated peak warming shows a similar pattern and amplitude over Greenland as registered in ice core records of Dansgaard-Oeschger (D/O events. This is accompanied by a strong Atlantic meridional overturning circulation (AMOC intensification. The AMOC strengthening is found to be caused by a northward shift of NADW formation sites into the Nordic Seas as a result of a northward retreat of the sea-ice front in response to higher temperatures. This leads to enhanced heat loss to the atmosphere as well as reduced freshwater fluxes via reduced sea-ice import into the region. In this way, a new mechanism that is consistent with proxy data is identified by which abrupt climate change can be promoted.

  16. Energy extraction from ocean currents using straight bladed cross-flow hydrokinetic turbine

    Directory of Open Access Journals (Sweden)

    Prasad Dudhgaonkar

    2017-04-01

    Full Text Available Harvesting marine renewable energy remains to be a prime focus of researchers across the globe both in environmental and in commercial perspectives. India is blessed with a long coastline, and the seas around Indian peninsula offer ample potential to tap various ocean energy forms. National Institute of Ocean Technology carries out research and various ocean energy technologies, out of which harnessing kinetic energy in seawater currents is one. This article presents the open sea trials recently carried out on National Institute of Ocean Technology’s cross-flow hydrokinetic ocean current turbine in South Andaman. The turbine was designed to generate 100 W electricity at 1.2 m/s current speed and was built in-house. The turbine was initially tested in a seawater channel and then was deployed in Macpherson Strait in Andaman. It was fitted below a floating platform designed especially for this purpose, and the performance of the turbine was continuously logged inside an on-board data acquisition system. The trials were successful and in line with computations.

  17. Weakest solar wind of the space age and the current 'MINI' solar maximum

    International Nuclear Information System (INIS)

    McComas, D. J.; Angold, N.; Elliott, H. A.; Livadiotis, G.; Schwadron, N. A.; Smith, C. W.; Skoug, R. M.

    2013-01-01

    The last solar minimum, which extended into 2009, was especially deep and prolonged. Since then, sunspot activity has gone through a very small peak while the heliospheric current sheet achieved large tilt angles similar to prior solar maxima. The solar wind fluid properties and interplanetary magnetic field (IMF) have declined through the prolonged solar minimum and continued to be low through the current mini solar maximum. Compared to values typically observed from the mid-1970s through the mid-1990s, the following proton parameters are lower on average from 2009 through day 79 of 2013: solar wind speed and beta (∼11%), temperature (∼40%), thermal pressure (∼55%), mass flux (∼34%), momentum flux or dynamic pressure (∼41%), energy flux (∼48%), IMF magnitude (∼31%), and radial component of the IMF (∼38%). These results have important implications for the solar wind's interaction with planetary magnetospheres and the heliosphere's interaction with the local interstellar medium, with the proton dynamic pressure remaining near the lowest values observed in the space age: ∼1.4 nPa, compared to ∼2.4 nPa typically observed from the mid-1970s through the mid-1990s. The combination of lower magnetic flux emergence from the Sun (carried out in the solar wind as the IMF) and associated low power in the solar wind points to the causal relationship between them. Our results indicate that the low solar wind output is driven by an internal trend in the Sun that is longer than the ∼11 yr solar cycle, and they suggest that this current weak solar maximum is driven by the same trend.

  18. Strongly-sheared wind-forced currents in the nearshore regions of the central Southern California Bight

    Science.gov (United States)

    Noble, Marlene A.; Rosenberger, Kurt; Robertson, George L.

    2015-01-01

    Contrary to many previous reports, winds do drive currents along the shelf in the central portion of the Southern California Bight (SCB). Winds off Huntington Beach CA are the dominant forcing for currents over the nearshore region of the shelf (water depths less than 20 m). Winds control about 50–70% of the energy in nearshore alongshelf surface currents. The wind-driven current amplitudes are also anomalously high. For a relatively weak 1 dyne/cm2 wind stress, the alongshelf surface current amplitudes in this region can reach 80 cm/s or more. Mid-depth current amplitudes for the same wind stress are around 30–40 cm/s. These wind-driven surface current amplitudes are much larger than previously measured over other nearshore shelf regions, perhaps because this program is one of the few that measured currents within a meter of the surface. The near-bed cross-shelf currents over the nearshore region of the Huntington Beach shelf have an Ekman response to winds in that they upwell (downwell) for down (up) coast winds. This response disappears further offshore. Hence, there is upwelling in the SCB, but it does not occur across the entire shelf. Subthermocline water in the nearshore region that may contain nutrients and plankton move onshore when winds are southeastward, but subthermocline water over the shelf break is not transported to the beach. The currents over the outer shelf are not predominately controlled by winds, consistent with previous reports. Instead, they are mainly driven by cross-shelf pressure gradients that are independent of local wind stress.

  19. The Relationship of High-Latitude Thermospheric Wind With Ionospheric Horizontal Current, as Observed by CHAMP Satellite

    Science.gov (United States)

    Huang, Tao; Lühr, Hermann; Wang, Hui; Xiong, Chao

    2017-12-01

    The relationship between high-latitude ionospheric currents (Hall current and field-aligned current) and thermospheric wind is investigated. The 2-D patterns of horizontal wind and equivalent current in the Northern Hemisphere derived from the CHAMP satellite are considered for the first time simultaneously. The equivalent currents show strong dependences on both interplanetary magnetic field (IMF) By and Bz components. However, IMF By orientation is more important in controlling the wind velocity patterns. The duskside wind vortex as well as the antisunward wind in the morning polar cap is more evident for positive By. To better understand their spatial relation in different sectors, a systematic superposed epoch analysis is applied. Our results show that in the dusk sector, the vectors of the zonal wind and equivalent current are anticorrelated, and both of them form a vortical flow pattern for different activity levels. The currents and zonal wind are intensified with the increase of merging electric field. However, on the dawnside, where the relation is less clear, antisunward zonal winds dominate. Plasma drift seems to play a less important role for the wind than neutral forces in this sector. In the noon sector, the best anticorrelation between equivalent current and wind is observed for a positive IMF By component and it is less obvious for negative By. A clear seasonal effect with current intensities increasing from winter to summer is observed in the noon sector. Different from the currents, the zonal wind intensity shows little dependence on seasons. Our results indicate that the plasma drift and the neutral forces are of comparable influence on the zonal wind at CHAMP altitude in the noon sector.

  20. Additional acceleration of solar-wind particles in current sheets of the heliosphere

    Directory of Open Access Journals (Sweden)

    V. Zharkova

    2015-04-01

    Full Text Available Particles of fast solar wind in the vicinity of the heliospheric current sheet (HCS or in a front of interplanetary coronal mass ejections (ICMEs often reveal very peculiar energy or velocity profiles, density distributions with double or triple peaks, and well-defined streams of electrons occurring around or far away from these events. In order to interpret the parameters of energetic particles (both ions and electrons measured by the WIND spacecraft during the HCS crossings, a comparison of the data was carried out with 3-D particle-in-cell (PIC simulations for the relevant magnetic topology (Zharkova and Khabarova, 2012. The simulations showed that all the observed particle-energy distributions, densities, ion peak velocities, electron pitch angles and directivities can be fitted with the same model if the heliospheric current sheet is in a status of continuous magnetic reconnection. In this paper we present further observations of the solar-wind particles being accelerated to rather higher energies while passing through the HCS and the evidence that this acceleration happens well before the appearance of the corotating interacting region (CIR, which passes through the spacecraft position hours later. We show that the measured particle characteristics (ion velocity, electron pitch angles and the distance at which electrons are turned from the HCS are in agreement with the simulations of additional particle acceleration in a reconnecting HCS with a strong guiding field as measured by WIND. A few examples are also presented showing additional acceleration of solar-wind particles during their passage through current sheets formed in a front of ICMEs. This additional acceleration at the ICME current sheets can explain the anticorrelation of ion and electron fluxes frequently observed around the ICME's leading front. Furthermore, it may provide a plausible explanation of the appearance of bidirectional "strahls" (field-aligned most energetic

  1. A modelling study of the influence of anomalous wind forcing over the Barents Sea on the Atlantic water flow to the Arctic Ocean in the period 1979-2004

    Science.gov (United States)

    Marciniak, Jakub; Schlichtholz, Pawel; Maslowski, Wieslaw

    2016-04-01

    Arctic climate system is influenced by oceanic heat transport with the Atlantic water (AW) streaming towards the Arctic Ocean in two branches, through the deep Fram Strait and the shallow Barents Sea. In Fram Strait, the AW submerges below the Polar surface water and then flows cyclonically along the margin of the Arctic Ocean as a subsurface water mass in the Arctic Slope Current. In contrast to the Fram Strait branch, which is the major source of heat for the Arctic Ocean, most of the heat influx to the Barents Sea through the Barents Sea opening (BSO) is passed to the atmosphere. Only cold remnants of AW outflow to the Arctic Ocean through the northeastern gate of the Barents Sea. Some AW entering the Barents Sea recirculates westward, contributing to an outflow from the Barents Sea through the BSO along the shelf slope south of Bear Island, in the Bear Island Slope Current. Even though the two-branched AW flow toward the Arctic Ocean has been known for more than a century, little is known about co-variability of heat fluxes in the two branches, its mechanisms and climatic implications. Recent studies indicate that the Bear Island Slope Current may play a role in this co-variability. Here, co-variability of the flow through the BSO and Fram Strait is investigated using a pan-Arctic coupled ice-ocean hindcast model run for the period 1979-2004 and forced with daily atmospheric data from the ECMWF. Significant wintertime co-variability between the volume transport in the Bear Island and Arctic slope currents and its link to wind forcing over the Barents Sea is confirmed. It is found that the volume transports in these currents are, however, not correlated in the annual mean and that the wintertime co-variability of these currents has no immediate effect on either the net heat flux through the BSO or the net heat flux divergence in the Barents Sea. It is shown that the main climatic effect of wind forcing over the northern Barents Sea shelf is to induce temperature

  2. Solid Waste Transportation through Ocean Currents: Marine Debris Sightings and their Waste Quantification at Port Dickson Beaches, Peninsular Malaysia

    Directory of Open Access Journals (Sweden)

    Chong Jing Yi

    2016-07-01

    Full Text Available Four beaches at Port Dickson, Peninsular Malaysia, namely Saujana Beach, Nelayan Beach, Bagan Pinang Beach and Cermin beach have been sampled for marine debris from 7th June 2014 until 26th July 2014, on every Saturday. These beaches face the Strait of Malacca with a coastline stretching 18 km each. Our observations revealed a total debris items of 13193 in those beaches. The top three items of highest frequency were cigarette butts, foamed fragments and food wrappers. Plastic debris scaled high upto 41% of the total debris. Compared to the ocean conservancy�s 2013 report of marine debris in Malaysian beaches, which was 27,005 items with in 6.44 km, the current count is slightly low. However, Malaysia was ranked 14th place among the top 20 countries in International Marine Debris Watch program. Nelayan Beach is the dirtiest beach in Port Dickson. Around 50% of the total plastic items collected are found on those beaches. The marine debris items indicated that they arrived there by land-based and ocean-based activities. High energy conditions such as wind and waves in the beaches correlated well with less debris deposition on the beaches. With debris equivalent of 4193 items/km, Malaysia harvests less solid wastes compared to Croatia, USA, Singapore and Turkey. However, a nation wide survey is needed to assess the seriousness of marine debris problem in Malaysia.

  3. Inhibition of solar wind impingement on Mercury by planetary induction currents

    International Nuclear Information System (INIS)

    Hood, L.L.; Schubert, G.

    1979-01-01

    The simple compression of a planetary magnetosphere by varying solar wind stagnation pressure is limited by currents induced in the electrically conducting parts of the planet. This inhibition is especially important for Mercury, since the radius of the electrically conducting iron core is a large fraction of the planetary radius, which in turn is a significant fraction of the subsolar magnetospheric radius b. Previous treatments of solar wind standoff distance variations at Mercury using the terrestrial analogue b 6 assumption have neglected this phenomenon. Using the lowest suggested value of the planetary dipole moment, 2.4 x 10 22 G cm 3 , we estimate that a minimum pressure of approx.38P 0 where P 0 is the external stagnation pressure in the steady state, is required to force the standoff distance down to the subsolar surface of Mercury if the pressure change persists for at least 1 day. This value is 4.3 times that which would be predicted if Mercury had no core, and it is larger than the maximum pressure predicted at Mercury's orbit (approx.25P 0 ) on the basis of hourly averaged solar wind statistics at 1 AU. Thus a direct interaction at any time of solar wind plasma with the surface of Mercury due to external compression effects alone is unlikely for solar wind conditions similar to those at present

  4. Impact of the Agulhas Return Current on the glacial Subantarctic region in the South Indian Ocean

    Science.gov (United States)

    Ikehara, M.; Crosta, X.; Manoj, M. C.

    2017-12-01

    The Southern Ocean has played an important role in the evolution of the global climate system. The Southern Ocean circulation is dominated by the Antarctic Circumpolar Current (ACC), the world's longest and largest current system. Sea ice coverage on sea surface strongly affects the climate of the Southern Hemisphere through its impacts on the energy and gas budget, on the atmospheric circulation, on the hydrological cycle, and on the biological productivity. The Agulhas Return Current (ARC) originates from the Agulhas Current, the major western boundary current in the Indian Ocean, and transports heat from subtropical to subantarctic region. It's thought that the Agulhas leakage from the Indian Ocean to the Atlantic was reduced for the last glacial due to a northward shift of the westerlies and ACC, however, there are still unknown yet how the ARC was responded to the reduced Agulhas leakage. A piston core DCR-1PC was collected from the Del Caño Rise (46°S, 44°E, 2632m), Indian sector of the Southern Ocean. Core site located in the Subantarctic region between the Subtropical Front (STF) and Subantarctic Front (SAF). Age model of the core was established by radiocarbon dating of planktic foraminifer Globorotalia bulloides and oxygen isotope stratigraphy of benthic foraminifers Cibicidoides wuellerstorfi and Melonis bareelanus. Sediment of DCR-1PC show the cyclic changes of diatom/carbonate ooze sedimentation corresponding to Southern Ocean fronts' migrations on glacial-interglacial timescales. Records of ice-rafted debris (IRD) and oxygen isotope in planktic foraminfer G. bulloides suggest that the melting of sea ice was significantly increased during the last glacial maximum (LGM) in the Subantarctic surface water. Diatom assemblage based summer SST also shows the relative warmer condition in the Subantarctic during the LGM. These results might be explained by the strong influence of the Agulhas Return Current during the LGM in the Subantarctic. The reduced

  5. Rotor current transient analysis of DFIG-based wind turbines during symmetrical voltage faults

    International Nuclear Information System (INIS)

    Ling, Yu; Cai, Xu; Wang, Ningbo

    2013-01-01

    Highlights: • We theoretically analyze the rotor fault current of DFIG based on space vector. • The presented analysis is simple, easy to understand. • The analysis highlights the accuracy of the expression of the rotor fault currents. • The expression can be widely used to analyze the different levels of voltage symmetrical fault. • Simulation results show the accuracy of the expression of the rotor currents. - Abstract: The impact of grid voltage fault on doubly fed induction generators (DFIGs), especially rotor currents, has received much attention. So, in this paper, the rotor currents of based-DFIG wind turbines are considered in a generalized way, which can be widely used to analyze the cases under different levels of voltage symmetrical faults. A direct method based on space vector is proposed to obtain an accurate expression of rotor currents as a function of time for symmetrical voltage faults in the power system. The presented theoretical analysis is simple and easy to understand and especially highlights the accuracy of the expression. Finally, the comparable simulations evaluate this analysis and show that the expression of the rotor currents is sufficient to calculate the maximum fault current, DC and AC components, and especially helps to understand the causes of the problem and as a result, contributes to adapt reasonable approaches to enhance the fault ride through (FRT) capability of DFIG wind turbines during a voltage fault

  6. Offshore renewable energies, offshore wind power marine currents and waves; Energies renouvelables en mer eolien en mer courants marins et vagues

    Energy Technology Data Exchange (ETDEWEB)

    Paillard, M. [Institut Francais de Recherche pour l' Exploitation de la Mer, 92 - Issy les Moulineaux (France); Peirano, E. [Agence de Environnement et de la Maitrise de l' Energie (ADEME), 06 - Valbonne (France)

    2004-07-01

    This colloquium aims to take stock on the development of ocean energies, mainly exploitation of offshore wind energy, but also exploitation of marine currents and waves for energy conversion by discussing their perspectives, their constraints, and their environmental and socio-economic impacts. It proposes also a review the recent methodological and technological advances. The different subjects introduced are: state of the art and prospects; resource assessments, forecasting and short-term prediction, site conditions; technical assessments, installation,decommissioning, certification; environmental impacts, social aspects and acceptability; policies, market perspectives and constraints; project developments and feedback. (A.L.B.)

  7. Remote sensing of ocean surface currents: a review of what is being observed and what is being assimilated

    OpenAIRE

    Isern-Fontanet, Jordi; Ballabrera-Poy, Joaquim; Turiel, Antonio; García-Ladona, Emilio

    2017-01-01

    Ocean currents play a key role in Earth's climate – they impact almost any process taking place in the ocean and are of major importance for navigation and human activities at sea. Nevertheless, their observation and forecasting are still difficult. First, no observing system is able to provide direct measurements of global ocean currents on synoptic scales. Consequently, it has been necessary to use sea surface height and sea surface temperature measurements and refer to dy...

  8. The artificial object detection and current velocity measurement using SAR ocean surface images

    Science.gov (United States)

    Alpatov, Boris; Strotov, Valery; Ershov, Maksim; Muraviev, Vadim; Feldman, Alexander; Smirnov, Sergey

    2017-10-01

    Due to the fact that water surface covers wide areas, remote sensing is the most appropriate way of getting information about ocean environment for vessel tracking, security purposes, ecological studies and others. Processing of synthetic aperture radar (SAR) images is extensively used for control and monitoring of the ocean surface. Image data can be acquired from Earth observation satellites, such as TerraSAR-X, ERS, and COSMO-SkyMed. Thus, SAR image processing can be used to solve many problems arising in this field of research. This paper discusses some of them including ship detection, oil pollution control and ocean currents mapping. Due to complexity of the problem several specialized algorithm are necessary to develop. The oil spill detection algorithm consists of the following main steps: image preprocessing, detection of dark areas, parameter extraction and classification. The ship detection algorithm consists of the following main steps: prescreening, land masking, image segmentation combined with parameter measurement, ship orientation estimation and object discrimination. The proposed approach to ocean currents mapping is based on Doppler's law. The results of computer modeling on real SAR images are presented. Based on these results it is concluded that the proposed approaches can be used in maritime applications.

  9. Observations of Thin Current Sheets in the Solar Wind and Their Role in Magnetic Energy Dissipation

    Science.gov (United States)

    Perri, S.; Goldstein, M. L.; Dorelli, J.; Sahraoui, F.; Gurgiolo, C. A.; Karimabadi, H.; Mozer, F.; Wendel, D. E.; TenBarge, J.; Roytershteyn, V.

    2013-12-01

    A recent analysis of 450 vec/s resolution data from the STAFF search-coil magnetometer on board Cluster has revealed, for the first time, the presence of thin current sheets and discontinuities from the proton Larmor scale down to the electron Larmor scale in the solar wind. This is in the range of scales where a cascade of energy consistent with highly oblique kinetic Alfvénic fluctuations (KAW), eventually dissipated by electron Landau damping, has been detected. The current sheets have been found to have a size between 20-200 km, indicating that they are very localized. We will compare the observations with results coming from 2D Hall MHD, Gyrokinetic, and full Particle-in-Cell turbulence simulations. Preliminary work has highlighted promising qualitative agreement between the properties of the structures observed in the Cluster data and the current sheets generated in the simulations. With the aim of investigating the role played by those structures in dissipating the magnetic energy in the solar wind, E●J has been computed within each magnetic discontinuity. This has been made possible via a combined analysis of both STAFF-SC magnetic field data and the electric field data from the Electric Fields and Wave instrument (EFW). We describe procedures used to reduce the noise in the EFW data. The results obtained represent an effort to clarify the processes involved in the dissipation of magnetic energy in the solar wind.

  10. An Application of the Peaks Over Threshold Method to Estimate Extreme Winds Over the South Atlantic Ocean

    Science.gov (United States)

    Silva, N. P.; Camargo, R. D.

    2014-12-01

    Given the growing investment in coastal activities, such as industrial and residential settings, proper understanding of oceanographic and meteorological phenomena over such areas became very important. The winds play a major role in this context, being the main source of energy for gravity waves generation in the ocean, and determining the characterization of severe weather conditions. In this study, a statistical analysis of extreme values was applied to wind data from National Centers for Environmental Prediction and National Center for Atmospheric Research reanalysis (NCEP-I) grid points with 2.5º of spacial resolution and results from a simulation with the BRAMS model in the Southwest Atlantic Ocean region with 0.25º of resolution. The Peaks Over Threshold (POT) technique was applied and the analysis focused on the behavior of extreme values according to the wind direction and the resolution of the original data. The period of analysis goes from 1982 to 2011 and the domain goes from 40ºS to 5ºN latitude and 70ºW to 10ºW longitude. The POT method demanded that peaks chosen for analysis were independent and identically distributed and a minimum interval of 48 hours was given to separate the subset sampled for analysis. The peak excesses above a determined threshold were adjusted to the Generalized Pareto Distribution and extrapolation to 50 years return periods was built in each grid point. General large-scale patterns of 50-yr return values were similar for both datasets used. However, more details were verified in the analysis of simulation results with BRAMS, given the dependence of the methodology to the resolution of the original set. Thus, the greater detailing suggests the inclusion of mesoscale features originating these extreme values. In the northern part of the domain, extreme winds were weaker and prevailed from north, northeast and east, given the influence of the trade winds and the positioning of the South Atlantic Subtropical High. On the

  11. DC Link Current Estimation in Wind-Double Feed Induction Generator Power Conditioning System

    Directory of Open Access Journals (Sweden)

    MARIAN GAICEANU

    2010-12-01

    Full Text Available In this paper the implementation of the DC link current estimator in power conditioning system of the variable speed wind turbine is shown. The wind turbine is connected to double feed induction generator (DFIG. The variable electrical energy parameters delivered by DFIG are fitted with the electrical grid parameters through back-to-back power converter. The bidirectional AC-AC power converter covers a wide speed range from subsynchronous to supersynchronous speeds. The modern control of back-to-back power converter involves power balance concept, therefore its load power should be known in any instant. By using the power balance control, the DC link voltage variation at the load changes can be reduced. In this paper the load power is estimated from the dc link, indirectly, through a second order DC link current estimator. The load current estimator is based on the DC link voltage and on the dc link input current of the rotor side converter. This method presents certain advantages instead of using measured method, which requires a low pass filter: no time delay, the feedforward current component has no ripple, no additional hardware, and more fast control response. Through the numerical simulation the performances of the proposed DC link output current estimator scheme are demonstrated.

  12. Stator Current Harmonic Reduction in a Novel Half Quasi-Z-Source Wind Power Generation System

    Directory of Open Access Journals (Sweden)

    Shoudao Huang

    2016-09-01

    Full Text Available The generator stator current gets distorted with unacceptable levels of total harmonic distortion (THD because impedance-source wind power generation systems use three-phase diode rectifiers. The stator current harmonics will cause increasing losses and torque ripple, which reduce the efficiency and stability of the system. This paper proposes a novel half quasi-Z-source inverter (H-qZSI for grid-connected wind power generation systems, which can reduce the generator stator current harmonics a great deal. When H-qZSI operates in the shoot-through zero state, the derivative of the generator stator current is only determined by the instantaneous value of the generator stator voltage, so the nonlinear relationship between generator stator current and stator voltage is improved compared with the traditional impedance-source inverter. Theoretically, it is indicated that the stator current harmonics can be reduced effectively by means of the proposed H-qZSI. Finally, simulation and experimental results are given to verify the theoretical analysis.

  13. The use of stellite scatterometer winds to drive a primitive equation model of the Indian Ocean: The impact of bandlike sampling

    Science.gov (United States)

    Barnier, Bernard; Capella, Jorge; O'Brien, James J.

    1994-01-01

    The aim of this study is to evaluate the impact of the bandlike sampling of spaceborne scatterometers on the ability of scatterometer winds to successfully force the mean flow and seasonal cycle of an ocean model in the context of equatorial and tropical dynamics. The equatorial ocean is simulated with a four-layer, primitive equation, reduced gravity model of the Indian Ocean. The variable wind stress used in this study is derived from one year (1988) of 6-hour analyses of the 10-m wind vector over the Indian Ocean performed at the European Centre for Medium-Range Weather Forecasts (ECMWF). It is applied as a forcing at every grid point of the model to drive a reference circulation. Scatterometer winds are simulated from ECMWF winds, using the nominal configurations and orbital parameters of the European Remote Sensing 1 (ERS-1) and NASA Scatterometer (NSCAT) missions. The model is forced in real time under swaths with the raw scatterometer winds of ERS-1 and NSCAT, with a persistence condition (i.e., the wind is kept constsnt until the next passage of the satellite provides a new value). The circulation obtained for each of the scatterometer experiments is compared with the reference circulation. The seasonal circulation of the Indian Ocean with NSCAT winds is very similar to the reference. The perturbations introduced by the bandlike sampling and the persistance condition have an impact similar to that of a small uncorrelated noise added to the reference forcing. The persistence condition for ERS-1 does not give results which are as good as those obtained for NSCAT.

  14. The Footprint of Continental-Scale Ocean Currents on the Biogeography of Seaweeds

    Science.gov (United States)

    Wernberg, Thomas; Thomsen, Mads S.; Connell, Sean D.; Russell, Bayden D.; Waters, Jonathan M.; Zuccarello, Giuseppe C.; Kraft, Gerald T.; Sanderson, Craig; West, John A.; Gurgel, Carlos F. D.

    2013-01-01

    Explaining spatial patterns of biological organisation remains a central challenge for biogeographic studies. In marine systems, large-scale ocean currents can modify broad-scale biological patterns by simultaneously connecting environmental (e.g. temperature, salinity and nutrients) and biological (e.g. amounts and types of dispersed propagules) properties of adjacent and distant regions. For example, steep environmental gradients and highly variable, disrupted flow should lead to heterogeneity in regional communities and high species turnover. In this study, we investigated the possible imprint of the Leeuwin (LC) and East Australia (EAC) Currents on seaweed communities across ~7,000 km of coastline in temperate Australia. These currents flow poleward along the west and east coasts of Australia, respectively, but have markedly different characteristics. We tested the hypothesis that, regional seaweed communities show serial change in the direction of current flow and that, because the LC is characterised by a weaker temperature gradient and more un-interrupted along-shore flow compared to the EAC, then coasts influenced by the LC have less variable seaweed communities and lower species turnover across regions than the EAC. This hypothesis was supported. We suggest that this pattern is likely caused by a combination of seaweed temperature tolerances and current-driven dispersal. In conclusion, our findings support the idea that the characteristics of continental-scale currents can influence regional community organisation, and that the coupling of ocean currents and marine biological structure is a general feature that transcends taxa and spatial scales. PMID:24260352

  15. H∞ Robust Current Control for DFIG Based Wind Turbine subject to Grid Voltage Distortions

    DEFF Research Database (Denmark)

    Wang, Yun; Wu, Qiuwei; Gong, Wenming

    2016-01-01

    This paper proposes an H∞ robust current controller for doubly fed induction generator (DFIG) based wind turbines (WTs) subject to grid voltage distortions. The controller is to mitigate the impact of the grid voltage distortions on rotor currents with DFIG parameter perturbation. The grid voltage...... distortions considered include asymmetric voltage dips and grid background harmonics. An uncertain DFIG model is developed with uncertain factors originating from distorted stator voltage, and changed generator parameters due to the flux saturation effect, the skin effect, etc. Weighting functions...... with a 1.5 MW DFIG model, showing its harmonics suppression ability with DFIG parameter perturbation and improved robustness....

  16. Remote sensing of ocean currents. [detection of current boundary in Gulf of Mexico through changes in sea state or ocean color

    Science.gov (United States)

    Maul, G. A. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. Fourteen field experiments in support of the NOAA investigation of ocean color boundary determination using ERTS-1 data have been conducted since June 1972. The boundary between coastal waters and the Loop Current has been detected by ERTS-1 as a result of sea state changes as well as color differences. Computer enchancement of MSS data are revealing many features not shown in the NDPF product. Analysis of the 24 channel MSS data shows that a thermal IR channel is required on an ERTS MSS to distinguish between atmospheric and sea state effects. Cloud cover analysis suggests the need for daily coverage of this type sensor for routinely useful oceanographic applications.

  17. Impact of North Atlantic Current changes on the Nordic Seas and the Arctic Ocean

    OpenAIRE

    Kauker, Frank; Gerdes, Rüdiger; Karcher, Michael; Köberle, Cornelia

    2005-01-01

    The impact of North Atlantic Current (NAC) volume, heat, and salt transport variability onto the NordicSeas and the Arctic Ocean is investigated using numerical hindcast and sensitivity experiments. Theocean-sea ice model reproduces observed propagation pathways and speeds of SST anomalies.Part of the signal reaching the entrance to the Nordic Seas between Iceland and Scotland originatesin the lower latitude North Atlantic. Response experiments with different prescribed conditionsat 50N show ...

  18. Introduction to Indian Ocean biogeochemical processes and ecological variability: Current understanding and emerging perspectives

    Digital Repository Service at National Institute of Oceanography (India)

    Wiggert, J.D.; Hood, R.R.; Naqvi, S.W.A.; Brink, K.H.; Smith, S.L.

    and underlying motivations are discussed in the monograph’s preface, while current and emerging fundamental scientific questions, as well as near- future potential for leveraging ongoing observing system in- frastructure expansion, are discussed in the closing... materialize with greater frequency. The global coverage afforded by remote sens- ing platforms, in particular the ongoing extension of ocean color-based capabilities, should also motivate more active programs of sampling in heretofore poorly characterized...

  19. Remote sensing of ocean surface currents: a review of what is being observed and what is being assimilated

    Science.gov (United States)

    Isern-Fontanet, Jordi; Ballabrera-Poy, Joaquim; Turiel, Antonio; García-Ladona, Emilio

    2017-10-01

    Ocean currents play a key role in Earth's climate - they impact almost any process taking place in the ocean and are of major importance for navigation and human activities at sea. Nevertheless, their observation and forecasting are still difficult. First, no observing system is able to provide direct measurements of global ocean currents on synoptic scales. Consequently, it has been necessary to use sea surface height and sea surface temperature measurements and refer to dynamical frameworks to derive the velocity field. Second, the assimilation of the velocity field into numerical models of ocean circulation is difficult mainly due to lack of data. Recent experiments that assimilate coastal-based radar data have shown that ocean currents will contribute to increasing the forecast skill of surface currents, but require application in multidata assimilation approaches to better identify the thermohaline structure of the ocean. In this paper we review the current knowledge in these fields and provide a global and systematic view of the technologies to retrieve ocean velocities in the upper ocean and the available approaches to assimilate this information into ocean models.

  20. Remote sensing of ocean surface currents: a review of what is being observed and what is being assimilated

    Directory of Open Access Journals (Sweden)

    J. Isern-Fontanet

    2017-10-01

    Full Text Available Ocean currents play a key role in Earth's climate – they impact almost any process taking place in the ocean and are of major importance for navigation and human activities at sea. Nevertheless, their observation and forecasting are still difficult. First, no observing system is able to provide direct measurements of global ocean currents on synoptic scales. Consequently, it has been necessary to use sea surface height and sea surface temperature measurements and refer to dynamical frameworks to derive the velocity field. Second, the assimilation of the velocity field into numerical models of ocean circulation is difficult mainly due to lack of data. Recent experiments that assimilate coastal-based radar data have shown that ocean currents will contribute to increasing the forecast skill of surface currents, but require application in multidata assimilation approaches to better identify the thermohaline structure of the ocean. In this paper we review the current knowledge in these fields and provide a global and systematic view of the technologies to retrieve ocean velocities in the upper ocean and the available approaches to assimilate this information into ocean models.

  1. Point Stabilization for an Underactuated AUV in the Presence of Ocean Currents

    Directory of Open Access Journals (Sweden)

    Zaopeng Dong

    2015-07-01

    Full Text Available This paper presents a state-feedback-based backstepping control algorithm to address the point stabilization (or set-point regulation control problem for an underactuated autonomous underwater vehicle (AUV in the presence of constant and irrotational ocean current disturbance. A nonlinear three degree of freedom dynamic model in the horizontal plane for an AUV without symmetry fore/aft is considered. The expression of the relationship between the desired heading angle of the AUV and direction angle of the ocean current, which is a necessary condition for precise point stabilization control of an underactuated AUV in the presence of ocean current disturbance is firstly discussed in this paper. The proposed backstepping control law for point stabilization has further been enriched by incorporating an additional integral action for enhancing the steady state performance of the AUV control system, while practical asymptotic stability analysis of the system is carried out using Lyapunov theory and Barbalat's Lemma. Simulation experiments of an underactuated AUV verify the theorem proposed and demonstrate the effectiveness of the controller.

  2. Wind driven currents in the Channel of São Sebastião: winter, 1979

    Directory of Open Access Journals (Sweden)

    Belmiro Mendes de Castro Fo

    1990-12-01

    Full Text Available Simultaneous 40 h low-passed wind, current and sea level data in the Channel of São Sebastião (CSS and atmospheric pressure and sea level data in the South Brazil Bight (SBB during winter of 1979 were analysed and compared. Currents in the CSS were predominantly northeastward, associated with frontal southerly winds. Current reversals occurred between meteorological disturbance passages. There were significant correlation between alongchannel components of wind and current, with a time lag of 12-18 h, wind leading; and between alongchannel component of current and sea level, with a time lag of 6-12 h, current leading. Most of the variance in the CSS series is concentrated in two frequency bands: 11-16 d and 3 d. SBB series also show high variance in those two bands. Coherences in those two bands show significant values when calculated between alongchannel components of wind and current, and sea level, in the CSS. Those three last signals were almost in phase in the 11-16 d band; and there was a lead of 16 h (25 h by wind over current (sea level in the 3 d band. There are several indications that in die subtidal band currents in the CSS are not totally locally forced.Dados simultâneos de vento, corrente e nível do mar no Canal de São Sebastião (CSS, e de pressão atmosférica e nível do mar na Plataforma Continental Sudeste (PCS, coletados durante o inverno de 1979, foram analisados e comparados. Todas as séries de tempo foram previamente filtradas utilizando um filtro passa baixa com corte em 40 h. As correntes no CSS foram predominantemente para nordeste, em associação com ventos vindos do sul juntamente com sistemas meteorológicos frontais. Reversões de corrente ocorreram entre as passagens das perturbações atmosféricas. Foram significativas as correlações entre as componentes paralelas ao canal do vento e da corrente, havendo um deslocamento de 12-18 h, com liderança do vento; e também entre a componente paralela ao canal

  3. Variable Structure Control of DFIG for Wind Power Generation and Harmonic Current Mitigation

    Directory of Open Access Journals (Sweden)

    BELMADANI, B.

    2010-11-01

    Full Text Available This paper focuses on wind energy conversion system (WECS analysis and control for power generation along with problems related to the mitigation of harmonic pollution in the grid using a variable-speed structure control of the doubly fed induction generator (DFIG. A control approach based on the so-called sliding mode control (SMC that is both efficient and suitable is used for power generation control and harmonic-current compensation. The WECS then behaves as an active power filter (APF. The method aims at improving the overall efficiency, dynamic performance and robustness of the wind power generation system. Simulation results obtained on a 20-kW, 380-V, 50-Hz DFIG confirm the effectiveness of the proposed approach.

  4. Current-Sensitive Path Planning for an Underactuated Free-Floating Ocean Sensorweb

    Science.gov (United States)

    Dahl, Kristen P.; Thompson, David R.; McLaren, David; Chao, Yi; Chien, Steve

    2011-01-01

    This work investigates multi-agent path planning in strong, dynamic currents using thousands of highly under-actuated vehicles. We address the specific task of path planning for a global network of ocean-observing floats. These submersibles are typified by the Argo global network consisting of over 3000 sensor platforms. They can control their buoyancy to float at depth for data collection or rise to the surface for satellite communications. Currently, floats drift at a constant depth regardless of the local currents. However, accurate current forecasts have become available which present the possibility of intentionally controlling floats' motion by dynamically commanding them to linger at different depths. This project explores the use of these current predictions to direct float networks to some desired final formation or position. It presents multiple algorithms for such path optimization and demonstrates their advantage over the standard approach of constant-depth drifting.

  5. Study of eddy current power loss from outer-winding coils of a magnetic position sensor

    International Nuclear Information System (INIS)

    Liu, C.-P.; Lin, T.-K.; Chang, Y.-H.; Yu, C.-S.; Wu, K.-T.; Wang, S.-J.; Ying, T.-F.; Huang, D.-R.

    2000-01-01

    The present analysis is concerned with eddy current power loss of a magnetic position sensor, which arises from a non-uniform flux linkage distribution between magnetic material and position sensor. In the paper, a magnetic position sensor system is simplified to be an outer-winding coil along the axial direction of a low carbon steel bar, and developed a numerical model to compute the electrical characteristics by an excited current source. According to the simulated and measured data in this proposed model from 2.52 to 11.37 Oes, eddy current power losses of conducting material have a variation of 6.1% and 9.77%, respectively. Finally, the phases of waveform of the induced output voltage will also be obtained in the conducting material, and have a variation of 3.68% obtained by using the current source in the proposed model

  6. Indian Moorings: Deep-sea current meter moorings in the Eastern Equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, V.S.N.; Sarma, M.S.S.; Suryanarayana, A.; Sengupta, D.; Unnikrishnan, A.S.; Fernando, V.; Almeida, A.; Khalap, S.; Sardar, A.; Somasundar, K.; Ravichandran, M.

    at the 93°E mooring location. The time-series currents data are available from the NIO website (http://www.nio.org/data_info/deep-sea_mooring/oos- deep-sea-currentmeter-moorings.htm) and are submitted to the Indian National Center for Ocean Information... System (INCOIS), Hyderabad for display at INCOIS website. The moorings will be recovered in August – September 2006 and will be redeployed at the same locations for another year. Table 1 shows the status of the current data available as of July 2006...

  7. On the internal structure of the current sheet in the pulsar wind

    Science.gov (United States)

    Prokofev, V. V.; Arzamasskiy, L. I.; Beskin, V. S.

    2018-02-01

    We investigate the internal structure of the current sheet in the pulsar wind within force-free and two-fluid MHD approximations. Within the force-free approximation we obtain general asymptotic solution of the Grad-Shafranov equation for quasi-spherical pulsar wind up to the second order in small parameter ɛ = (Ωr/c)-1. The solution allows an arbitrary latitudinal structure of the radial magnetic field, including that obtained in the numerical simulations of oblique rotators. It is also shown that the shape of the current sheet does not depend on the latitudinal structure. For the internal region of the current sheet outside the fast magnetosonic surface where the force-free approximation is not valid we use two-fluid MHD approximation. Carrying out calculations in the comoving reference frame, we succeed in determining intrinsic electric and magnetic fields of a sheet. It allows us to analyse time-dependent effects which were not investigated up to now. In particular, we estimate the efficiency of the particle acceleration inside the sheet. Finally, after investigating the motion of individual particles in the time-dependent current sheet, we find the width of the sheet and its time evolution self-consistent.

  8. Influence of Complete Coriolis Force on the Dispersion Relation of Ocean Internal-wave in a Background Currents Field

    Directory of Open Access Journals (Sweden)

    Liu Yongjun

    2015-01-01

    Full Text Available In this thesis, the influence of complete Coriolis force (the model includes both the vertical and horizontal components of Coriolis force on the dispersion relation of ocean internal-wave under background currents field are studied, it is important to the study of ocean internal waves in density-stratified ocean. We start from the control equation of sea water movement in the background of the non-traditional approximation, and the vertical velocity solution is derived where buoyancy frequency N(z gradually varies with the ocean depth z. The results show that the influence of complete Coriolis force on the dispersion relation of ocean internal-wave under background currents field is obvious, and these results provide strong evidence for the understanding of dynamic process of density stratified ocean internal waves.

  9. The value of Operational Ocean SST and Current products in glider deployments

    Science.gov (United States)

    Griffin, D.; Proctor, R.; Hollings, B.; Pattiaratchi, C.; Suthers, I.

    2009-04-01

    On November 26, 2008 a Slocum Glider was launched with the mission to explore near-shore processes off southern New South Wales, Australia, then return to the coast. This study contributed to regional activity of the Integrated Marine Observing System (www.imos.org.au), an AU100m 5-year project to establish an ocean and regional ocean observing system for Australia. The planned mission got into difficulties due to the strength of the East Australian Current and the glider began to track offshore and away from the region of interest. In order not to lose the glider to the ocean the mission was redefined to circumnavigate a warm-core eddy evident in satellite imagery. CSIRO routinely generates maps of sea surface temperature from satellite AVHRR imagery and geostrophic currents derived from sea surface height anomalies measured by satellite altimetry. By tracking the development of the SST and geostrophic circulation against the glider reported positions the satellite data helped to guide the glider into the eddy and thus continue the study, even though the satellite SST data quality was low during much of the deployment due to heavy cloud cover, and there being only two altimeters presently useful for estimating currents. The glider was successfully retrieved on December 11, 2008 40km off Jervis Bay after travelling 1002.84 km in 15 days, an average of 0.76m/s, or 1.5kt. This was achieved principally by drifting with the current, and using the glider's 0.25m/s horizontal glide velocity to go sideways with respect to the currents, to get into water thought to be going in the desired direction. The glider was saved and 2374 CTD casts produced giving a valuable dataset for understanding warm-core eddy processes, a dataset which would not have been obtained without the use of operational products.

  10. Ocean currents modify the coupling between climate change and biogeographical shifts.

    Science.gov (United States)

    García Molinos, J; Burrows, M T; Poloczanska, E S

    2017-05-02

    Biogeographical shifts are a ubiquitous global response to climate change. However, observed shifts across taxa and geographical locations are highly variable and only partially attributable to climatic conditions. Such variable outcomes result from the interaction between local climatic changes and other abiotic and biotic factors operating across species ranges. Among them, external directional forces such as ocean and air currents influence the dispersal of nearly all marine and many terrestrial organisms. Here, using a global meta-dataset of observed range shifts of marine species, we show that incorporating directional agreement between flow and climate significantly increases the proportion of explained variance. We propose a simple metric that measures the degrees of directional agreement of ocean (or air) currents with thermal gradients and considers the effects of directional forces in predictions of climate-driven range shifts. Ocean flows are found to both facilitate and hinder shifts depending on their directional agreement with spatial gradients of temperature. Further, effects are shaped by the locations of shifts in the range (trailing, leading or centroid) and taxonomic identity of species. These results support the global effects of climatic changes on distribution shifts and stress the importance of framing climate expectations in reference to other non-climatic interacting factors.

  11. Ocean Current Energy Conversion System in Wallacea Region Using Variable Speed Control Approach

    Directory of Open Access Journals (Sweden)

    Aditya Sukma Nugraha

    2012-03-01

    Full Text Available Ocean Current Energy Conversion System (OCECS is a promising green energy resource in this globe. The Thermohaline circulation data indicates that the Wallacea region has the potential of ocean current energy resources. This paper is aimed to propose research and development of OCECSs to be implemented in the Wallacea region. Firstly, four types of green energy conversion systems extracted from ocean are reviewed. Their advantages and disadvantages are discussed. Secondly, the potential of OCECS in the Wallacea region is described. Third, many types of turbines used for OCECS are reviewed and the turbine type for OCECS is selected to be implemented in the Wallacea region. Fourth, control strategy is proposed.From the work reported in this paper it is concluded that it is appropriate to implement OCECSs using axial flow water turbines in the Wallacea region, and that to maximize energy conversion variable speed control approach is selected together with control of mechanism to move the turbine vertically as well as to rotate the turbine in yaw direction. 

  12. Scales of North Atlantic wind stress curl determined from the comprehensive ocean-atmosphere data set

    Science.gov (United States)

    Ehret, Laura L.; O'Brien, James J.

    1989-01-01

    Nineteen years of wind data over the North Atlantic are used to calculate a field of wind stress curl. An empirical orthogonal function (EOF) analysis is performed on this field, resulting in spatial patterns of wind stress curl and associated time series. A Monte Carlo technique is used to establish the statistical significance of each spatial pattern, and the associated time series are spectrally analyzed. The first four statistically significant EOF modes represent more than 50 percent of the curl variance, and the spatial patterns of curl associated with these modes exhibit the major elements of North Atlantic climatology. Most of the time series spectral variance is contained in annual and semiannual frequencies. The features observed include the individual annual variation of the subtropical high and the subpolar low, the annual oscillation of intensity between pressure centers, the influence of localized strong SST gradients and associated cyclogenesis regions, and the constant nature of the trades.

  13. Spatiotemporal variability and long-term trends of ocean acidification in the California Current System

    Directory of Open Access Journals (Sweden)

    C. Hauri

    2013-01-01

    Full Text Available Due to seasonal upwelling, the upper ocean waters of the California Current System (CCS have a naturally low pH and aragonite saturation state (Ωarag, making this region particularly prone to the effects of ocean acidification. Here, we use the Regional Oceanic Modeling System (ROMS to conduct preindustrial and transient (1995–2050 simulations of ocean biogeochemistry in the CCS. The transient simulations were forced with increasing atmospheric pCO2 and increasing oceanic dissolved inorganic carbon concentrations at the lateral boundaries, as projected by the NCAR CSM 1.4 model for the IPCC SRES A2 scenario. Our results show a large seasonal variability in pH (range of ~ 0.14 and Ωarag (~ 0.2 for the nearshore areas (50 km from shore. This variability is created by the interplay of physical and biogeochemical processes. Despite this large variability, we find that present-day pH and Ωarag have already moved outside of their simulated preindustrial variability envelopes (defined by ±1 temporal standard deviation due to the rapidly increasing concentrations of atmospheric CO2. The nearshore surface pH of the northern and central CCS are simulated to move outside of their present-day variability envelopes by the mid-2040s and late 2030s, respectively. This transition may occur even earlier for nearshore surface Ωarag, which is projected to depart from its present-day variability envelope by the early- to mid-2030s. The aragonite saturation horizon of the central CCS is projected to shoal into the upper 75 m within the next 25 yr, causing near-permanent undersaturation in subsurface waters. Due to the model's overestimation of Ωarag, this transition may occur even earlier than simulated by the model. Overall, our study shows that the CCS joins the Arctic and Southern oceans as one of only a few known ocean regions presently approaching the dual threshold of

  14. Analysis of the Processes of Short-Currents Limiting by Transformer with High-Temperature Superconducting Windings

    Directory of Open Access Journals (Sweden)

    Manusov V.Z.

    2017-04-01

    Full Text Available An important advantage of transformers with high-temperature superconducting winding is their ability to limit the short-circuit currents. The article discusses a physico-mathematical model that analyses transient processes at short-circuit currents in electrical networks containing transformers with a high-temperature superconducting winding. One of the main ideas and objectives of this work is to investigate the process of short-circuit currents limiting by means of a transformer with a high-temperature superconductor winding, which makes it possible to combine two series-connected elements in one device: transformer and a reactor. The effectiveness of this method is due to the fact that when the short-circuit currents exceed the critical value of the temperature of the superconductor winding, it goes to the normal state with high winding resistance for short-circuit currents. It is important to know when a superconductor should go over to a normal state with the loss of superconductivity. For this purpose, a program was developed to determine the amount of heat generated by a short-circuit current flowing before it is disconnected. For a transformer with high-temperature superconducting winding with a capacity of 40 MVA, a short circuit must be eliminated after 0.1 seconds, without switching off the transformer. To limit the short-circuit current; it is intended to use a hybrid winding. The performed assessment showed that the return of the winding to the superconducting state, first, depends on the ratio of the short-circuit currents to the operating current. This is the criterion for the return/non-return to the superconducting state.

  15. Instability of Wind Turbine Converters during Current Injection to Low Voltage Grid Faults and PLL Frequency Based Stability Solution

    DEFF Research Database (Denmark)

    Göksu, Ömer; Teodorescu, Remus; Bak, Claus Leth

    2014-01-01

    In recent grid codes for wind power integration, wind turbines are required to stay connected during grid faults even when the grid voltage drops down to zero; and also to inject reactive current in proportion to the voltage drop. However, a physical fact, instability of grid-connected converters...... during current injection to very low (close to zero) voltage faults, has been omitted, i.e., failed to be noticed in the previous wind power studies and grid code revisions. In this paper, the instability of grid side converters of wind turbines defined as loss of synchronism (LOS), where the wind...... turbines lose synchronism with the grid fundamental frequency (e.g., 50 Hz) during very deep voltage sags, is explored with its theory, analyzed and a novel stability solution based on PLL frequency is proposed; and both are verified with power system simulations and by experiments on a grid...

  16. Analysis on the thermal and electrical characteristics of impregnating materials for the bifilar winding-type superconducting fault current limiter

    Science.gov (United States)

    Yang, Seong Eun; Bae, Duck Kweon; Yoon, Kyung Yong; Yoon, Yong Soo; Ko, Tae Kuk; Kim, Sang-Hyun

    2006-05-01

    The resistive type high temperature superconducting fault current limiter (HTSFCL) limits the fault current with the resistance that generated by fault current. The generated resistance by fault current makes large pulse power which makes the operation of HTSFCL unstable. So, the cryogenic cooling system of the resistive type HTSFCL must diffuse and eliminate the pulse energy very quickly. Although the best way is to make wide direct contact area between HTS winding and coolant as much as possible, HTS winding also need the impregnation layer which fixes and protects it from electromagnetic force. This paper deals with thermal conductivity and dielectric strength of some epoxy compounds for the impregnation of high temperature superconducting (HTS) winding at 77 K. The measured data can be used in the optimal design of impregnation for HTS winding. Aluminar filling increased the thermal conductivity of epoxy compounds. Hardener also affected the thermal conductivity and the dielectric strength of epoxy compounds.

  17. Impact of data assimilation on ocean current forecasts in the Angola Basin

    Science.gov (United States)

    Phillipson, Luke; Toumi, Ralf

    2017-06-01

    The ocean current predictability in the data limited Angola Basin was investigated using the Regional Ocean Modelling System (ROMS) with four-dimensional variational data assimilation. Six experiments were undertaken comprising a baseline case of the assimilation of salinity/temperature profiles and satellite sea surface temperature, with the subsequent addition of altimetry, OSCAR (satellite-derived sea surface currents), drifters, altimetry and drifters combined, and OSCAR and drifters combined. The addition of drifters significantly improves Lagrangian predictability in comparison to the baseline case as well as the addition of either altimetry or OSCAR. OSCAR assimilation only improves Lagrangian predictability as much as altimetry assimilation. On average the assimilation of either altimetry or OSCAR with drifter velocities does not significantly improve Lagrangian predictability compared to the drifter assimilation alone, even degrading predictability in some cases. When the forecast current speed is large, it is more likely that the combination improves trajectory forecasts. Conversely, when the currents are weaker, it is more likely that the combination degrades the trajectory forecast.

  18. Stohastic Model for Loads on Offshore Structures from Wave, Wind, Current and Water Elevation

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Sterndorff, M.J.

    2002-01-01

    For code-based LRFD and for reliability-based assessment of offshore structures such as steel platforms it is essential that consistent stochastic models for the main metocean parameters are available. The most important metocean parameters are the significant wave height, maximum individual wave...... height, maximum crest height, wind speed, current speed and water elevation. In this paper a consistent stochastic model for these parameters is formulated, where the relevant directional dependence is included. For code-based LRFD assessment it is shown how the stochastic models can be used to determine...

  19. Recent studies on wind seas and swells in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Vethamony, P.; Rashmi, R.; Samiksha, S.V.; Aboobacker, V.M.

    Winds and waves measured at a few locations along the west coast of India were analysed to study the wave characteristics in the deep as well as near shore regions during different seasons. The potential generation of swells observed in the Arabian...

  20. IFREMER-ADEME colloquium 'Offshore renewable energies: offshore wind energy - sea currents and waves. Collection of abstracts

    International Nuclear Information System (INIS)

    2004-10-01

    This document contains programme and abstracts of contributions presented during a colloquium. These contributions first addresses the context, and regulatory and economic aspects of offshore wind and sea energy: specificities related to the Public Maritime Domain for the implantation of offshore wind turbines, economy of sea energies within a perspective of de-carbonation of the world energy sector, case of offshore wind turbines and assessment of economic impacts of the implantation of sea renewable energy production units, financing stakes for offshore wind energy projects. A second set of contribution addresses the state-of -the-art and feedbacks for offshore wind energy installations. The third set addresses the assessment of resource potential, measurements, models and production prediction for offshore wind energy: case of French coasts, use of radar for remote sensing, wind climatology modelling, data acquisition for wind farm and data processing. The fourth set of contributions addresses the state-of-the-art, feedback, and R and D for sea current energy, while the fifth one addressed the same aspects for sea wave energy. Technology, installations, maintenance and storage in the field of wind energy are then addressed, and the last set deals with environmental and social-economical impacts of sea renewable energies

  1. Ensemble-Based Estimates of the Predictability of Wind-Driven Coastal Ocean Flow Over Topography

    Science.gov (United States)

    2008-01-01

    introduced in geophysi- cal fluid dynamics to quantify predictive information content in forecast ensembles (Kleeman 2002; Abramov et al. 2005). Here, we...National Ocean Partnership Program. 33 REFERENCES Abramov , R., A. Majda, and R. Kleeman, 2005: Information theory and predictability for low-frequency

  2. Multiscale Stuart-Landau Emulators: Application to Wind-Driven Ocean Gyres

    Directory of Open Access Journals (Sweden)

    Dmitri Kondrashov

    2018-03-01

    Full Text Available The multiscale variability of the ocean circulation due to its nonlinear dynamics remains a big challenge for theoretical understanding and practical ocean modeling. This paper demonstrates how the data-adaptive harmonic (DAH decomposition and inverse stochastic modeling techniques introduced in (Chekroun and Kondrashov, (2017, Chaos, 27, allow for reproducing with high fidelity the main statistical properties of multiscale variability in a coarse-grained eddy-resolving ocean flow. This fully-data-driven approach relies on extraction of frequency-ranked time-dependent coefficients describing the evolution of spatio-temporal DAH modes (DAHMs in the oceanic flow data. In turn, the time series of these coefficients are efficiently modeled by a family of low-order stochastic differential equations (SDEs stacked per frequency, involving a fixed set of predictor functions and a small number of model coefficients. These SDEs take the form of stochastic oscillators, identified as multilayer Stuart–Landau models (MSLMs, and their use is justified by relying on the theory of Ruelle–Pollicott resonances. The good modeling skills shown by the resulting DAH-MSLM emulators demonstrates the feasibility of using a network of stochastic oscillators for the modeling of geophysical turbulence. In a certain sense, the original quasiperiodic Landau view of turbulence, with the amendment of the inclusion of stochasticity, may be well suited to describe turbulence.

  3. Ocean Circulation

    OpenAIRE

    Thompson, Andrew F.; Rahmstorf, Stefan

    2009-01-01

    The ocean moderates the Earth's climate due to its vast capacity to store and transport heat; the influence of the large-scale ocean circulation on changes in climate is considered in this chapter. The ocean experiences both buoyancy forcing (through heating/cooling and evaporation/precipitation) and wind forcing. Almost all ocean forcing occurs at the surface, but these changes are communicated throughout the entire depth of the ocean through the meridional overturning circulation (MOC). In ...

  4. On stochastic stability of regional ocean models with uncertainty in wind forcing

    Directory of Open Access Journals (Sweden)

    L. M. Ivanov

    2007-10-01

    Full Text Available A shallow-water model was used to understand model error induced by non-Gaussian wind uncertainty. Although the model was simple, it described a generic system with many degrees of freedom randomized by external noise. The study focused on the nontrivial collective behavior of finite-amplitude perturbations on different scales and their influence on model predictability. The error growth strongly depended on the intensity and degree of spatial inhomogeneity of wind perturbations. For moderate but highly inhomogeneous winds, the error grew as a power law. This behavior was a consequence of varying local characteristic exponents and nonlinear interactions between different scales. Coherent growth of perturbations was obtained for different scales at various stages of error evolution. For the nonlinear stage, statistics of prediction error could be approximated by a Weibull distribution. An approach based on the Kullback-Leibler distance (the relative entropy and probability-weighted moments was developed for identification of Weibull statistics. Bifurcations of the variance, skewness and kurtosis of the irreversible predictability time (a measure of model prediction skill were detected when the accepted prediction accuracy (tolerance exceeded some threshold.

  5. Ocean current velocity, temperature and salinity collected during 2010 and 2011 in Vieques Sound and Virgin Passage (NODC Accession 0088063)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Nortek 600kHz Aquadopp acoustic current profilers were deployed between March 2010 and April 2011 on shallow water moorings located in Vieques Sound, Puerto Rico,...

  6. Current meter data collected from a fixed platform in TOGA Area - Pacific Ocean from 15 June 1980 to 16 December 1981 (NODC Accession 9400104)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using current meter in the TOGA Area - Pacific Ocean from a fixed platform. Data were collected from 15 June 1980 to 16 December...

  7. Prediction of tropical cyclone over North Indian Ocean using WRF model: sensitivity to scatterometer winds, ATOVS and ATMS radiances

    KAUST Repository

    Dodla, Venkata B.

    2016-05-03

    Tropical cyclone prediction, in terms of intensification and movement, is important for disaster management and mitigation. Hitherto, research studies were focused on this issue that lead to improvement in numerical models, initial data with data assimilation, physical parameterizations and application of ensemble prediction. Weather Research and Forecasting (WRF) model is the state-of-art model for cyclone prediction. In the present study, prediction of tropical cyclone (Phailin, 2013) that formed in the North Indian Ocean (NIO) with and without data assimilation using WRF model has been made to assess impacts of data assimilation. WRF model was designed to have nested two domains of 15 and 5 km resolutions. In the present study, numerical experiments are made without and with the assimilation of scatterometer winds, and radiances from ATOVS and ATMS. The model performance was assessed in respect to the movement and intensification of cyclone. ATOVS data assimilation experiment had produced the best prediction with least errors less than 100 km up to 60 hours and producing pre-deepening and deepening periods accurately. The Control and SCAT wind assimilation experiments have shown good track but the errors were 150-200 km and gradual deepening from the beginning itself instead of sudden deepening.

  8. Adaptive Hysteresis Band Current Control (AHB) with PLL of Grid Side Converter-Based Wind Power Generation System

    DEFF Research Database (Denmark)

    Guo, Yougui; Zeng, Ping; Li, Lijuan

    2011-01-01

    Adaptive hysteresis band current control(AHB CC) is used to control the three-phase grid currents by means of grid side converter in wind power generation system in this paper. AHB has reached the good purpose with PLL (Lock phase loop). First the mathematical models of each part are given. Then ......, transformer and grid, and control parts, etc. The simulation results have verified that the control strategy is feasible to fit for control of gird currents, active power, reactive power and DC-link voltage in wind power generation system.......Adaptive hysteresis band current control(AHB CC) is used to control the three-phase grid currents by means of grid side converter in wind power generation system in this paper. AHB has reached the good purpose with PLL (Lock phase loop). First the mathematical models of each part are given...

  9. Ocean Acidification: a review of the current status of research and institutional developments

    NARCIS (Netherlands)

    Beek, van I.J.M.; Dedert, M.

    2012-01-01

    Ocean acidification is defined as the change in ocean chemistry driven by the oceanic uptake of chemical inputs to the atmosphere, including carbon, nitrogen and sulphur compounds. Ocean acidification is also referred to as ‘the other CO2 problem’ of anthropogenic carbon dioxide (CO2) emissions

  10. Marine Benthic Habitats and Seabed Suitability Mapping for Potential Ocean Current Energy Siting Offshore Southeast Florida

    Directory of Open Access Journals (Sweden)

    Amanda Mulcan

    2015-05-01

    Full Text Available This study examines the legal framework for ocean current energy policy and regulation to develop a metric for assessing the biological and geological characteristics of a seabed area with respect to the siting of OCE devices, a framework of criteria by which to assess seabed suitability (seabed suitability framework that can facilitate the siting, and implementation of ocean current energy (OCE projects. Seafloor geology and benthic biological data were analyzed in conjunction with seafloor core sample geostatistical interpolation to locate suitable substrates for OCE anchoring. Existing submarine cable pathways were considered to determine pathways for power transmission cables that circumvent biologically sensitive areas. Suitability analysis indicates that areas east of the Miami Terrace and north of recently identified deep-sea coral mounds are the most appropriate for OCE siting due to abundance of sand/sediment substrate, existing underwater cable route access, and minimal biological presence (i.e., little to no benthic communities. Further reconnaissance requires higher resolution maps of geological substrate and benthic community locations to identify specific OCE development locations, classify benthic conditions, and minimize potentially negative OCE environmental impacts.

  11. Modelling rogue waves through exact dynamical lump soliton controlled by ocean currents

    Science.gov (United States)

    Kundu, Anjan; Mukherjee, Abhik; Naskar, Tapan

    2014-01-01

    Rogue waves are extraordinarily high and steep isolated waves, which appear suddenly in a calm sea and disappear equally fast. However, though the rogue waves are localized surface waves, their theoretical models and experimental observations are available mostly in one dimension, with the majority of them admitting only limited and fixed amplitude and modular inclination of the wave. We propose two dimensions, exactly solvable nonlinear Schrödinger (NLS) equation derivable from the basic hydrodynamic equations and endowed with integrable structures. The proposed two-dimensional equation exhibits modulation instability and frequency correction induced by the nonlinear effect, with a directional preference, all of which can be determined through precise analytic result. The two-dimensional NLS equation allows also an exact lump soliton which can model a full-grown surface rogue wave with adjustable height and modular inclination. The lump soliton under the influence of an ocean current appears and disappears preceded by a hole state, with its dynamics controlled by the current term. These desirable properties make our exact model promising for describing ocean rogue waves. PMID:24711719

  12. In-situ water current velocity measurements collected from moored current meters in the Agulhas Current region of the Indian Ocean from 2010-04-08 to 2013-02-23 (NCEI Accession 0156669)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data package is comprised of two sets of discrete in-situ current velocity measurements from the Agulhas Current Timeseries mooring array, from April 2010 to...

  13. Current meter data from moored current meter casts in the North Atlantic Ocean as part of the Outer Continental Shelf - South Atlantic (OCS-South Atlantic) project from 1980-08-26 to 1981-03-01 (NODC Accession 8100540)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the North Atlantic Ocean from August 26, 1980 to March 1, 1980. Data were submitted by Science...

  14. Current meter data from moored current meter casts in the North Atlantic Ocean as part of the Outer Continental Shelf - South Atlantic (OCS-South Atlantic) project from 1981-03-15 to 1981-10-01 (NODC Accession 8100718)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the North Atlantic Ocean from March 15, 1981 to October 1, 1981. Data were submitted by Science...

  15. Current meter data from moored current meter casts in the North Atlantic Ocean as part of the Outer Continental Shelf - South Atlantic (OCS-South Atlantic) project from 1981-06-02 to 1981-10-01 (NODC Accession 8200061)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the North Atlantic Ocean from June 2, 1981 to October 1, 1981. Data were submitted by Science...

  16. Current meter data from moored current meter casts in the North Atlantic Ocean as part of the Outer Continental Shelf - South Atlantic (OCS-South Atlantic) project from 1981-05-11 to 1981-11-01 (NODC Accession 8200003)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the North Atlantic Ocean from May 11, 1981 to November 1, 1981. Data were submitted by Science...

  17. Current meter data from moored current meter casts and other instruments in the Northwest and Southwest Pacific Ocean from 01 October 1992 to 15 March 1993 (NODC Accession 9400088)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts and other instruments in the Northwest and Southwest Pacific Ocean from October 1, 1992 to March...

  18. Current meter data from moored current meter casts in the North Atlantic Ocean as part of the Outer Continental Shelf - South Atlantic (OCS-South Atlantic) project from 1977-09-02 to 1977-11-02 (NODC Accession 7900074)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the North Atlantic Ocean from September 2, 1977 to November 2, 1977. Data were submitted by...

  19. Current meter data from moored current meter casts in the North Atlantic Ocean as part of the Outer Continental Shelf - South Atlantic (OCS-South Atlantic) project from 1978-08-01 to 1979-03-20 (NODC Accession 7900312)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the North Atlantic Ocean from August 1, 1978 to March 20, 1979. Data were submitted by Science...

  20. Current meter data from moored current meter casts and other instruments in the TOGA Area - Pacific Ocean (30 N to 30 S) from 1992-01-01 to 1993-02-17 (NODC Accession 9600019)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts and other instruments in the TOGA Area - Pacific Ocean (30 N to 30 S) from January 1, 1992 to...

  1. Current meter data from moored current meter casts in the Northeast Pacific Ocean as part of the Flow Over Abrupt Topography project from 1990-01-06 to 1991-12-03 (NODC Accession 9500077)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the Northeast Pacific Ocean from January 6, 1990 to December 3, 1991. Data were submitted by...

  2. Current meter data from moored current meter casts and other instruments in the TOGA Area - Pacific Ocean (30 N to 30 S) from 1992-11-03 to 1992-12-05 (NODC Accession 9600018)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts and other instruments in the TOGA Area - Pacific Ocean (30 N to 30 S) from November 3, 1992 to...

  3. Current meter data from moored current meter casts in the North Atlantic Ocean as part of the High Energy Benthic Boundary Exp. (HEBBLE) project from 1983-03-19 to 1984-08-01 (NODC Accession 8900107)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the North Atlantic Ocean from March 19, 1983 to August 1, 1984. Data were submitted by Woods...

  4. Current direction, temperature, and conductivity data from moored current meter casts in the North Pacific Ocean from 1981-04-29 to 1981-12-02 (NODC Accession 8300030)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction, temperature, and conductivity data were collected using moored current meter casts in the North Pacific Ocean from April 29, 1981 to December 2,...

  5. Current direction and CTD data from moored current meter and CTD casts in the Atlantic Ocean from 1980-08-04 to 1981-08-14 (NODC Accession 8200240)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction and CTD data were collected using moored current meter and CTD casts in the Atlantic Ocean from August 4, 1980 to August 14, 1981. Data were...

  6. Current direction and CTD data from moored current meter and CTD casts in the North Pacific Ocean from 1979-02-05 to 1980-12-01 (NODC Accession 8300042)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current direction and CTD data were collected using moored current meter and CTD casts in the North Pacific Ocean from February 5, 1979 to December 1, 1980. Data...

  7. Current meter and temperature profile data from current meter and buoy casts in the TOGA area of Pacific Ocean from 27 April 1993 to 09 June 1994 (NODC Accession 9700042)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter and temperature profile data were collected using current meter and buoy casts in the TOGA area of Pacific Ocean from 27 April 1993 to 09 June 1994....

  8. Current meter and other data from current meter casts from NOAA Ship RESEARCHER in the North and South Pacific Ocean from 1984-06-28 to 1984-07-01 (NODC Accession 8500226)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter and other data were collected using current meter casts from NOAA Ship RESEARCHER in the North/South Pacific Ocean from June 28, 1984 to July 1, 1984....

  9. Five-Phase Five-Level Open-Winding/Star-Winding Inverter Drive for Low-Voltage/High-Current Applications

    DEFF Research Database (Denmark)

    Padmanaban, Sanjeevi Kumar; Blaabjerg, Frede; Wheeler, Patrick

    2016-01-01

    for open-/star-winding loads. Elaborately, per phase of the VSI is built with one additional bi-directional switch (MOSFET/IGBT) and all five legs links to the neutral through two capacitors. The structure allows multilevel generation to five-level output with greater potential for fault tolerability under...

  10. VM-ADCP measured upper ocean currents in the southeastern Arabian Sea and Equatorial Indian Ocean during December, 2000

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, V.S.N.; Suryanarayana, A.; Somayajulu, Y.K.; Raikar, V.; Tilvi, V.

    of 80 degrees E. It attains higher speed (more than 50 cm/s) outside the Gulf of Mannar augmented by the strong northeasterly winds blowing over the Gulf. With the eastward flow north of 7 degrees N towards the Gulf, a clockwise eddy (early stage...

  11. Corrosion Protection Systems and Fatigue Corrosion in Offshore Wind Structures: Current Status and Future Perspectives

    Directory of Open Access Journals (Sweden)

    Seth J. Price

    2017-02-01

    Full Text Available Concerns over reducing CO2 emissions associated with the burning of fossil fuels in combination with an increase in worldwide energy demands is leading to increased development of renewable energies such as wind. The installation of offshore wind power structures (OWS is one of the most promising approaches for the production of renewable energy. However, corrosion and fatigue damage in marine and offshore environments are major causes of primary steel strength degradation in OWS. Corrosion can reduce the thickness of structural components which may lead towards fatigue crack initiation and buckling. These failure mechanisms affect tower service life and may result in catastrophic structural failure. Additionally, environmental pollution stemming from corrosion’s by-products is possible. As a result, large financial investments are made yearly for both the prevention and recovery of these drawbacks. The corrosion rate of an OWS is dependent on different characteristics of attack which are influenced by access to oxygen and humidity. Structural degradation can occur due to chemical attack, abrasive action of waves, and microorganism attacks. Inspired by technological and scientific advances in recent years, the purpose of this paper is to discuss the current protective coating system technologies used to protect OWS as well as future perspectives.

  12. Low Voltage Ride-through in DFIG Wind Generators by Controlling the Rotor Current without Crowbars

    Directory of Open Access Journals (Sweden)

    Jaime Rodríguez Arribas

    2014-01-01

    Full Text Available Among all the different types of electric wind generators, those that are based on doubly fed induction generators, or DFIG technology, are the most vulnerable to grid faults such as voltage sags. This paper proposes a new control strategy for this type of wind generator, that allows these devices to withstand the effects of a voltage sag while following the new requirements imposed by grid operators. This new control strategy makes the use of complementary devices such as crowbars unnecessary, as it greatly reduces the value of currents originated by the fault. This ensures less costly designs for the rotor systems as well as a more economic sizing of the necessary power electronics. The strategy described here uses an electric generator model based on space-phasor theory that provides a direct control over the position of the rotor magnetic flux. Controlling the rotor magnetic flux has a direct influence on the rest of the electrical variables enabling the machine to evolve to a desired work point during the transient imposed by the grid disturbance. Simulation studies have been carried out, as well as test bench trials, in order to prove the viability and functionality of the proposed control strategy.

  13. Analytical method of seafloor crustal deformation corresponding to the large scale ocean current region

    Science.gov (United States)

    Yasuda, K.; Tadokoro, K.; Matsuhiro, K.

    2015-12-01

    We monitor seafloor crustal deformation at two observation points (south and north of Nankai Trough (TOA and TCA)) across the Nankai Trough, Japan, from 2013 to 2015. A ocean current flows frequently above our points called the Kuroshio current that has temperature difference perpendicular to the flow axis down to 1000 m in depths. Sound speed in the water depends on temperature (Del Grosso, 1974). Determination of seafloor benchmark position (SBP) has a bias when the sound speed structure includes a horizontal inhomogeneity (HI) in large-scale ocean current area. This bias is caused by trade-off between estimated spatial-temporal variation of sound speed structure and SBP. In this study, we propose a new observation system and analytical method, which directly observe the HI of sound speed derived from Underway CTD (UCTD) measurement and we introduce the HI to analytical method. We performed the observation in May 2015. We measured acoustic ranging during marine navigation on a circle with radius of 2 miles. At the same time, we observed six UCTD measurements down to 700 m in depths at both points. We use analytical method of Ikuta et al. (2008) for determination of SBP and adopt estimated HI of sound speed structure from UCTD measurements. We use the following equation to adopt the HI model: S(t,x,X)=S(t)+ΔS(R(X)+ar(x,X)), where S(t,x,X) is the spatial-temporal variation of slowness but spatial variation is the uniform during the observation period, S(t) is the estimated temporal variation of sound speed structure following Ikuta et al. (2008), ΔS is the horizontal gradient of slowness estimated from UCTD measurement, R(x) is the distance of a ship from center of three SBPs, r(x,X) is the distance between ship position and benchmark position, a is the ratio of layer of HI for the whole depth, x is the ship position, and X is the benchmark position. SBP adopted the HI model is determined 74.9 cm toward N17.4˚E at TCA and 90.0 cm toward N7.8˚E at TOA. The

  14. Physical, currents, nutrients, and other data from bottle and GEK casts from the FUJI and SHIRASE in the Indian Ocean, North Pacific Ocean, South Pacific Ocean, and Southern Oceans (> 60 degrees South) from 06 December 1965 to 10 January 1994 (NODC Accession 0000039)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Physical, currents, nutrients, and other data were collected from bottle and GEK casts from the FUJI and SHIRASE in the Indian Ocean and other locations from 06...

  15. Detection of stator winding faults in induction motors using three-phase current monitoring.

    Science.gov (United States)

    Sharifi, Rasool; Ebrahimi, Mohammad

    2011-01-01

    The objective of this paper is to propose a new method for the detection of inter-turn short circuits in the stator windings of induction motors. In the previous reported methods, the supply voltage unbalance was the major difficulty, and this was solved mostly based on the sequence component impedance or current which are difficult to implement. Some other methods essentially are included in the offline methods. The proposed method is based on the motor current signature analysis and utilizes three phase current spectra to overcome the mentioned problem. Simulation results indicate that under healthy conditions, the rotor slot harmonics have the same magnitude in three phase currents, while under even 1 turn (0.3%) short circuit condition they differ from each other. Although the magnitude of these harmonics depends on the level of unbalanced voltage, they have the same magnitude in three phases in these conditions. Experiments performed under various load, fault, and supply voltage conditions validate the simulation results and demonstrate the effectiveness of the proposed technique. It is shown that the detection of resistive slight short circuits, without sensitivity to supply voltage unbalance is possible. Copyright © 2010 ISA. Published by Elsevier Ltd. All rights reserved.

  16. Risks of ocean acidification in the California Current food web and fisheries: ecosystem model projections.

    Science.gov (United States)

    Marshall, Kristin N; Kaplan, Isaac C; Hodgson, Emma E; Hermann, Albert; Busch, D Shallin; McElhany, Paul; Essington, Timothy E; Harvey, Chris J; Fulton, Elizabeth A

    2017-04-01

    The benefits and ecosystem services that humans derive from the oceans are threatened by numerous global change stressors, one of which is ocean acidification. Here, we describe the effects of ocean acidification on an upwelling system that already experiences inherently low pH conditions, the California Current. We used an end-to-end ecosystem model (Atlantis), forced by downscaled global climate models and informed by a meta-analysis of the pH sensitivities of local taxa, to investigate the direct and indirect effects of future pH on biomass and fisheries revenues. Our model projects a 0.2-unit drop in pH during the summer upwelling season from 2013 to 2063, which results in wide-ranging magnitudes of effects across guilds and functional groups. The most dramatic direct effects of future pH may be expected on epibenthic invertebrates (crabs, shrimps, benthic grazers, benthic detritivores, bivalves), and strong indirect effects expected on some demersal fish, sharks, and epibenthic invertebrates (Dungeness crab) because they consume species known to be sensitive to changing pH. The model's pelagic community, including marine mammals and seabirds, was much less influenced by future pH. Some functional groups were less affected to changing pH in the model than might be expected from experimental studies in the empirical literature due to high population productivity (e.g., copepods, pteropods). Model results suggest strong effects of reduced pH on nearshore state-managed invertebrate fisheries, but modest effects on the groundfish fishery because individual groundfish species exhibited diverse responses to changing pH. Our results provide a set of projections that generally support and build upon previous findings and set the stage for hypotheses to guide future modeling and experimental analysis on the effects of OA on marine ecosystems and fisheries. © 2017 John Wiley & Sons Ltd.

  17. Finite Element Analysis and Experimental Validation of Eddy Current Losses in Permanent Magnet Machines with Fractional-Slot Concentrated Windings

    NARCIS (Netherlands)

    Wang, X.; Liu, D.; Lahaye, D.J.P.; Polinder, H.; Ferreira, J.A.

    2016-01-01

    Permanent-magnet machines with fractional slot concentrated windings are easy to manufacture. Their popularity therefore is steadily increasing. Without a proper design, however, the induced eddy-current losses in the solid rotor get rather high. The modeling and the prediction of eddy-current

  18. Tower Winds - Cape Kennedy

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Digitized data taken from Wind Gust Charts. Record contains hourly wind directions and speed with a peak wind recorded at the end of each day. Sorted by: station,...

  19. Transport of contaminants by Arctic sea ice and surface ocean currents

    International Nuclear Information System (INIS)

    Pfirman, S.

    1995-01-01

    Sea ice and ocean currents transport contaminants in the Arctic from source areas on the shelves, to biologically active regions often more than a thousand kilometers away. Coastal regions along the Siberian margin are polluted by discharges of agricultural, industrial and military wastes in river runoff, from atmospheric deposition and ocean dumping. The Kara Sea is of particular concern because of deliberate dumping of radioactive waste, as well as the large input of polluted river water. Contaminants are incorporated in ice during suspension freezing on the shelves, and by atmospheric deposition during drift. Ice releases its contaminant load through brine drainage, surface runoff of snow and meltwater, and when the floe disintegrates. The marginal ice zone, a region of intense biological activity, may also be the site of major contaminant release. Potentially contaminated ice from the Kara Sea is likely to influence the marginal ice zones of the Barents and Greenland seas. From studies conducted to date it appears that sea ice from the Kara Sea does not typically enter the Beaufort Gyre, and thus is unlikely to affect the northern Canadian and Alaskan margins

  20. Extreme bottom velocities induced by wind wave and currents in the Gulf of Gdańsk

    Science.gov (United States)

    Cieślikiewicz, Witold; Dudkowska, Aleksandra; Gic-Grusza, Gabriela; Jędrasik, Jan

    2017-11-01

    The principal goal of this study is to get some preliminary insights about the intensity of water movement generated by wind waves, and due to the currents in the bottom waters of Gulf of Gdańsk, during severe storms. The Gulf of Gdańsk is located in the southern Baltic Sea. This paper presents the results of analysis of wave and current-induced velocities during extreme wind conditions, which are determined based on long-term historical records. The bottom velocity fields originated from wind wave and wind currents, during analysed extreme wind events, are computed independently of each other. The long-term wind wave parameters for the Baltic Sea region are derived from the 44-year hindcast wave database generated in the framework of the project HIPOCAS funded by the European Union. The output from the numerical wave model WAM provides the boundary conditions for the model SWAN operating in high-resolution grid covering the area of the Gulf of Gdańsk. Wind current velocities are calculated with the M3D hydrodynamic model developed in the Institute of Oceanography of the University of Gdańsk based on the POM model. The three dimensional current fields together with trajectories of particle tracers spreading out of bottom boundary layer are modelled, and the calculated fields of bottom velocities are presented in the form of 2D maps. During northerly winds, causing in the Gulf of Gdańsk extreme waves and most significant wind-driven circulation, the wave-induced bottom velocities are greater than velocities due to currents. The current velocities in the bottom layer appeared to be smaller by an order of magnitude than the wave-induced bottom orbital velocities. Namely, during most severe northerly storms analysed, current bottom velocities ranged about 0.1-0.15 m/s, while the root mean square of wave-induced near-seabed velocities reached maximum values of up to 1.4 m/s in the southern part of Gulf of Gdańsk.

  1. A fully implicit formulation of a layered wind-driven ocean model with outcropping

    Science.gov (United States)

    Primeau, F. W.; Newman, D.

    2004-12-01

    We have implemented an implicit solver for a layered formulation of the primitive equations. The advantage of the layered formulation is that there is no spurious diapycnal diffusivity due to the numerical representation of the advective terms. The numerical scheme is based on Hsu and Arakawa (1990) and allows isopycnic layers to outcrop at the surface. This makes it possible for us to explore solutions where the deeper layers are forced directly by the wind along their surface outcrop. The stationary solutions of the model are solved using an arc-length continuation approach based on Newton's method. Here we report some preliminary results about the bifurcations and stability of the ventilated thermocline as a function of the eddy-viscosity.

  2. Feasibility of Tidal and Ocean Current Energy in False Pass, Aleutian Islands, Alaska final report

    Energy Technology Data Exchange (ETDEWEB)

    Wright, Bruce Albert [Aleutian Pribilof Islands Association, Inc., Anchorage, AK (United States)

    2014-05-07

    The Aleutian Pribilof Islands Association was awarded a U.S. Department of Energy Tribal Energy Program grant (DE-EE0005624) for the Feasibility of Tidal and Ocean Current Energy in False Pass, Aleutian Islands, Alaska (Project). The goal of the Project was to perform a feasibility study to determine if a tidal energy project would be a viable means to generate electricity and heat to meet long-term fossil fuel use reduction goals, specifically to produce at least 30% of the electrical and heating needs of the tribally-owned buildings in False Pass. The Project Team included the Aleut Region organizations comprised of the Aleutian Pribilof Island Association (APIA), and Aleutian Pribilof Island Community Development Association (APICDA); the University of Alaska Anchorage, ORPC Alaska a wholly-owned subsidiary of Ocean Renewable Power Company (ORPC), City of False Pass, Benthic GeoScience, and the National Renewable Energy Laboratory (NREL). The following Project objectives were completed: collected existing bathymetric, tidal, and ocean current data to develop a basic model of current circulation at False Pass, measured current velocities at two sites for a full lunar cycle to establish the viability of the current resource, collected data on transmission infrastructure, electrical loads, and electrical generation at False Pass, performed economic analysis based on current costs of energy and amount of energy anticipated from and costs associated with the tidal energy project conceptual design and scoped environmental issues. Utilizing circulation modeling, the Project Team identified two target sites with strong potential for robust tidal energy resources in Isanotski Strait and another nearer the City of False Pass. In addition, the Project Team completed a survey of the electrical infrastructure, which identified likely sites of interconnection and clarified required transmission distances from the tidal energy resources. Based on resource and electrical data

  3. Power Management Based Current Control Technique for Photovoltaic-Battery Assisted Wind-Hydro Hybrid System

    Science.gov (United States)

    Ram Prabhakar, J.; Ragavan, K.

    2013-07-01

    This article proposes new power management based current control strategy for integrated wind-solar-hydro system equipped with battery storage mechanism. In this control technique, an indirect estimation of load current is done, through energy balance model, DC-link voltage control and droop control. This system features simpler energy management strategy and necessitates few power electronic converters, thereby minimizing the cost of the system. The generation-demand (G-D) management diagram is formulated based on the stochastic weather conditions and demand, which would likely moderate the gap between both. The features of management strategy deploying energy balance model include (1) regulating DC-link voltage within specified tolerances, (2) isolated operation without relying on external electric power transmission network, (3) indirect current control of hydro turbine driven induction generator and (4) seamless transition between grid-connected and off-grid operation modes. Furthermore, structuring of the hybrid system with appropriate selection of control variables enables power sharing among each energy conversion systems and battery storage mechanism. By addressing these intricacies, it is viable to regulate the frequency and voltage of the remote network at load end. The performance of the proposed composite scheme is demonstrated through time-domain simulation in MATLAB/Simulink environment.

  4. Counterintuitive effects of Global Warming-induced wind patterns on primary production in the Northern Humboldt Current System.

    Science.gov (United States)

    Mogollón, Rodrigo; Calil, Paulo H R

    2018-04-14

    It has been hypothesized that global warming will strengthen upwelling-favorable winds in the Northern Humboldt Current System (NHCS) as a consequence of the increase of the land-sea thermal gradient along the Peruvian coast. The effect of strengthened winds in this region is assessed with the use of a coupled physical-biogeochemical model forced with projected and climatological winds. Strengthened winds induce an increase in primary production of 2% per latitudinal degree from 9.5°S to 5°S. In some important coastal upwelling sites primary production is reduced. This is due to a complex balance between nutrient availability, nutrient use efficiency, as well as eddy and wind-driven factors. Mesoscale activity induces a net offshore transport of inorganic nutrients, thus reducing primary production in the coastal upwelling region. Wind mixing, in general disadvantageous for primary producers, leads to shorter residence times in the southern and central coastal zones. Overall, instead of a proportional enhancement in primary production due to increased winds, the NHCS becomes only 5% more productive (+ 5 mol C m -2 yr -1 ), 10% less limited by nutrients and 15% less efficient due to eddy-driven effects. It is found that regions with a initial strong nutrient limitation are more efficient in terms of nutrient assimilation which makes them more resilient in face of the acceleration of the upwelling circulation. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  5. Ocean Biogeochemistry in the California Current System 2007-2010 L4 Monthly

    Data.gov (United States)

    National Aeronautics and Space Administration — A coupled physical-biogeochemical ocean model (the MITgcm with BLING biogeochemistry) is a least squares fit to all available ocean observations in the region of the...

  6. Shelf sea tidal currents and mixing fronts determined from ocean glider observations

    Science.gov (United States)

    Sheehan, Peter M. F.; Berx, Barbara; Gallego, Alejandro; Hall, Rob A.; Heywood, Karen J.; Hughes, Sarah L.; Queste, Bastien Y.

    2018-03-01

    Tides and tidal mixing fronts are of fundamental importance to understanding shelf sea dynamics and ecosystems. Ocean gliders enable the observation of fronts and tide-dominated flows at high resolution. We use dive-average currents from a 2-month (12 October-2 December 2013) glider deployment along a zonal hydrographic section in the north-western North Sea to accurately determine M2 and S2 tidal velocities. The results of the glider-based method agree well with tidal velocities measured by current meters and with velocities extracted from the TPXO tide model. The method enhances the utility of gliders as an ocean-observing platform, particularly in regions where tide models are known to be limited. We then use the glider-derived tidal velocities to investigate tidal controls on the location of a front repeatedly observed by the glider. The front moves offshore at a rate of 0.51 km day-1. During the first part of the deployment (from mid-October until mid-November), results of a one-dimensional model suggest that the balance between surface heat fluxes and tidal stirring is the primary control on frontal location: as heat is lost to the atmosphere, full-depth mixing is able to occur in progressively deeper water. In the latter half of the deployment (mid-November to early December), a front controlled solely by heat fluxes and tidal stirring is not predicted to exist, yet a front persists in the observations. We analyse hydrographic observations collected by the glider to attribute the persistence of the front to the boundary between different water masses, in particular to the presence of cold, saline, Atlantic-origin water in the deeper portion of the section. We combine these results to propose that the front is a hybrid front: one controlled in summer by the local balance between heat fluxes and mixing and which in winter exists as the boundary between water masses advected to the north-western North Sea from diverse source regions. The glider observations

  7. Shelf sea tidal currents and mixing fronts determined from ocean glider observations

    Directory of Open Access Journals (Sweden)

    P. M. F. Sheehan

    2018-03-01

    Full Text Available Tides and tidal mixing fronts are of fundamental importance to understanding shelf sea dynamics and ecosystems. Ocean gliders enable the observation of fronts and tide-dominated flows at high resolution. We use dive-average currents from a 2-month (12 October–2 December 2013 glider deployment along a zonal hydrographic section in the north-western North Sea to accurately determine M2 and S2 tidal velocities. The results of the glider-based method agree well with tidal velocities measured by current meters and with velocities extracted from the TPXO tide model. The method enhances the utility of gliders as an ocean-observing platform, particularly in regions where tide models are known to be limited. We then use the glider-derived tidal velocities to investigate tidal controls on the location of a front repeatedly observed by the glider. The front moves offshore at a rate of 0.51 km day−1. During the first part of the deployment (from mid-October until mid-November, results of a one-dimensional model suggest that the balance between surface heat fluxes and tidal stirring is the primary control on frontal location: as heat is lost to the atmosphere, full-depth mixing is able to occur in progressively deeper water. In the latter half of the deployment (mid-November to early December, a front controlled solely by heat fluxes and tidal stirring is not predicted to exist, yet a front persists in the observations. We analyse hydrographic observations collected by the glider to attribute the persistence of the front to the boundary between different water masses, in particular to the presence of cold, saline, Atlantic-origin water in the deeper portion of the section. We combine these results to propose that the front is a hybrid front: one controlled in summer by the local balance between heat fluxes and mixing and which in winter exists as the boundary between water masses advected to the north-western North Sea from diverse source

  8. New Observations of C-band Brightness Temperatures and Ocean Surface Wind Speed and Rain Rate From the Hurricane Imaging Radiometer (HIRAD)

    Science.gov (United States)

    Miller, Timothy L.; James, M. W.; Roberts, J. B.; Buckley, C. D.; Biswas, S.; May, C.; Ruf, C. S.; Uhlhorn, E. W.; Atlas, R.; Black, P.; hide

    2012-01-01

    HIRAD flew on the WB-57 during NASA's GRIP (Genesis and Rapid Intensification Processes) campaign in August September of 2010. HIRAD is a new C-band radiometer using a synthetic thinned array radiometer (STAR) technology to obtain cross-track resolution of approximately 3 degrees, out to approximately 60 degrees to each side of nadir. By obtaining measurements of emissions at 4, 5, 6, and 6.6 GHz, observations of ocean surface wind speed and rain rate can be retrieved. This technique has been used for many years by precursor instruments, including the Stepped Frequency Microwave Radiometer (SFMR), which has been flying on the NOAA and USAF hurricane reconnaissance aircraft for several years to obtain observations within a single footprint at nadir angle. Results from the flights during the GRIP campaign will be shown, including images of brightness temperatures, wind speed, and rain rate. Comparisons will be made with observations from other instruments on the GRIP campaign, for which HIRAD observations are either directly comparable or are complementary. Features such as storm eye and eyewall, location of storm wind and rain maxima, and indications of dynamical features such as the merging of a weaker outer wind/rain maximum with the main vortex may be seen in the data. Potential impacts on operational ocean surface wind analyses and on numerical weather forecasts will also be discussed.

  9. Total kinetic energy in four global eddying ocean circulation models and over 5000 current meter records

    KAUST Repository

    Scott, Robert B.

    2010-01-01

    We compare the total kinetic energy (TKE) in four global eddying ocean circulation simulations with a global dataset of over 5000, quality controlled, moored current meter records. At individual mooring sites, there was considerable scatter between models and observations that was greater than estimated statistical uncertainty. Averaging over all current meter records in various depth ranges, all four models had mean TKE within a factor of two of observations above 3500. m, and within a factor of three below 3500. m. With the exception of observations between 20 and 100. m, the models tended to straddle the observations. However, individual models had clear biases. The free running (no data assimilation) model biases were largest below 2000. m. Idealized simulations revealed that the parameterized bottom boundary layer tidal currents were not likely the source of the problem, but that reducing quadratic bottom drag coefficient may improve the fit with deep observations. Data assimilation clearly improved the model-observation comparison, especially below 2000. m, despite assimilated data existing mostly above this depth and only south of 47°N. Different diagnostics revealed different aspects of the comparison, though in general the models appeared to be in an eddying-regime with TKE that compared reasonably well with observations. © 2010 Elsevier Ltd.

  10. Fixed speed wind farm operation improvement using current-source converter based UPQC

    International Nuclear Information System (INIS)

    Ajami, Ali; Armaghan, Mehdi

    2012-01-01

    Highlights: ► Reactive power and voltage sag are compensated during grid side fault. ► Nonlinear model of UPQC is modified to a linear model. ► Using the CSI in proposed UPQC offers a number of distinct advantages. ► Pitch angle controller is used to obtain nominal power at high wind speeds. ► Optimal control method (LQR) is used to determine the optimal state feedback gains. - Abstract: In this paper, a current-source converter based unified power quality conditioner (UPQC) is used for the flexible integration of pitch controlled fixed speed wind generator (FSWG) to IEEE 13 node test feeder. During the normal operation, shunt compensator (SHUC) of the UPQC maintains a unity power factor condition at the Point of Common Coupling (PCC) and when a voltage sag occurs due to grid side fault the series compensator (SERC) of the UPQC injects appropriate deficit voltage to prevent disconnecting of the FSWG and the SHUC of the UPQC provides additional reactive power in fault during. The pitch angle is controlled in order to limit the generator output power to its nominal value for high wind speeds. The nonlinear model of the shunt compensator of the UPQC is modified to a linear model. The modeling technique is not based on the linearization of a set of nonlinear equations around an operating point. Instead, the power balance equation and a nonlinear input transformation are used to derive a linear model independent of the operating point. This model acts as the basis for the design of a decoupled state-feedback controller. The optimal control method linear quadratic regulator (LQR) is used to determine the optimal state-feedback gain matrix. The proposed control approach becomes a robust strategy that is able to keep regulation and stability even under extreme load power factor variations. The In-phase voltage injection method is used for the series compensator of the UPQC. The simulation results carried out by MATLAB/SIMULINK software show the performance of the

  11. Direct Torque Control in presence of Current sensor failure in Variable Speed Wind System: Effect analysis, detection and control reconfiguration

    Directory of Open Access Journals (Sweden)

    A. J. Arbi

    2008-03-01

    Full Text Available This paper presents a study of current sensor failure in a Direct Torque Control applied to a Double Fed Induction Generator based Variable Speed Wind System. The effect of scaling and offset current sensor errors is discussed through sensibility analysis. A control reconfiguration is then proposed to remedy this sensor failure. Simulation results emphasize the good performances of the proposed current sensor fault tolerant control

  12. 3D Numerical Simulation of the Wave and Current Loads on a Truss Foundation of the Offshore Wind Turbine During the Extreme Typhoon Event

    Science.gov (United States)

    Lin, C. W.; Wu, T. R.; Chuang, M. H.; Tsai, Y. L.

    2015-12-01

    The wind in Taiwan Strait is strong and stable which offers an opportunity to build offshore wind farms. However, frequently visited typhoons and strong ocean current require more attentions on the wave force and local scour around the foundation of the turbine piles. In this paper, we introduce an in-house, multi-phase CFD model, Splash3D, for solving the flow field with breaking wave, strong turbulent, and scour phenomena. Splash3D solves Navier-Stokes Equation with Large-Eddy Simulation (LES) for the fluid domain, and uses volume of fluid (VOF) with piecewise linear interface reconstruction (PLIC) method to describe the break free-surface. The waves were generated inside the computational domain by internal wave maker with a mass-source function. This function is designed to adequately simulate the wave condition under observed extreme events based on JONSWAP spectrum and dispersion relationship. Dirichlet velocity boundary condition is assigned at the upper stream boundary to induce the ocean current. At the downstream face, the sponge-layer method combined with pressure Dirichlet boundary condition is specified for dissipating waves and conducting current out of the domain. Numerical pressure gauges are uniformly set on the structure surface to obtain the force distribution on the structure. As for the local scour around the foundation, we developed Discontinuous Bi-viscous Model (DBM) for the development of the scour hole. Model validations were presented as well. The force distribution under observed irregular wave condition was extracted by the irregular-surface force extraction (ISFE) method, which provides a fast and elegant way to integrate the force acting on the surface of irregular structure. From the Simulation results, we found that the total force is mainly induced by the impinging waves, and the force from the ocean current is about 2 order of magnitude smaller than the wave force. We also found the dynamic pressure, wave height, and the

  13. An Initial Evaluation of Siting Considerations on Current and Future Wind Deployment

    Energy Technology Data Exchange (ETDEWEB)

    Tegen, Suzanne [National Renewable Energy Lab. (NREL), Golden, CO (United States); Lantz, Eric [National Renewable Energy Lab. (NREL), Golden, CO (United States); Mai, Trieu [National Renewable Energy Lab. (NREL), Golden, CO (United States); Heimiller, Donna [National Renewable Energy Lab. (NREL), Golden, CO (United States); Hand, Maureen [National Renewable Energy Lab. (NREL), Golden, CO (United States); Ibanez, Eduardo [GE Energy Consulting, Denver, CO (United States)

    2016-07-01

    This report provides a deeper understanding of the wind project development process, from desktop studies to a successful project in the ground. It examines three siting consideration categories that wind project sponsors must include in the development process: wildlife (species that live in, near, or migrate through the area where wind development is possible), radar (wind turbines can cause interference with radar signals), and public engagement (representing communities and stakeholders who live near wind power projects). The research shows that although this country's abundant wind resource provides numerous options for addressing siting considerations, actually siting individual projects is becoming more difficult because of regulatory and other uncertainties. Model results are based on the premise that developers will be able to site, permit, and build successful projects, which is not always the case in reality.

  14. Expression of the Middle-Late Miocene "Carbonate Crash" and "Biogenic Bloom" in the Benguela Current Upwelling Area of the South Atlantic Ocean

    Science.gov (United States)

    Diester-Haass, L.; Meyers, P. A.; Bauman, S. C.

    2001-05-01

    The middle-late Miocene "carbonate crash" - several episodes with significant drops in concentrations and accumulation rates of CaCO3 - occurred between 13 and 9 Ma in the equatorial Pacific and Indian Oceans and the Carribean Sea (Lyle et al., 1995; Roth et al., 2000). This event is followed by a "biogenic bloom" - a strong increase in biogenous production that has been described in the equatorial Pacific and Indian Oceans. In order to explain these two events, the questions of whether they are confined to tropical upwelling areas, whether they also occur in coastal upwelling areas, or whether they are global phenomena must be answered. We have explored the expression of these events during the evolution of the Benguela Current upwelling system. Sediment sequences from ODP Sites 1085 and 1087 record several drops in carbonate concentrations in the middle and early late Miocene that culminate in a major depression at 9.5-9.0 Ma and that are synchronous with the "carbonate crash" in the equatorial Pacific (Lyle et al., 1995). Climatic changes in SW Africa, reflected by an increase in delivery terrigenous sediment components and by a larger proportion of kaolinite, and oceanic changes, indicated by an expansion of the oxygen minimum zone, accompany this event. Oxygen depletion starts during early carbonate depressions and has a maximum during the major CaCO3 depression. Marine biological productivity, as reconstructed from concentrations of organic carbon and benthic foraminiferal accumulation rates, is at a minimum in the middle-early late Miocene. However, it increases 3-6 fold at 6.5 Ma, a shift that is synchronous with the "biogenic bloom" in the equatorial Pacific Ocean (Farrell et al., 1995). We attribute this important paleoceanographic change to a strengthening of latitudinal temperature gradients and corresponding vertical mixing by zonal winds during the onset of North Atlantic Deep Water flow, which led to more vigorous deep ventilation and emergence of

  15. RECONSTRUCTING THE SOLAR WIND FROM ITS EARLY HISTORY TO CURRENT EPOCH

    International Nuclear Information System (INIS)

    Airapetian, Vladimir S.; Usmanov, Arcadi V.

    2016-01-01

    Stellar winds from active solar-type stars can play a crucial role in removal of stellar angular momentum and erosion of planetary atmospheres. However, major wind properties except for mass-loss rates cannot be directly derived from observations. We employed a three-dimensional magnetohydrodynamic Alfvén wave driven solar wind model, ALF3D, to reconstruct the solar wind parameters including the mass-loss rate, terminal velocity, and wind temperature at 0.7, 2, and 4.65 Gyr. Our model treats the wind thermal electrons, protons, and pickup protons as separate fluids and incorporates turbulence transport, eddy viscosity, turbulent resistivity, and turbulent heating to properly describe proton and electron temperatures of the solar wind. To study the evolution of the solar wind, we specified three input model parameters, the plasma density, Alfvén wave amplitude, and the strength of the dipole magnetic field at the wind base for each of three solar wind evolution models that are consistent with observational constrains. Our model results show that the velocity of the paleo solar wind was twice as fast, ∼50 times denser and 2 times hotter at 1 AU in the Sun's early history at 0.7 Gyr. The theoretical calculations of mass-loss rate appear to be in agreement with the empirically derived values for stars of various ages. These results can provide realistic constraints for wind dynamic pressures on magnetospheres of (exo)planets around the young Sun and other active stars, which is crucial in realistic assessment of the Joule heating of their ionospheres and corresponding effects of atmospheric erosion

  16. Conductivity data from moored current meter casts in the North Pacific Ocean from 1979-04-23 to 1981-10-01 (NODC Accession 8200163)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Conductivity data were collected using moored current meter casts in the North Pacific Ocean from April 23, 1979 to October 1, 1981. Data were submitted by...

  17. Conductivity data from moored current meter casts in the North Pacific Ocean from 1980-08-05 to 1981-08-01 (NODC Accession 8300053)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Conductivity data were collected using moored current meter casts in the North Pacific Ocean from August 5, 1980 to August 1, 1981. Data were submitted by University...

  18. Temperature and conductivity data from moored current meter casts in the North Pacific Ocean from 1978-10-18 to 1980-08-01 (NODC Accession 8200188)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature and conductivity data were collected using moored current meter casts in the North Pacific Ocean from October 18, 1978 to August 1, 1980. Data were...

  19. Current issues concerning the representativeness and utility of cloud drift winds in mesoscale meteorology

    Science.gov (United States)

    Koch, Steven E.

    1985-01-01

    High-resolution cloud motion wind (CMW) data sets obtained from geostationary satellites for approximately the past decade have been used for the purpose of estimating mesoscale wind fields in various research studies. Yet there remains much controversy surrounding the proper interpretation and use of the resultant wind vector and kinematic fields. This paper is concerned with: (1) how representative are cloud draft winds of actual ambient air motions; and (2) what is the degree of practical usefulness of CMW fields for both mesoscale analysis and as input to numerical weather prediction models.

  20. Presal36: a high resolution ocean current model for Brazilian pre-salt area: implementation and validation results

    Energy Technology Data Exchange (ETDEWEB)

    Schoellkopf, Jacques P. [Advanced Subsea do Brasil Ltda., Rio de Janeiro, RJ (Brazil)

    2012-07-01

    The PRESAL 36 JIP is a project for the development of a powerful Ocean Current Model of 1/36 of a degree resolution, nested in an existing Global Ocean global Model, Mercator PSY4 (1/12-a-degree resolution ), with tide corrections, improved bathymetry accuracy and high frequency atmospheric forcing (every 3 hours). The simulation outputs will be the 3 dimensional structure of the velocity fields (u,v,w) at 50 vertical levels over the water column, including geostrophic, Ekman and tidal currents, together with Temperature, Salinity and sea surface height at a sub-mesoscale spatial resolution. Simulations will run in hindcast, nowcast and forecast modes, with a temporal resolution of 3 hours . This Ocean current model will allow to perform detailed statistical studies on various areas using conditions analysed using hindcast mode, short term operational condition prediction for various surface and sub sea operations using realtime and Forecast modes. The paper presents a publication of significant results of the project, in term of pre-sal zoomed model implementation, and high resolution model validation. It demonstrate the capability to properly describe ocean current phenomenon at beyond mesoscale frontier. This project demonstrate the feasibility of obtaining accurate information for engineering studies and operational conditions, based on a 'zoom technique' starting from global ocean models. (author)

  1. Coordination between Fault-Ride-Through Capability and Over-current Protection of DFIG Generators for Wind Farms

    DEFF Research Database (Denmark)

    Bak-Jensen, Birgitte; Kawady, T.A.; Abdel-Rahman, Mansour Hassan

    2010-01-01

    Fault Ride-Through (FRT) capabilities set up according to the grid codes may affect the performance of related protective elements during fault periods. Therefore, in this paper the coordination between the FRT capability and over-current protection of DFIG Wind Generators in MV networks...... is investigated. Simulation test cases using MATLAB-Simulink are implemented on a 365-MW wind farm in AL-Zaafarana, Egypt. The simulation results show the influence of the FRT capability on the protective relaying coordination in wind farms, showing that the FRT may work in situations where is were expected...... not to work, and then disabling the over-current protection, which should have worked in this situation....

  2. Effects of electrode gap and electric current on chlorine generation of electrolyzed deep ocean water.

    Science.gov (United States)

    Hsu, Guoo-Shyng Wang; Hsu, Shun-Yao

    2018-04-01

    Electrolyzed water is a sustainable disinfectant, which can comply with food safety regulations and is environmental friendly. A two-factor central composite design was adopted for studying the effects of electrode gap and electric current on chlorine generation efficiency of electrolyzed deep ocean water. Deep ocean water was electrolyzed in a glass electrolyzing cell equipped with platinum-plated titanium anode and cathode in a constant-current operation mode. Results showed that current density, chlorine concentration, and electrolyte temperature increased with electric current, while electric efficiency decreased with electric current and electrode gap. An electrode gap of less than 11.7 mm, and a low electric current appeared to be a more energy efficient design and operation condition for the electrolysis system. Copyright © 2017. Published by Elsevier B.V.

  3. Current meter and marine toxic substances data from moored current meter casts and other instruments in the North Pacific Ocean as part of the Deep Ocean Mining and Environmental Study (DOMES) project, 1975-08-29 to 1977-12-01 (NODC Accession 7800741)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter and marine toxic substances data were collected using moored current meter casts and other instruments in the North Pacific Ocean from August 29, 1975...

  4. Simulation Tool for GNSS Ocean Surface Reflections

    OpenAIRE

    Høeg, Per; von Benzon, Hans-Henrik; Durgonics, Tibor

    2015-01-01

    GNSS coherent and incoherent reflected signals have the potential of deriving large scale parameters of ocean surfaces, as barotropic variability, eddy currents and fronts, Rossby waves, coastal upwelling, mean ocean surfaceheights, and patterns of the general ocean circulation. In the reflection zone the measurements may deriveparameters as sea surface roughness, winds, waves, heights and tilts from the spectral measurements. Previous measurements from the top of mountains and airplanes have...

  5. Relationships between ERTS radiances and gradients across ocean fronts. [image enhancement of Loop Current in Gulf of Mexico

    Science.gov (United States)

    Maul, G. A.; Gordon, H. R.

    1974-01-01

    A time series of the Loop Current in the Gulf of Mexico, covering an annual cycle of growth, spreading, and decay, has been obtained in synchronization with ERTS. Computer enhanced images, which are necessary to extract useful oceanic information, show that the current can be observed either by color or sea state effects associated with the cyclonic boundary. The color effect relates to the spectral variations in the optical properties of the water and its suspended particles, and is studied by radiative transfer theory. Significant oceanic parameters identified are: the probability of forward scattering, and the ratio of scattering to total attenuation.

  6. The Solar Wind: Our Current Understanding and How We Got Here ...

    Indian Academy of Sciences (India)

    addition (rS is the solar radius). 3. The wave-driven wind. The next major advance was the discovery (Belcher & Davis 1971) of the ubiquitous presence of Alfvén waves in the solar wind. Most of the wave power resides at long periods, of the order of hours. The waves predominantly propagate away from the Sun, especially ...

  7. The Use of MTM-SVD Technique to Explore the Joint Spatiotemporal Modes of Wind and Sea Surface Variability in the North Indian Ocean during 1993–2005

    Directory of Open Access Journals (Sweden)

    Thaned Rojsiraphisal

    2009-01-01

    Full Text Available Sea surface height (SSH and sea surface temperature (SST in the North Indian Ocean are affected predominantly by the seasonally reversing monsoons and in turn feed back on monsoon variability. In this study, a set of data generated from a data-assimilative ocean model is used to examine coherent spatiotemporal modes of variability of winds and surface parameters using a frequency domain technique, Multiple Taper Method with Singular Value Decomposition (MTM-SVD. The analysis shows significant variability at annual and semiannual frequencies in these fields individually and jointly. The joint variability of winds and SSH is significant at interannual (2-3 years timescale related to the ENSO mode—with a “/dipole/” like spatial pattern. Joint variability with SST showed similar but somewhat weaker behavior. Winds appear to be the driver of variability in both SSH and SST at these frequency bands. This offers prospects for long-lead projections of the North Indian Ocean climate.

  8. Prognostics and Health Management of Wind Turbines -- Current Status and Future Opportunities

    Energy Technology Data Exchange (ETDEWEB)

    Sheng, Shuangwen

    2017-04-28

    The global wind industry has seen tremendous growth during the past two decades. However, the industry is challenged by premature component failures, which lead to increased turbine downtime and subsequently, cost of energy for wind power. To mitigate the impacts from these failures, the wind industry has been exploring various areas for improvements ranging from product design, new materials or lubricants, to operation and maintenance (O&M) practices. Condition-based maintenance or prognostics and health management (PHM) has been explored as one enabling technology for improving O&M practices. This chapter provides a brief overview of wind turbine PHM with a focus on operational data mining and condition monitoring of drivetrains. Some future research and development opportunities in wind turbine PHM are also briefly discussed.

  9. Wind Energy Finance in the United States: Current Practice and Opportunities

    Energy Technology Data Exchange (ETDEWEB)

    Schwabe, Paul D. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Feldman, David J. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Settle, Donald E. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Fields, Jason [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2017-08-08

    In the United States, investment in wind energy has averaged nearly $13.6 billion annually since 2006 with more than $140 billion invested cumulatively over that period (BNEF 2017). This sizable investment activity demonstrates the persistent appeal of wind energy and its increasing role in the U.S electricity generation portfolio. Despite its steady investment levels over the last decade, some investors still consider wind energy as a specialized asset class. Limited familiarity with the asset class both limit the pool of potential investors and drive up costs for investors. This publication provides an overview of the wind project development process, capital sources and financing structures commonly used, and traditional and emerging procurement methods. It also provides a high-level demonstration of how financing rates impact a project's all-in cost of energy. The goal of the publication is to provide a representative and wide-ranging resource for the wind development and financing processes.

  10. Review on Available Information on Wind, Water Level, Current, Geology and Bathymetry in the DanWEC Area

    DEFF Research Database (Denmark)

    Margheritini, Lucia

    level, geology and bathymetry information at the DanWEC location. The present report has been prepared under the project No. 834101 “DanWEC Vaekstforum 2011”, task 3: “Collection and presentation of basic data about wind, current, water head, bathymetry and geology for the DanWEC site at the Port...

  11. Fluid-structure interaction simulation of floating structures interacting with complex, large-scale ocean waves and atmospheric turbulence with application to floating offshore wind turbines

    Science.gov (United States)

    Calderer, Antoni; Guo, Xin; Shen, Lian; Sotiropoulos, Fotis

    2018-02-01

    We develop a numerical method for simulating coupled interactions of complex floating structures with large-scale ocean waves and atmospheric turbulence. We employ an efficient large-scale model to develop offshore wind and wave environmental conditions, which are then incorporated into a high resolution two-phase flow solver with fluid-structure interaction (FSI). The large-scale wind-wave interaction model is based on a two-fluid dynamically-coupled approach that employs a high-order spectral method for simulating the water motion and a viscous solver with undulatory boundaries for the air motion. The two-phase flow FSI solver is based on the level set method and is capable of simulating the coupled dynamic interaction of arbitrarily complex bodies with airflow and waves. The large-scale wave field solver is coupled with the near-field FSI solver with a one-way coupling approach by feeding into the latter waves via a pressure-forcing method combined with the level set method. We validate the model for both simple wave trains and three-dimensional directional waves and compare the results with experimental and theoretical solutions. Finally, we demonstrate the capabilities of the new computational framework by carrying out large-eddy simulation of a floating offshore wind turbine interacting with realistic ocean wind and waves.

  12. A HPC “Cyber Wind Facility” Incorporating Fully-Coupled CFD/CSD for Turbine-Platform-Wake Interactions with the Atmosphere and Ocean

    Energy Technology Data Exchange (ETDEWEB)

    Brasseur, James G. [Univ. of Colorado, Boulder, CO (United States)

    2017-05-09

    The central aims of the DOE-supported “Cyber Wind Facility” project center on the recognition that wind turbines over land and ocean generate power from atmospheric winds that are inherently turbulent and strongly varying, both spatially over the rotor disk and in temporally as the rotating blades pass through atmospheric eddies embedded within the mean wind. The daytime unstable atmospheric boundary layer (ABL) is particularly variable in space time as solar heating generates buoyancy-driven motions that interact with strong mean shear in the ABL “surface layer,” the lowest 200 - 300 m where wind turbines reside in farms. With the “Cyber Wind Facility” (CWF) program we initiate a research and technology direction in which “cyber data” are generated from “computational experiments” within a “facility” akin to a wind tunnel, but with true space-time atmospheric turbulence that drive utility-scale wind turbines at full-scale Reynolds numbers. With DOE support we generated the key “modules” within a computational framework to create a first generation Cyber Wind Facility (CWF) for single wind turbines in the daytime ABL---both over land where the ABL globally unstable and over water with closer-to-neutral atmospheric conditions but with time response strongly affected by wave-induced forcing of the wind turbine platform (here a buoy configuration). The CWF program has significantly improved the accuracy of actuator line models, evaluated with the Cyber Wind Facility in full blade-boundary-layer-resolved mode. The application of the CWF made in this program showed the existence of important ramp-like response events that likely contribute to bearing fatigue failure on the main shaft and that the advanced ALM method developed here captures the primary nonsteady response characteristics. Long-time analysis uncovered distinctive key dynamics that explain primary mechanisms that underlie potentially deleterious load transients. We also showed

  13. Analysis and Suppression of Zero Sequence Circulating Current in Open Winding PMSM Drives With Common DC Bus

    OpenAIRE

    Zhan, H.; Zhu, Z.Q.; Odavic, M.

    2017-01-01

    In this paper, the zero sequence circulating current in open winding permanent magnet synchronous machine (OW-PMSM) drives with common dc bus is systematically analyzed for the first time. It is revealed that the zero sequence circulating current is affected by zero sequence back-electromotive force, cross coupling voltages in zero sequence from the machine side, pulse-width modulation induced zero sequence voltage, and inverter nonlinearity from the inverter side. Particularly, the influence...

  14. Dynamic Stability Enhancement and Power Flow Control of a Hybrid Wind and Marine-Current Farm Using SMES

    DEFF Research Database (Denmark)

    Wang, Li; Chen, Shiang-Shong; Lee, Wei-Jen

    2009-01-01

    This paper presents a control scheme based on a superconducting magnetic energy storage (SMES) unit to achieve both power flow control and damping enhancement of a novel hybrid wind and marine-current farm (MCF) connected to a large power grid. The performance of the studied wind farm (WF......) is simulated by an equivalent 80-MW induction generator (IG) while an equivalent 60-MW IG is employed to simulate the characteristics of theMCF. A damping controller for the SMES unit is designed by using modal control theory to contribute effective damping characteristics to the studied combined WF and MCF...

  15. Southern Ocean overturning across streamlines in an eddying simulation of the Antarctic Circumpolar Current

    Directory of Open Access Journals (Sweden)

    A. M. Treguier

    2007-12-01

    Full Text Available An eddying global model is used to study the characteristics of the Antarctic Circumpolar Current (ACC in a streamline-following framework. Previous model-based estimates of the meridional circulation were calculated using zonal averages: this method leads to a counter-intuitive poleward circulation of the less dense waters, and underestimates the eddy effects. We show that on the contrary, the upper ocean circulation across streamlines agrees with the theoretical view: an equatorward mean flow partially cancelled by a poleward eddy mass flux. Two model simulations, in which the buoyancy forcing above the ACC changes from positive to negative, suggest that the relationship between the residual meridional circulation and the surface buoyancy flux is not as straightforward as assumed by the simplest theoretical models: the sign of the residual circulation cannot be inferred from the surface buoyancy forcing only. Among the other processes that likely play a part in setting the meridional circulation, our model results emphasize the complex three-dimensional structure of the ACC (probably not well accounted for in streamline-averaged, two-dimensional models and the distinct role of temperature and salinity in the definition of the density field. Heat and salt transports by the time-mean flow are important even across time-mean streamlines. Heat and salt are balanced in the ACC, the model drift being small, but the nonlinearity of the equation of state cannot be ignored in the density balance.

  16. AMS Weather Studies and AMS Ocean Studies: Dynamic, College-Level Geoscience Courses Emphasizing Current Earth System Data

    Science.gov (United States)

    Brey, J. A.; Geer, I. W.; Moran, J. M.; Weinbeck, R. S.; Mills, E. W.; Blair, B. A.; Hopkins, E. J.; Kiley, T. P.; Ruwe, E. E.

    2008-12-01

    AMS Weather Studies and AMS Ocean Studies are introductory college-level courses developed by the American Meteorological Society, with NSF and NOAA support, for local offering at undergraduate institutions nationwide. The courses place students in a dynamic and highly motivational educational environment where they investigate the atmosphere and world ocean using real-world and real-time environmental data. Over 360 colleges throughout the United States have offered these courses in course environments ranging from traditional lecture/laboratory to completely online. AMS Diversity Projects aim to increase undergraduate student access to the geosciences through implementation of the courses at minority-serving institutions and training programs for MSI faculty. The AMS Weather Studies and AMS Ocean Studies course packages consist of a hard-cover, 15-chapter textbook, Investigations Manual with 30 lab-style activities, and course website containing weekly current weather and ocean investigations. Course instructors receive access to a faculty website and CD containing answer keys and course management system-compatible files, which allow full integration to a college's e-learning environment. The unique aspect of the courses is the focus on current Earth system data through weekly Current Weather Studies and Current Ocean Studies investigations written in real time and posted to the course website, as well as weekly news files and a daily weather summary for AMS Weather Studies. Students therefore study meteorology or oceanography as it happens, which creates a dynamic learning environment where student relate their experiences and observations to the course, and actively discuss the science with their instructor and classmates. With NSF support, AMS has held expenses-paid course implementation workshops for minority-serving institution faculty planning to offer AMS Weather Studies or AMS Ocean Studies. From May 2002-2007, AMS conducted week-long weather workshops

  17. Current meter and other data collected using current meter casts from R/V RESEARCHER and R/V CALANUS in the Atlantic and Pacific Ocean as part of the Eastern Pacific Ocean Circulation Study (EPOCS) and Subtropical Atlantic Current Study (STACS), 23 March 1983 - 19 November 1986 (NODC Accession 8700226)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter and other data were collected using current meter casts from R/V RESEARCHER and R/V CALANUS in the Atlantic and Pacific Ocean from March 23, 1983 to...

  18. A Study on Maximum Wind Power Penetration Limit in Island Power System Considering High-Voltage Direct Current Interconnections

    Directory of Open Access Journals (Sweden)

    Minhan Yoon

    2015-12-01

    Full Text Available The variability and uncontrollability of wind power increases the difficulty for a power system operator to implement a wind power system with a high penetration rate. These are more serious factors to consider in small and isolated power systems since the system has small operating reserves and inertia to secure frequency and voltage. Typically, this difficulty can be reduced by interconnection with another robust power system using a controllable transmission system such as a high-voltage direct current (HVDC system. However, the reliability and stability constraints of a power system has to be performed according to the HVDC system implementation. In this paper, the method for calculation of maximum wind power penetration in an island supplied by a HVDC power system is presented, and the operational strategy of a HVDC system is proposed to secure the power system reliability and stability. The case study is performed for the Jeju Island power system in the Korean smart grid demonstration area.

  19. Dynamic Stability Enhancement and Power Flow Control of a Hybrid Wind and Marine-Current Farm Using SMES

    DEFF Research Database (Denmark)

    Wang, Li; Chen, Shiang-Shong; Lee, Wei-Jen

    2009-01-01

    be concluded from the simulated results that the proposed SMES unit combined with the designed damping controller is very effective to stabilize the studied combined WF and MCF under various wind speeds. The inherent fluctuations of the injected active power and reactive power of the WF and MCF to the power......This paper presents a control scheme based on a superconducting magnetic energy storage (SMES) unit to achieve both power flow control and damping enhancement of a novel hybrid wind and marine-current farm (MCF) connected to a large power grid. The performance of the studied wind farm (WF...... under different operating conditions. A frequency-domain approach based on a linearized system model using eigen techniques and a time-domain scheme based on a nonlinear system model subject to disturbance conditions are both employed to validate the effectiveness of the proposed control scheme. It can...

  20. Horizontal-Plane Trajectory-Tracking Control of an Underactuated Unmanned Marine Vehicle in the Presence of Ocean Currents

    Directory of Open Access Journals (Sweden)

    Zaopeng Dong

    2016-05-01

    Full Text Available Based on an integral backstepping approach, a trajectory-tracking control algorithm is proposed for an underactuated unmanned marine vehicle (UMV sailing in the presence of ocean-current disturbance. Taking into consideration the UMV model's fore/aft asymmetry, a nonlinear three-degree-of-freedom (3DOF underactuated dynamic model is established for the horizontal plane. First, trajectory-tracking differences between controllers designed based on symmetric and asymmetric models of the UMV are discussed. In order to explicitly study the effect of ocean-current interference on the trajectory-tracking controller, the ocean current is integrated into the kinematic and dynamic models of the UMV. Detailed descriptions of distinct trajectory-tracking control performances in the presence of different ocean-current velocities and direction angles are presented. The well-known persistent exciting (PE condition is completely released in the designed trajectory-tracking controller. A mild integral item of trajectory tracking error is merged into the control law, and global stability analysis of the UMV system is carried out using Lyapunov theory and Barbalat's Lemma. Simulation experiments in the semi-physical simulation platform are implemented to confirm the effectiveness and superiority of the excogitated control algorithm.

  1. Observations of an early Agulhas current retroflection event in 2001: a temporary cessation of inter-ocean exchange south of Africa?

    CSIR Research Space (South Africa)

    Van Aken, HM

    2013-02-01

    Full Text Available The exchange of heat and salt between the South Indian Ocean and South Atlantic Ocean, at the southern terminus of the Agulhas current, forms a crucial link in the global ocean circulation. It has been surmised that upstream retroflections...

  2. Current and future plans for wind energy development on San Clemente Island, California

    Energy Technology Data Exchange (ETDEWEB)

    Hurley, P.J.F. [RLA Consulting, Inc., Bothell, WA (United States); Cable, S.B. [Naval Facilities Engineering Service Center, Port Hueneme, CA (United States)

    1996-12-31

    The Navy is considering possible ways to maximize the use of wind energy technology for power supply to their auxiliary landing field and other facilities on San Clemente Island. A summary of their past analysis and future considerations is presented. An analysis was performed regarding the technical and economic feasibility of installing and operating a sea-water pumped hydro/wind energy system to provide for all of the island`s electric power needs. Follow-on work to the feasibility study include wind resource monitoring as well as procurement and preliminary design activities for a first-phase wind-diesel installation. Future plans include the consideration of alternative siting arrangements and the introduction of on-island fresh water production. 3 refs., 4 figs.

  3. Inertial currents in the Indian Ocean derived from satellite tracked surface drifters

    Digital Repository Service at National Institute of Oceanography (India)

    Saji, P.K.; Shenoi, S.S.C.; Almeida, A; Rao, L.V.G.

    activity, either triggered by the passage of atmospheric disturbances or by the local fluctuations in the atmospheric pressure (winds), did not last for more than 4 to 5 intertial cycles. The observed intertial frequency exhibited a shift towards the red...

  4. The Dependence of the Strength and Thickness of Field-Aligned Currents on Solar Wind and Ionospheric Parameters

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Jay R. [PPPL; Wing, Simon [Johns Hopkins University

    2014-08-01

    Sheared plasma flows at the low-latitude boundary layer correlate well with early afternoon auroral arcs and eld-aligned currents [Sonnerup, 1980; Lundin and Evans, 1985]. We present a simple analytic model that relates solar wind and ionospheric parameters to the strength and thickness of field-aligned currents in a region of sheared velocity, such as the low latitude boundary layer. We compare the predictions of the model with DMSP observations and nd remarkably good scaling of the currents with solar wind and ionospheric parameters. The sheared boundary layer thickness is inferred to be around 3000km consistent with observational studies. The analytic model provides a simple way to organize data and to infer boundary layer structures from ionospheric data.

  5. Current scenario of the wind energy in Pakistan challenges and future perspectives: A case study

    Directory of Open Access Journals (Sweden)

    Mazhar H. Baloch

    2016-11-01

    Full Text Available Electricity plays an important role in the socioeconomic growth and social prosperity of any country. It is to be considered as the basic need for human development. Nowadays, low production of electricity is a serious problem in Pakistan, which directly restricts the development of the state. One-third of Pakistan’s population does not have any electricity in the rural areas and about 10–12 hours load shedding in urban areas and is quite common. Although, the state of Pakistan always shows a deficit in the conventional resources, but no progress was also being made in the renewable resources such as the wind and solar energy. Therefore, it is better to utilize these natural assets in order to fulfill the electricity supply the country. In this manuscript, our main objective is to study and outlooks the country energy profile situation vis-à-vis wind energy potential characteristics of the most important wind corridor in the southern part of the country. Pakistan has around 1100 kilometers (km coastal line for the wind energy potential, but in this manuscript, we have chosen one of the most suitable wind corridors of the southern part of the country. We also tried to prove theoretically that this wind zone is more favorable for country consumer demand. Moreover, future perspective and the major challenges during windmill implementation is also being discussed herein.

  6. Observations of C-Band Brightness Temperatures and Ocean Surface Wind Speed and Rain Rate from the Hurricane Imaging Radiometer (HIRAD) during GRIP and HS3

    Science.gov (United States)

    Miller, Timothy L.; James, M. W.; Roberts, J. B.; Jones, W. L.; Biswas, S.; Ruf, C. S.; Uhlhorn, E. W.; Atlas, R.; Black, P.; Albers, C.

    2013-01-01

    HIRAD flew on high-altitude aircraft over Earl and Karl during NASA s GRIP (Genesis and Rapid Intensification Processes) campaign in August - September of 2010, and at the time of this writing plans to fly over Atlantic tropical cyclones in September of 2012 as part of the Hurricane and Severe Storm Sentinel (HS3) mission. HIRAD is a new C-band radiometer using a synthetic thinned array radiometer (STAR) technology to obtain cross-track resolution of approximately 3 degrees, out to approximately 60 degrees to each side of nadir. By obtaining measurements of emissions at 4, 5, 6, and 6.6 GHz, observations of ocean surface wind speed and rain rate can be retrieved. This technique has been used for many years by precursor instruments, including the Stepped Frequency Microwave Radiometer (SFMR), which has been flying on the NOAA and USAF hurricane reconnaissance aircraft for several years to obtain observations within a single footprint at nadir angle. Results from the flights during the GRIP and HS3 campaigns will be shown, including images of brightness temperatures, wind speed, and rain rate. Comparisons will be made with observations from other instruments on the campaigns, for which HIRAD observations are either directly comparable or are complementary. Features such as storm eye and eye-wall, location of storm wind and rain maxima, and indications of dynamical features such as the merging of a weaker outer wind/rain maximum with the main vortex may be seen in the data. Potential impacts on operational ocean surface wind analyses and on numerical weather forecasts will also be discussed.

  7. Hurricane Imaging Radiometer (HIRAD) Observations of Brightness Temperatures and Ocean Surface Wind Speed and Rain Rate During NASA's GRIP and HS3 Campaigns

    Science.gov (United States)

    Miller, Timothy L.; James, M. W.; Roberts, J. B.; Jones, W. L.; Biswas, S.; Ruf, C. S.; Uhlhorn, E. W.; Atlas, R.; Black, P.; Albers, C.

    2012-01-01

    HIRAD flew on high-altitude aircraft over Earl and Karl during NASA s GRIP (Genesis and Rapid Intensification Processes) campaign in August - September of 2010, and plans to fly over Atlantic tropical cyclones in September of 2012 as part of the Hurricane and Severe Storm Sentinel (HS3) mission. HIRAD is a new C-band radiometer using a synthetic thinned array radiometer (STAR) technology to obtain spatial resolution of approximately 2 km, out to roughly 30 km each side of nadir. By obtaining measurements of emissions at 4, 5, 6, and 6.6 GHz, observations of ocean surface wind speed and rain rate can be retrieved. The physical retrieval technique has been used for many years by precursor instruments, including the Stepped Frequency Microwave Radiometer (SFMR), which has been flying on the NOAA and USAF hurricane reconnaissance aircraft for several years to obtain observations within a single footprint at nadir angle. Results from the flights during the GRIP and HS3 campaigns will be shown, including images of brightness temperatures, wind speed, and rain rate. Comparisons will be made with observations from other instruments on the campaigns, for which HIRAD observations are either directly comparable or are complementary. Features such as storm eye and eye-wall, location of storm wind and rain maxima, and indications of dynamical features such as the merging of a weaker outer wind/rain maximum with the main vortex may be seen in the data. Potential impacts on operational ocean surface wind analyses and on numerical weather forecasts will also be discussed.

  8. Calibration and Validation of High Frequency Radar for Ocean Surface Current Mapping

    National Research Council Canada - National Science Library

    Kim, Kyung

    2004-01-01

    High Frequency (HF) radar backscatter instruments are being developed and tested in the marine science and defense science communities for their abilities to sense surface parameters remotely in the coastal ocean over large areas...

  9. Ocean Surface Current Vectors from MODIS Terra/Aqua Sea Surface Temperature Image Pairs, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Satellites that record imagery of the same sea surface area, at times separated by a few hours, can be used to estimate ocean surface velocity fields based on the...

  10. Impact of equalizing currents on losses and torque ripples in electrical machines with fractional slot concentrated windings

    Science.gov (United States)

    Toporkov, D. M.; Vialcev, G. B.

    2017-10-01

    The implementation of parallel branches is a commonly used manufacturing method of the realizing of fractional slot concentrated windings in electrical machines. If the rotor eccentricity is enabled in a machine with parallel branches, the equalizing currents can arise. The simulation approach of the equalizing currents in parallel branches of an electrical machine winding based on magnetic field calculation by using Finite Elements Method is discussed in the paper. The high accuracy of the model is provided by the dynamic improvement of the inductances in the differential equation system describing a machine. The pre-computed table flux linkage functions are used for that. The functions are the dependences of the flux linkage of parallel branches on the branches currents and rotor position angle. The functions permit to calculate self-inductances and mutual inductances by partial derivative. The calculated results obtained for the electric machine specimen are presented. The results received show that the adverse combination of design solutions and the rotor eccentricity leads to a high value of the equalizing currents and windings heating. Additional torque ripples also arise. The additional ripples harmonic content is not similar to the cogging torque or ripples caused by the rotor eccentricity.

  11. Fault Ride Through Capability Enhancement of a Large-Scale PMSG Wind System with Bridge Type Fault Current Limiters

    Directory of Open Access Journals (Sweden)

    ALAM, M. S.

    2018-02-01

    Full Text Available In this paper, bridge type fault current limiter (BFCL is proposed as a potential solution to the fault problems of permanent magnet synchronous generator (PMSG based large-scale wind energy system. As PMSG wind system is more vulnerable to disturbances, it is essential to guarantee the stability during severe disturbances by enhancing the fault ride through capability. BFCL controller has been designed to insert resistance and inductance during the inception of system disturbances in order to limit fault current. Constant capacitor voltage has been maintained by the grid voltage source converter (GVSC controller while current extraction or injection has been achieved by machine VSC (MVSC controller. Symmetrical and unsymmetrical faults have been applied in the system to show the effectiveness of the proposed BFCL solution. PMSG wind system, BFCL and their controllers have been implemented by real time hardware in loop (RTHIL setup with real time digital simulator (RTDS and dSPACE. Another significant feature of this work is that the performance of the proposed BFCL is compared with that of series dynamic braking resistor (SDBR. Comparative RTHIL implementation results show that the proposed BFCL is very efficient in improving system fault ride through capability by limiting the fault current and outperforms SDBR.

  12. Seasonal to Decadal-Scale Variability in Satellite Ocean Color and Sea Surface Temperature for the California Current System

    Science.gov (United States)

    Mitchell, B. Greg; Kahru, Mati; Marra, John (Technical Monitor)

    2002-01-01

    Support for this project was used to develop satellite ocean color and temperature indices (SOCTI) for the California Current System (CCS) using the historic record of CZCS West Coast Time Series (WCTS), OCTS, WiFS and AVHRR SST. The ocean color satellite data have been evaluated in relation to CalCOFI data sets for chlorophyll (CZCS) and ocean spectral reflectance and chlorophyll OCTS and SeaWiFS. New algorithms for the three missions have been implemented based on in-water algorithm data sets, or in the case of CZCS, by comparing retrieved pigments with ship-based observations. New algorithms for absorption coefficients, diffuse attenuation coefficients and primary production have also been evaluated. Satellite retrievals are being evaluated based on our large data set of pigments and optics from CalCOFI.

  13. Highlighting patterns of fungal diversity and composition shaped by ocean currents using the East China Sea as a model.

    Science.gov (United States)

    Li, Wei; Wang, Mengmeng; Pan, Haoqin; Burgaud, Gaëtan; Liang, Shengkang; Guo, Jiajia; Luo, Tian; Li, Zhaoxia; Zhang, Shoumei; Cai, Lei

    2018-01-01

    How ocean currents shape fungal transport, dispersal and more broadly fungal biogeography remains poorly understood. The East China Sea (ECS) is a complex and dynamic habitat with different water masses blending microbial communities. The internal transcribed spacer 2 region of fungal rDNA was analysed in water and sediment samples directly collected from the coastal (CWM), Kuroshio (KSWM), Taiwan warm (TWM) and the shelf mixed water mass (MWM), coupled with hydrographic properties measurements, to determine how ocean currents impact the fungal community composition. Almost 9k fungal operational taxonomic units (OTUs) spanning six phyla, 25 known classes, 102 orders and 694 genera were obtained. The typical terrestrial and freshwater fungal genus, Byssochlamys, was dominant in the CWM, while increasing abundance of a specific OTU affiliated with Aspergillus was revealed from coastal to open ocean water masses (TWM and KSWM). Compared with water samples, sediment harboured an increased diversity with distinct fungal communities. The proximity of the Yangtze and Qiantang estuaries homogenizes the surface water and sediment communities. A significant influence of ocean currents on community structure was found, which is believed to reduce proportionally the variation explained by environmental parameters at the scale of the total water masses. Dissolved oxygen and depth were identified as the major parameters structuring the fungal community. Our results indicate that passive fungal dispersal driven by ocean currents and river run-off, in conjunction with the distinct hydrographic conditions of individual water masses, shapes the fungal community composition and distribution pattern in the ECS. © 2017 John Wiley & Sons Ltd.

  14. Fault ride-through enhancement of fixed speed wind turbine using bridge-type fault current limiter

    Directory of Open Access Journals (Sweden)

    Mostafa I. Marei

    2016-05-01

    Full Text Available The interaction between wind energy turbines and the grid results in two main problems, increasing the short-circuit level and reducing the Fault Ride-Through (FRT capability during faults. The objective of this paper is to solve these problems, for fixed speed Wind Energy Systems (WECS, utilizing the bridge-type Fault Current Limiter (FCL with a discharging resistor. A simple cascaded control system is proposed for the FCL to regulate the terminal voltage of the generator and limit the current. The system is simulated on PSCAD/EMTDC software to evaluate the dynamic performance of the proposed WECS compensated by FCL. The simulation results show the potentials of the FCL as a simple and effective method for solving grid interconnection problems of WECS.

  15. Current practice and future prospects for social data in coastal and ocean planning.

    Science.gov (United States)

    Le Cornu, Elodie; Kittinger, John N; Koehn, J Zachary; Finkbeiner, Elena M; Crowder, Larry B

    2014-08-01

    Coastal and ocean planning comprises a broad field of practice. The goals, political processes, and approaches applied to planning initiatives may vary widely. However, all planning processes ultimately require adequate information on both the biophysical and social attributes of a planning region. In coastal and ocean planning practice, there are well-established methods to assess biophysical attributes; however, less is understood about the role and assessment of social data. We conducted the first global assessment of the incorporation of social data in coastal and ocean planning. We drew on a comprehensive review of planning initiatives and a survey of coastal and ocean practitioners. There was significantly more incorporation of social data in multiuse versus conservation-oriented planning. Practitioners engaged a wide range of social data, including governance, economic, and cultural attributes of planning regions and human impacts data. Less attention was given to ecosystem services and social-ecological linkages, both of which could improve coastal and ocean planning practice. Although practitioners recognize the value of social data, little funding is devoted to its collection and incorporation in plans. Increased capacity and sophistication in acquiring critical social and ecological data for planning is necessary to develop plans for more resilient coastal and ocean ecosystems and communities. We suggest that improving social data monitoring, and in particular spatial social data, to complement biophysical data, is necessary for providing holistic information for decision-support tools and other methods. Moving beyond people as impacts to people as beneficiaries, through ecosystem services assessments, holds much potential to better incorporate the tenets of ecosystem-based management into coastal and ocean planning by providing targets for linked biodiversity conservation and human welfare outcomes. © 2014 Society for Conservation Biology.

  16. AC-Chopper-Based Inrush Current Suppressor in a Wind Power Generation System with Squirrel-Cage Induction Machines

    Directory of Open Access Journals (Sweden)

    Sho Shibata

    2018-02-01

    Full Text Available This paper proposes the inrush current suppressor using an AC chopper in a large-capacity wind power generation system (WPGS with two squirrel-cage induction machines (SCIMs, which are switched over depending on the wind speed. The input side of the AC chopper is connected to the source in parallel. The output side of the AC chopper is connected in series with the SCIM through matching transformers. In the proposed inrush current suppressor, the output voltage of the AC chopper is the same as the receiving-end voltage before connecting the SCIM. By gradually decreasing the output voltage of the AC chopper, the applied voltage of the SCIM is gradually increased without the inrush current. The basic principle of the proposed inrush current suppressor is discussed in detail. A computer simulation is implemented to confirm the validity and practicability of the proposed inrush current suppressor using a power system computer-aided design/electromagnetic transients including DC (PSCAD/EMTDC. Simulation results demonstrate that the proposed inrush current suppressor can suppress the inrush current.

  17. EVIDENCE FOR QUASI-ADIABATIC MOTION OF CHARGED PARTICLES IN STRONG CURRENT SHEETS IN THE SOLAR WIND

    Energy Technology Data Exchange (ETDEWEB)

    Malova, H. V. [Scobeltsyn Nuclear Physics Institute of Lomonosov Moscow State University, Moscow (Russian Federation); Popov, V. Yu.; Grigorenko, E. E.; Petrukovich, A. A.; Zelenyi, L. M. [Space Research Institute of the Russian Academy of Sciences, Moscow (Russian Federation); Delcourt, D. [Laboratoire de Physique des Plasmas, Ecole Politechnique, CNRS (France); Sharma, A. S. [Department of Astronomy, University of Maryland, College Park, MD (United States); Khabarova, O. V. [Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation of the Russian Academy of Sciences (IZMIRAN), Moscow (Russian Federation)

    2017-01-01

    We investigate quasi-adiabatic dynamics of charged particles in strong current sheets (SCSs) in the solar wind, including the heliospheric current sheet (HCS), both theoretically and observationally. A self-consistent hybrid model of an SCS is developed in which ion dynamics is described at the quasi-adiabatic approximation, while the electrons are assumed to be magnetized, and their motion is described in the guiding center approximation. The model shows that the SCS profile is determined by the relative contribution of two currents: (i) the current supported by demagnetized protons that move along open quasi-adiabatic orbits, and (ii) the electron drift current. The simplest modeled SCS is found to be a multi-layered structure that consists of a thin current sheet embedded into a much thicker analog of a plasma sheet. This result is in good agreement with observations of SCSs at ∼1 au. The analysis of fine structure of different SCSs, including the HCS, shows that an SCS represents a narrow current layer (with a thickness of ∼10{sup 4} km) embedded into a wider region of about 10{sup 5} km, independently of the SCS origin. Therefore, multi-scale structuring is very likely an intrinsic feature of SCSs in the solar wind.

  18. ORIENTED FOR CAD UNIVERSAL MATHEMATICAL MODEL OF THE EDDY CURRENT PROBE. PART 1. THE RESULTING FIELD OF THE DRIVE WINDING

    Directory of Open Access Journals (Sweden)

    A. G. Dedegkaev

    2015-01-01

    Full Text Available The work relates to the field of CAD methods and means of nondestructive electromagnetic testing of conductive flat products. The problem of constructing mathematical model of the drive winding eddy current probe linearly extended form is polygon in cross section. This allows you to create a universal mathematical model, which includes a model of a simpler shape in cross-section, as a special case. 

  19. Behavior of current sheets at directional magnetic discontinuities in the solar wind at 0.72 AU

    Czech Academy of Sciences Publication Activity Database

    Zhang, T. L.; Russell, C. T.; Zambelli, W.; Vörös, Zoltán; Wang, C.; Cao, J. B.; Jian l, L. K.; Strangeway, R. J.; Balikhin, M.; Baumjohann, W.; Delva, M.; Volwerk, M.; Glassmeier, K.; H.

    2008-01-01

    Roč. 35, č. 24 (2008), L24102/1-L24102/5 ISSN 0094-8276 Grant - others:Austrian Wissenschaftfonds(AT) P20131-N16; NNSFC(CN) 40628003; 973 Program(CN) 2006CB806305; NASA (US) NNG06GC62G Institutional research plan: CEZ:AV0Z30420517 Keywords : solar wind * current sheets * magnetic annihilation Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.959, year: 2008

  20. Wind Farm Stabilization by using DFIG with Current Controlled Voltage Source Converters Taking Grid Codes into Consideration

    Science.gov (United States)

    Okedu, Kenneth Eloghene; Muyeen, S. M.; Takahashi, Rion; Tamura, Junji

    Recent wind farm grid codes require wind generators to ride through voltage sags, which means that normal power production should be re-initiated once the nominal grid voltage is recovered. However, fixed speed wind turbine generator system using induction generator (IG) has the stability problem similar to the step-out phenomenon of a synchronous generator. On the other hand, doubly fed induction generator (DFIG) can control its real and reactive powers independently while being operated in variable speed mode. This paper proposes a new control strategy using DFIGs for stabilizing a wind farm composed of DFIGs and IGs, without incorporating additional FACTS devices. A new current controlled voltage source converter (CC-VSC) scheme is proposed to control the converters of DFIG and the performance is verified by comparing the results with those of voltage controlled voltage source converter (VC-VSC) scheme. Another salient feature of this study is to reduce the number of proportionate integral (PI) controllers used in the rotor side converter without degrading dynamic and transient performances. Moreover, DC-link protection scheme during grid fault can be omitted in the proposed scheme which reduces overall cost of the system. Extensive simulation analyses by using PSCAD/EMTDC are carried out to clarify the effectiveness of the proposed CC-VSC based control scheme of DFIGs.

  1. The 50th Anniversary of the International Indian Ocean Expedition: An Update on Current Planning Efforts and Progress

    Science.gov (United States)

    Hood, Raleigh; D'Adamo, Nick; Burkill, Peter; Urban, Ed; Bhikajee, Mitrasen

    2014-05-01

    The International Indian Ocean Expedition (IIOE) was one of the greatest international, interdisciplinary oceanographic research efforts of all time. Planning for the IIOE began in 1959 and the project officially continued through 1965, with forty-six research vessels participating under fourteen different flags. The IIOE motivated an unprecedented number of hydrographic surveys (and repeat surveys) over the course of the expedition covering the entire Indian Ocean basin. And it was an interdisciplinary endeavor that embraced physical oceanography, chemical oceanography, meteorology, marine biology, marine geology and geophysics. The end of 2015 will mark the 50th Anniversary of the completion of the IIOE. In the 50 years since the IIOE three fundamental changes have taken place in ocean science. The first is the deployment of a broad suite of oceanographic sensors on satellites that have dramatically improved the characterization of both physical and biological oceanographic variability. The second is the emergence of new components of the ocean observing system, most notably remote sensing and Argo floats. And the third is the development of ocean modeling in all its facets from short-term forecasting to seasonal prediction to climate projections. These advances have revolutionized our understanding of the global oceans, including the Indian Ocean. Compared to the IIOE era, we now have the capacity to provide a much more integrated picture of the Indian Ocean, especially if these new technologies can be combined with targeted and well-coordinated in situ measurements. In this presentation we report on current efforts to motivate an IIOE 50th Anniversary Celebration (IIOE-2). We envision this IIOE-2 as a 5-year expedition and effort beginning in 2015 and continuing through to 2020. An important objective of our planning efforts is assessing ongoing and planned research activities in the Indian Ocean in the 2015 to 2020 time frame, with the goal of embracing and

  2. Seaglider surveys at Ocean Station Papa: Circulation and water mass properties in a meander of the North Pacific Current

    Science.gov (United States)

    Pelland, Noel A.; Eriksen, Charles C.; Cronin, Meghan F.

    2016-09-01

    A Seaglider autonomous underwater vehicle augmented the Ocean Station Papa (OSP; 50°N, 145°W) surface mooring, measuring spatial structure on scales relevant to the monthly evolution of the moored time series. During each of three missions from June 2008 to January 2010, a Seaglider made biweekly 50 km × 50 km surveys in a bowtie-shaped survey track. Horizontal temperature and salinity gradients measured by these surveys were an order of magnitude stronger than climatological values and sometimes of opposite sign. Geostrophically inferred circulation was corroborated by moored acoustic Doppler current profiler measurements and AVISO satellite altimetry estimates of surface currents, confirming that glider surveys accurately resolved monthly scale mesoscale spatial structure. In contrast to climatological North Pacific Current circulation, upper-ocean flow was modestly northward during the first half of the 18 month survey period, and weakly westward during its latter half, with Rossby number O>(0.01>). This change in circulation coincided with a shift from cool and fresh to warm, saline, oxygen-rich water in the upper-ocean halocline, and an increase in vertical fine structure there and in the lower pycnocline. The anomalous flow and abrupt water mass transition were due to the slow growth of an anticyclonic meander within the North Pacific Current with radius comparable to the scale of the survey pattern, originating to the southeast of OSP.

  3. The 2015-16 El Niño - Birth, Evolution and Teleconnections from Scatterometer Observations of the Ocean Surface Winds

    Science.gov (United States)

    Hristova-Veleva, S. M.; Lee, T.; Stiles, B. W.; Rodriguez, E.; Turk, J.; Haddad, Z. S.

    2016-12-01

    The 2015-16 El Niño is one of the strongest events observed during the modern instrumentation period, rivaling the two big ones observed by satellites during 1982-83 and 1997-98. Yet, the precipitation anomalies differ from the expectations that were based on these two events. While El Niño events have a significant impact on the entire Earth System, they are most easily visible in measurements of sea surface temperature (SST), sea surface height (SSH) and ocean winds near the surface. In fact, the signature eastward-blowing anomalous surface winds in the Western and Central Tropical Pacific are the pre-cursor and the main driver of the El Nino events. Here we use observations from NASA's RapidScat, EUMETSAT's ASCAT and also from collocated ECMWF analysis to monitor the evolution of the anomalous winds associated with the 2015-16 El Niño. To detect the El Nino signal, we first compute monthly means of the wind speed, wind components and wind convergence. We then perform a low-pass filter to extract the components of the larger-scale circulation and compute the 2015-2016 anomalies with respect to the corresponding months of 2014-2015. We find fast-evolving wind anomalies and relate them to the evolution of the SST field as depicted in the observations-based OSTIA product. Furthermore, we investigate the relationship between the GPM-observed precipitation and the surface wind convergence observed by the scatterometers. El Niño is known to have basin to global scale teleconnections. In addition to the characterization of the changes in the tropical Pacific, we will also describe the associated changes in the North and South Pacific. In particular, a strong anticyclonic anomaly is observed in the north-eastern Pacific. This anomalous circulation is likely associated with the subsidence (divergent) region of a stronger-than-normal Hadley cell, leading to modification of the midlatitude storm tracks and the related precipitation anomalies. Furthermore, these

  4. H∞ Current Damping Control of DFIG based Wind Farm for Sub-Synchronous Control Interaction Mitigation

    DEFF Research Database (Denmark)

    Wang, Yun; Wu, Qiuwei; Yang, Rong

    2018-01-01

    This paper proposes an H∞ damping controller for the doubly-fed induction generator (DFIG) based wind farm (WF) to mitigate sub-synchronous control interactions (SSCI) with series capacitor compensated lines. A multi-input multi-output (MIMO) uncertain state-space model is developed to reflect...

  5. Wind atlas for South Africa (WASA): Project overview and current status

    CSIR Research Space (South Africa)

    Szewczuk, S

    2010-08-31

    Full Text Available The goal of the South African Wind Energy Programme (SAWEP) is to reduce greenhouse gas emissions generated by thermal power in the national inter-connected system. SAWEP has six main expected outcomes: increased public sector incremental cost...

  6. HVDC Connected Offshore Wind Power Plants: Review and Outlook of Current Research

    DEFF Research Database (Denmark)

    Glasdam, Jakob; Zeni, Lorenzo; Gryning, Mikkel

    2013-01-01

    and the PED widely used in the wind turbine generators (WTGs). Challenges hereto include PED control system interaction (from a stability point of view), assessment of the quality of vendor supplied control systems and their robustness against e.g. short circuits and load rejection. Furthermore, the outcome...

  7. Satellite-tracked drifting buoy observations in the south equatorial current in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Shetye, S.R.; Michael, G.S.

    two buoys moved north and the third moved south. Over the open sea regime the buoys moved with a speed of approximately 30 cm/s at an angle of about 35 degrees to the left of the wind. The overall tendencies seen in the buoy drift are similar to those...

  8. Surface currents in the equatorial Indian Ocean during spring and fall - An altimetry based analysis

    Digital Repository Service at National Institute of Oceanography (India)

    Antony, M.K.; Somayajulu, Y.K.

    to just south of the equator, whereas, the fall jet derived between October and December is almost symmetrical about the equator. These jets are found to be about 400 km wide with a speed of 70-80 cm/sec. Maximum duration of these wind-driven, eastward...

  9. Current observations from a looking down vertical V-ADCP: interaction with winds and tide? The case of Giglio Island (Tyrrhenian Sea, Italy

    Directory of Open Access Journals (Sweden)

    Laura Cutroneo

    2017-04-01

    Full Text Available In the context of the environmental monitoring of the Concordia wreck removal project, measurements of currents, winds and sea level height were made along the eastern coast of the Giglio Island, Tyrrhenian Sea (Italy, during 2012–2013. The aim of the study was to investigate the effect of atmospheric forcing and periodic sea-level changes on the coastal currents. Normalised Cross-Correlation Function analysis allowed us to correlate these observations. A marked inter-seasonal variability was found in both current and local wind velocity observations but a significant level of correlation between the data was only found during strong wind events. Current and wind directions appeared to be uncorrelated and current measurements showed a predominant NW–SE direction, presumably linked to the shape and orientation of Giglio Island itself. During strong winds from the SSE, current flow was towards the NNW but it suddenly switched from the NNW to the SE at the end of wind events. The results show that, at Giglio Island, currents are principally dominated by the general cyclonic Tyrrhenian circulation, and, secondly, by strong wind events. The sea level had no effects on the current regime.

  10. Oceanic fronts along 45 degrees across Antarctic Circumpolar Current during austral summer 2004

    Digital Repository Service at National Institute of Oceanography (India)

    AnilKumar, N.; Dash, M.K.; Luis, A.J.; RameshBabu, V.; Somayajulu, Y.K.; Sudhakar, M.; Pandey, P.C.

    the positioning and structure of oceanic fronts. One of the major problems that hamper a comprehensive understanding of the physical and dynamical processes of the SO is the scarcity of in situ data from the western Indian Ocean during all seasons... . The average changes in the surface temperature of the PF (5.5 ? 2.7 ?C) showed a marginal differen ce when compared with Holliday and Read 2 (5.8 ~ 2 ?C), Sparrow et al. 4 (5 ~ 3.8 ?C), and Lutj e- harms and Valentine 12 (4.1 ~ 2.5 ?C). A...

  11. Current and other data from fixed platforms from the South Atlantic Ocean as part of the International Decade of Ocean Exploration / International Ocean Studies / First Dynamic Response and Kinematics Experiment in the Drake Passage (IDOE/ISOS/FDRAKE) from 1975-02-22 to 1980-02-24 (NODC Accession 9500011)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current and other data were collected from fixed platforms in the South Atlantic Ocean from 22 February 1975 to 24 February 1980. Data were collected by the Texas...

  12. Peak current mode control of three-phase boost rectifiers in discontinuous conduction mode for small wind power generators

    Energy Technology Data Exchange (ETDEWEB)

    Carranza, O. [Escuela Superior de Computo, Instituto Politecnico Nacional (Mexico); Garcera, G.; Figueres, E. [Grupo de Sistemas Electronicos Industriales del Departamento de Ingenieria Electronica, Universidad Politecnica de Valencia (Spain); Gonzalez, L.G. [Departamento de Ingenieria Electronica y Comunicaciones, Universidad de los Andes (Venezuela)

    2010-08-15

    This paper presents a peak current mode control scheme of a boost rectifier with low distortion of the input current for wind power systems based on permanent magnet synchronous generators with variable speed operation. The three-phase boost rectifier is operated in discontinuous conduction mode (DCM), and power factor correction techniques are applied. It is shown that the DCM operation significantly reduces the total harmonic distortion of the currents in the permanent magnet synchronous generator, increasing the power factor of the system, so that the vibrations and mechanical stress of the generator are minimized. The characteristics of the DCM boost rectifier are studied considering: (1) the series resistance of the inductors; (2) the modeling and adjustment of peak current mode control yielding a stable loop; (3) the design of an input filter that reduces the switching noise in the currents of the generator. (author)

  13. Ocean currents and acoustic backscatter data from shipboard ADCP measurements at three North Atlantic seamounts between 2004 and 2015.

    Science.gov (United States)

    Mohn, Christian; Denda, Anneke; Christiansen, Svenja; Kaufmann, Manfred; Peine, Florian; Springer, Barbara; Turnewitsch, Robert; Christiansen, Bernd

    2018-04-01

    Seamounts are amongst the most common physiographic structures of the deep-ocean landscape, but remoteness and geographic complexity have limited the systematic collection of integrated and multidisciplinary data in the past. Consequently, important aspects of seamount ecology and dynamics remain poorly studied. We present a data collection of ocean currents and raw acoustic backscatter from shipboard Acoustic Doppler Current Profiler (ADCP) measurements during six cruises between 2004 and 2015 in the tropical and subtropical Northeast Atlantic to narrow this gap. Measurements were conducted at seamount locations between the island of Madeira and the Portuguese mainland (Ampère, Seine Seamount), as well as east of the Cape Verde archipelago (Senghor Seamount). The dataset includes two-minute ensemble averaged continuous velocity and backscatter profiles, supplemented by spatially gridded maps for each velocity component, error velocity and local bathymetry. The dataset is freely available from the digital data library PANGAEA at https://doi.pangaea.de/10.1594/PANGAEA.883193.

  14. The rôle of the complete Coriolis force in cross-equatorial flow of abyssal ocean currents

    Science.gov (United States)

    Stewart, A. L.; Dellar, P. J.

    Ocean currents flowing close to or across the equator are strongly constrained by the change in sign of f, the locally vertical component of the Earth's rotation vector, across the equator. We investigate these currents using a shallow water model that includes both the locally vertical and locally horizontal components of the Earth's rotation vector, thus accounting for the complete Coriolis force. We therefore avoid making the so-called "traditional approximation" that retains only the part of the Coriolis force associated with the locally vertical component of the rotation vector. Including the complete Coriolis force contributes an additional term to the fluid's potential vorticity, which may partially balance the change in sign of f as fluid crosses the equator over suitably shaped bathymetry. We focus on the Antarctic Bottom Water, which crosses the equator northwards in the western Atlantic ocean where the local bathymetry forms an almost-zonal channel. We show that this bathymetry facilitates the current's equatorial crossing via the action of the "non-traditional" component of the Coriolis force. We illustrate this process using both analytical and numerical solutions for flow of an abyssal current over idealised equatorial topography. We also consider the one-dimensional geostrophic adjustment of a body of fluid across the equator, and show that the "non-traditional" contribution to the fluid's angular momentum permits a larger cross-equatorial transport. These results underline the importance of including the complete Coriolis force in studies of the equatorial ocean, particularly in the weakly-stratified abyssal ocean where the non-traditional component is most pronounced.

  15. Transient voltage control of a DFIG-based wind power plant for suppressing overvoltage using a reactive current reduction loop

    Directory of Open Access Journals (Sweden)

    Geon Park

    2016-01-01

    Full Text Available This paper proposes a transient voltage control scheme of a doubly fed induction generator (DFIG-based wind power plant (WPP using a reactive current reduction loop to suppress the overvoltage at a point of interconnection (POI and DFIG terminal after a fault clearance. The change of terminal voltage of a DFIG is monitored at every predefined time period to detect the fault clearance. If the voltage change exceeds a set value, then the reactive current reduction loop reduces the reactive current reference in the DFIG controller using the step function. The reactive current injection of DFIGs in a WPP is rapidly reduced, and a WPP can rapidly suppress the overvoltage at a fault clearance because the reactive current reference is reduced. Using an electromagnetic transients program–released version (EMTP–RV simulator, the performance of the proposed scheme was validated for a model system comprising 20 units of a 5-MW DFIG considering various scenarios, such as fault and wind conditions. Test results show that the proposed scheme enables a WPP to suppress the overvoltage at the POI and DFIG terminal within a short time under grid fault conditions.

  16. Development of Ground Coils with Low Eddy Current Loss by Applying the Compression Molding Method after the Coil Winding

    Science.gov (United States)

    Suzuki, Masao; Aiba, Masayuki; Takahashi, Noriyuki; Ota, Satoru; Okada, Shigenori

    In a magnetically levitated transportation (MAGLEV) system, a huge number of ground coils will be required because they must be laid for the whole line. Therefore, stable performance and reduced cost are essential requirements for the ground coil development. On the other hand, because the magnetic field changes when the superconducting magnet passes by, an eddy current will be generated in the conductor of the ground coil and will result in energy loss. The loss not only increases the magnetic resistance for the train running but also brings an increase in the ground coil temperature. Therefore, the reduction of the eddy current loss is extremely important. This study examined ground coils in which both the eddy current loss and temperature increase were small. Furthermore, quantitative comparison for the eddy current loss of various magnet wire samples was performed by bench test. On the basis of the comparison, a round twisted wire having low eddy current loss was selected as an effective ground coil material. In addition, the ground coils were manufactured on trial. A favorable outlook to improve the size accuracy of the winding coil and uneven thickness of molded resin was obtained without reducing the insulation strength between the coil layers by applying a compression molding after winding.

  17. Collision and displacement vulnerability among marine birds of the California Current System associated with offshore wind energy infrastructure

    Science.gov (United States)

    Adams, Josh; Kelsey, Emily C.; Felis, Jonathan J.; Pereksta, David M.

    2016-10-27

    With growing climate change concerns and energy constraints, there is an increasing need for renewable energy sources within the United States and globally. Looking forward, offshore wind-energy infrastructure (OWEI) has the potential to produce a significant proportion of the power needed to reach our Nation’s renewable energy goal. Offshore wind-energy sites can capitalize open areas within Federal waters that have persistent, high winds with large energy production potential. Although there are few locations in the California Current System (CCS) where it would be acceptable to build pile-mounted wind turbines in waters less than 50 m deep, the development of technology able to support deep-water OWEI (>200 m depth) could enable wind-energy production in the CCS. As with all human-use of the marine environment, understanding the potential impacts of wind-energy infrastructure on the marine ecosystem is an integral part of offshore wind-energy research and planning. Herein, we present a comprehensive database to quantify marine bird vulnerability to potential OWEI in the CCS (see https://doi.org/10.5066/F79C6VJ0). These data were used to quantify marine bird vulnerabilities at the population level. For 81 marine bird species present in the CCS, we created three vulnerability indices: Population Vulnerability, Collision Vulnerability, and Displacement Vulnerability. Population Vulnerability was used as a scaling factor to generate two comprehensive indicies: Population Collision Vulnerability (PCV) and Population Displacement Vulnerability (PDV). Within the CCS, pelicans, terns (Forster’s [Sterna forsteri], Caspian [Hydroprogne caspia], Elegant [Thalasseus elegans], and Least Tern [Sternula antillarum]), gulls (Western [Larus occidentalis] and Bonaparte’s Gull [Chroicocephalus philadelphia]), South Polar Skua (Stercorarius maccormicki), and Brandt’s Cormorant (Phalacrocorax penicillatus) had the greatest PCV scores. Brown Pelican (Pelicanus occidentalis

  18. A pivotal role for ocean eddies in the distribution of microbial communities across the Antarctic Circumpolar Current.

    Directory of Open Access Journals (Sweden)

    Siddarthan Venkatachalam

    Full Text Available Mesoscale variability and associated eddy fluxes play crucial roles in ocean circulation dynamics and the ecology of the upper ocean. In doing so, these features are biologically important, providing a mechanism for the mixing and exchange of nutrients and biota within the ocean. Transient mesoscale eddies in the Southern Ocean are known to relocate zooplankton communities across the Antarctic Circumpolar Current (ACC and are important foraging grounds for marine top predators. In this study we investigated the role of cyclonic and anti-cyclonic eddies formed at the South-West Indian Ridge on the spatial variability and diversity of microbial communities. We focused on two contrasting adjacent eddies within the Antarctic Polar Frontal Zone to determine how these features may influence the microbial communities within this region. The water masses and microbiota of the two eddies, representative of a cyclonic cold core from the Antarctic zone and an anti-cyclonic warm-core from the Subantarctic zone, were compared. The data reveal that the two eddies entrain distinct microbial communities from their points of origin that are maintained for up to ten months. Our findings highlight the ecological impact that changes, brought by the translocation of eddies across the ACC, have on microbial diversity.

  19. Evaluation of wind vectors measured by QuikSCAT using ocean buoy data along the Galician coast (NW Iberian Peninsula)

    Science.gov (United States)

    Alvarez, I.; Gomez-Gesteira, M.; deCastro, M.; Sousa, M. C.; Dias, J. M.; Santos, F.

    2012-04-01

    Wind above sea surface constitutes a key parameter to analyze coastal phenomena, like upwelling in the NW part of the Iberian Peninsula. The present work analyzes the accuracy of QuikSCAT for the period 2000-2009 by comparing satellite data with in situ data from three buoys placed along the NW coast of the Iberian Peninsula. The use of these long data series has two main objectives, on the one hand, the margin of error diminishes with the extent of the series and, on the other hand, it allows capturing the high inter-annual variability of the area. According to previous studies, the wet season is characterized by a high variability, in such a way that wind patterns change from year to year. The comparison confirms a low skill of QuikSCAT for low speed winds (<3 m/s) as previously pointed out by other authors. Once these winds were discarded, QuikSCAT revealed a higher accuracy for winds within the range 6-12 m/s. In direction, winds blowing from coast seem to be less accurately calculated by the satellite. Statistical results were similar for the three buoys in spite of the different coastal orientations. In average, the RMSE and bias for wind speed were 1.5 m/s and 0.2 m/s, respectively. Statistical data were also similar for wind direction, with the mean RMSE on the order of 34° and the mean bias on the order of 4° in absolute value. These statistical parameters are at least as accurate as those calculated in other near-shore areas all over the world. In particular, the bias was observed to be lower (in absolute value) than measured by most of the authors, which is possibly due to the high percentage of sampled winds lying within the interval [6-12] m/s, where satellite measurements are more accurate.

  20. Current meter data from moored current meter casts in the Caribbean Sea as part of the Ocean Thermal Energy Conversion (OTEC) project from 1979-09-27 to 1979-12-01 (NODC Accession 8100607)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data were collected using moored current meter casts in the Caribbean Sea from September 27, 1979 to December 1, 1979. Data were submitted by...

  1. A diatom–conductivity transfer function for reconstructing past changes in the Southern Hemisphere westerly winds over the Southern Ocean

    OpenAIRE

    Saunders Krystyna; Hodgson Dominic; McMurtrie Shelley; Grosjean; Martin

    2015-01-01

    Sub Antarctic islands are ideally placed to reconstruct past changes in Southern Hemisphere westerly wind behaviour. They lie within their core belt (50–60°S) and the strong winds deliver sea salt ions to the islands resulting in a west to east conductivity gradient in their water bodies. This means that the stronger (or weaker) the winds the higher (or lower) the conductivity values measured in the water bodies. A survey of the water chemistry and diatom assemblages of lakes and ponds on sub...

  2. Hydrothermal and Chemosynthetic Ecosystems in the Southern Ocean: Current Knowledge on their Biology Paper 217790

    Science.gov (United States)

    Linse, K.; Rogers, A. D.; Bohrmann, G.; Copley, J.; Tyler, P. A.

    2017-12-01

    The existence of hydrothermal and other chemosynthetic ecosystems is not surprising in the Antarctic, with its active volcanoes, mid-ocean ridges and back-arc basins, and abundance of marine mammals. In the last two decades a variety of active chemosynthetic ecosystems have been discovered in the Southern Ocean, including low- and high-temperature hydrothermal vents, methane seeps, and whalefalls. Here a summary of the data from the known chemosynthetic communites will be presented, comparing the faunas of vent sites in the Bransfield Strait with those of the East Scotia Ridge (ESR) and the South Sandwich Arc, assessing the fauna at the South Georgia methane seep sites, and discussing the fauna on Antarctic whale falls. As the faunal assemblages of the ESR vents are the most studied in detail to date, this talk therefore focusses on the diversity and composition of the ESR macrofaunal assemblages, their foodweb structure and microdistributions in relation to fluid chemistry and microbiology, and their phylogenetic and biogeographic relationships. The Southern Ocean drives the global ocean conveyor belt, and is suggested to be the centre of origin for global deep-sea fauna, as well as a region of high deep-sea species diversity. In the context of chemosynthetic environments, it may provide a gateway connecting the global vent and seep systems. The mostly endemic species of Southern Ocean vent macrofauna show links to either one or more oceans (Atlantic, Indian, and Pacific), with some evidence for circum-Antarctic connection. The ESR species Gigantopelta chessoia, Kiwa tyleri and Vulcanolepas scotiaensis have their closest known relatives at the Longqi Vent Field on the Southwest Indian Ridge (SWIR), and one species of polynoid polychaete is known from ESR and SWIR vents. Meanwhile, Lepetdrilus sp. and a vesiocomyid clam are linked with species in the Atlantic vent fields. The stichasterid Paulasterias tyleri, the polychaete Rarricirrus jennae and the anthozoan

  3. A linearly controlled direct-current power source for high-current inductive loads in a magnetic suspension wind tunnel

    Science.gov (United States)

    Tripp, John S.; Daniels, Taumi S.

    1990-01-01

    The NASA Langley 6 inch magnetic suspension and balance system (MSBS) requires an independently controlled bidirectional DC power source for each of six positioning electromagnets. These electromagnets provide five-degree-of-freedom control over a suspended aerodynamic test model. Existing power equipment, which employs resistance coupled thyratron controlled rectifiers as well as AC to DC motor generator converters, is obsolete, inefficient, and unreliable. A replacement six phase bidirectional controlled bridge rectifier is proposed, which employs power MOSFET switches sequenced by hybrid analog/digital circuits. Full load efficiency is 80 percent compared to 25 percent for the resistance coupled thyratron system. Current feedback provides high control linearity, adjustable current limiting, and current overload protection. A quenching circuit suppresses inductive voltage impulses. It is shown that 20 kHz interference from positioning magnet power into MSBS electromagnetic model position sensors results predominantly from capacitively coupled electric fields. Hence, proper shielding and grounding techniques are necessary. Inductively coupled magnetic interference is negligible.

  4. Changing currents: a strategy for understanding and predicting the changing ocean circulation.

    Science.gov (United States)

    Bryden, Harry L; Robinson, Carol; Griffiths, Gwyn

    2012-12-13

    Within the context of UK marine science, we project a strategy for ocean circulation research over the next 20 years. We recommend a focus on three types of research: (i) sustained observations of the varying and evolving ocean circulation, (ii) careful analysis and interpretation of the observed climate changes for comparison with climate model projections, and (iii) the design and execution of focused field experiments to understand ocean processes that are not resolved in coupled climate models so as to be able to embed these processes realistically in the models. Within UK-sustained observations, we emphasize smart, cost-effective design of the observational network to extract maximum information from limited field resources. We encourage the incorporation of new sensors and new energy sources within the operational environment of UK-sustained observational programmes to bridge the gap that normally separates laboratory prototype from operational instrument. For interpreting the climate-change records obtained through a variety of national and international sustained observational programmes, creative and dedicated UK scientists should lead efforts to extract the meaningful signals and patterns of climate change and to interpret them so as to project future changes. For the process studies, individual scientists will need to work together in team environments to combine observational and process modelling results into effective improvements in the coupled climate models that will lead to more accurate climate predictions.

  5. Panorama 2011: Ocean renewable energies

    International Nuclear Information System (INIS)

    Demoulin, P.; Vinot, S.

    2011-01-01

    Our society is looking increasingly to renewable energy sources in the face of the energy and environmental challenges with which it is grappling. As far as ocean renewable energies are concerned, a wide range of technologies is currently being experimented with, including wind power and energy derived from waves and tidal currents. They are all at varying levels of maturity, and bring with them very different technical and economic challenges. (author)

  6. Spatial and seasonal patterns of fine-scale to mesoscale upper ocean dynamics in an Eastern Boundary Current System

    Science.gov (United States)

    Grados, Daniel; Bertrand, Arnaud; Colas, François; Echevin, Vincent; Chaigneau, Alexis; Gutiérrez, Dimitri; Vargas, Gary; Fablet, Ronan

    2016-03-01

    The physical forcing of the ocean surface includes a variety of energetic processes, ranging from internal wave (IW) to submesoscale and mesoscale, associated with characteristic horizontal scales. While the description of mesoscale ocean dynamics has greatly benefited from the availability of satellite data, observations of finer scale patterns remain scarce. Recent studies showed that the vertical displacements of the oxycline depth, which separates the well-mixed oxygenated surface layer from the less oxygenated deeper ocean, estimated by acoustics, provide a robust proxy of isopycnal displacements over a wide range of horizontal scales. Using a high-resolution and wide-range acoustic data set in the Northern Humboldt Current System (NHCS) off Peru, the spatial and temporal patterns of fine-scale-to-mesoscale upper ocean dynamics are investigated. The spectral content of oxycline/pycnocline profiles presents patterns characteristic of turbulent flows, from the mesoscale to the fine scale, and an energization at the IW scale (2 km-200 m). On the basis of a typology performed on 35,000 structures we characterized six classes of physical structures according to their shape and scale range. The analysis reveals the existence of distinct features for the fine-scale range below ∼2-3 km, and clearly indicates the existence of intense IW and submesoscale activity over the entire NHCS region. Structures at scales smaller than ∼2 km were more numerous and energetic in spring than in summer. Their spatiotemporal variability supports the interpretation that these processes likely relate to IW generation by interactions between tidal flows, stratification and the continental slope. Given the impact of the physical forcing on the biogeochemical and ecological dynamics in EBUS, these processes should be further considered in future ecosystem studies based on observations and models. The intensification of upper ocean stratification resulting from climate change makes such

  7. Decadal fCO2 trends in global ocean margins and adjacent boundary current-influenced areas

    Science.gov (United States)

    Wang, Hongjie; Hu, Xinping; Cai, Wei-Jun; Sterba-Boatwright, Blair

    2017-09-01

    Determination of the rate of change of sea surface CO2 fugacity (fCO2) is important, as the fCO2 gradient between the atmosphere and the ocean determines the direction of CO2 flux and hence the fate of this greenhouse gas. Using a newly available, community-based global CO2 database (Surface Ocean CO2 Atlas Version 3 coastal data set) and a newly developed statistical method, we report that the global ocean margins (within 400 km offshore, 30°S-70°N) fCO2 temporal trends on decadal time scales (1.93 ± 1.59 μatm yr-1) closely follow the atmospheric fCO2 increase rate (1.90 ± 0.06 μatm yr-1) in the Northern Hemisphere but are lower (1.35 ± 0.55 μatm yr-1) in the Southern Hemisphere, reflecting dominant atmospheric forcing in conjunction with different warming rates in the two hemispheres. In addition to the atmospheric fCO2 forcing, a direct warming effect contributes more to fCO2 increase in the western boundary current-influenced areas, while intensified upwelling contributes more to fCO2 increase in eastern boundary current-influenced areas.

  8. Steering of Upper Ocean Currents and Fronts by the Topographically Constrained Abyssal Circulation

    Science.gov (United States)

    2008-07-06

    Soya Straits (labeled in Fig. 5a). Two layers are open through Tsushima and Tsugaru, but only the top layer through Soya , consistent with the sill...130°E 135°E 140°E 1 . TSS TGS : Tauahiaa St ran : Taugaru Strait MsU 5 I 4 ss : Soya Strait A( / IS i laaiya Strait D( Y...Sv) and out through the Tsugaru Strait (2/3) and the Soya Strait (1/3) and by wind stress forcing from (a) HRsm, (b) EC10M, (c) EC1000, (d) Na, (e

  9. Ekman Upwelling, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes science quality Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  10. The impact of the ocean observing system on estimates of the California current circulation spanning three decades

    Science.gov (United States)

    Moore, Andrew M.; Jacox, Michael G.; Crawford, William J.; Laughlin, Bruce; Edwards, Christopher A.; Fiechter, Jérôme

    2017-08-01

    Data assimilation is now used routinely in oceanography on both regional and global scales for computing ocean circulation estimates and for making ocean forecasts. Regional ocean observing systems are also expanding rapidly, and observations from a wide array of different platforms and sensor types are now available. Evaluation of the impact of the observing system on ocean circulation estimates (and forecasts) is therefore of considerable interest to the oceanographic community. In this paper, we quantify the impact of different observing platforms on estimates of the California Current System (CCS) spanning a three decade period (1980-2010). Specifically, we focus attention on several dynamically related aspects of the circulation (coastal upwelling, the transport of the California Current and the California Undercurrent, thermocline depth and eddy kinetic energy) which in many ways describe defining characteristics of the CCS. The circulation estimates were computed using a 4-dimensional variational (4D-Var) data assimilation system, and our analyses also focus on the impact of the different elements of the control vector (i.e. the initial conditions, surface forcing, and open boundary conditions) on the circulation. While the influence of each component of the control vector varies between different metrics of the circulation, the impact of each observing system across metrics is very robust. In addition, the mean amplitude of the circulation increments (i.e. the difference between the analysis and background) remains relatively stable throughout the three decade period despite the addition of new observing platforms whose impact is redistributed according to the relative uncertainty of observations from each platform. We also consider the impact of each observing platform on CCS circulation variability associated with low-frequency climate variability. The low-frequency nature of the dominant climate modes in this region allows us to track through time the

  11. The inclusion of ocean-current effects in a tidal-current model as forcing in the convection term and its application to the mesoscale fate of CO2 seeping from the seafloor

    Science.gov (United States)

    Sakaizawa, Ryosuke; Kawai, Takaya; Sato, Toru; Oyama, Hiroyuki; Tsumune, Daisuke; Tsubono, Takaki; Goto, Koichi

    2018-03-01

    The target seas of tidal-current models are usually semi-closed bays, minimally affected by ocean currents. For these models, tidal currents are simulated in computational domains with a spatial scale of a couple hundred kilometers or less, by setting tidal elevations at their open boundaries. However, when ocean currents cannot be ignored in the sea areas of interest, such as in open seas near coastlines, it is necessary to include ocean-current effects in these tidal-current models. In this study, we developed a numerical method to analyze tidal currents near coasts by incorporating pre-calculated ocean-current velocities. First, a large regional-scale simulation with a spatial scale of several thousand kilometers was conducted and temporal changes in the ocean-current velocity at each grid point were stored. Next, the spatially and temporally interpolated ocean-current velocity was incorporated as forcing into the cross terms of the convection term of a tidal-current model having computational domains with spatial scales of hundreds of kilometers or less. Then, we applied this method to the diffusion of dissolved CO2 in a sea area off Tomakomai, Japan, and compared the numerical results and measurements to validate the proposed method.

  12. Current issues in developing safety culture while establishing wind energy power plants in India

    Energy Technology Data Exchange (ETDEWEB)

    Gowda, M.C.M.; Repaka, B.; Gowda, P. [MSRIT Research Centre, Bangalore (India); Chandrashekar, R. [SaIT, Bangalore (India)

    2012-07-01

    Safety is important to every one working in the various organizations. They want to be safe when coming to work, at the time of work and going back to home. The ultimate aim of every worker is to work for the needs/money and or satisfaction where these would get prioritized according to the individuals. People don't want accidents to happen. People don't want to get themselves injured nor their colleagues. People would like and love to work in a company which cares for them and keeps them safe. Having said this then what makes them meet with or see an accident in the wind farm? Yes it is the unsafe act and unsafe condition which causes an accident in the wind farm. The present study put forward the factors /issues that influence people behaviors as part of weakening the safety culture to perform an unsafe act or to ignore and work in an unsafe condition. (Author)

  13. Dynamics of the east India coastal current. 1. Analytic solutions forced by interior Ekman pumping and local alongshore winds

    Digital Repository Service at National Institute of Oceanography (India)

    Shankar, D.; McCreary, J.P.; Han, W.; Shetye, S.R.

    linear, continuously stratified model is used to investigate how forcing by interior Ekman pumping and local alongshore winds affects the East India Coastal Current (EICC). Solutions are found analytically to an approximate version of the equations...) by f_ D n(z')dz', and integrate over the water column. After a few integrations by parts and the use of (2)-(4c), it follows that O + u. - fv. + p. - F. + V u , ( a) O + v, + fu, + p,. = G, + V v , (6b) 0 + - = 0 + ( ) Cn 2 P ( e...

  14. Energy from the ocean. Report of the Committee on Science and Technology, U. S. House of Representatives, Ninety-Fifth Congress, Second Session by the Science Policy Research Division, Congressional Research Service, Library of Congress

    Energy Technology Data Exchange (ETDEWEB)

    1978-01-01

    In the area of renewable sources of energy from the ocean, the report includes chapters on ocean thermal energy conversion; energy from ocean waves; energy from ocean currents; energy from tides; energy from oceanic winds; energy from salinity gradients; and energy from oceanic bioconversion. Also covered are the nonrenewable sources of energy from the ocean with chapters on deep ocean oil and gas; offshore geothermal energy; and offshore hard mineral energy resources. The report concludes with a bibliography and a selection of current articles on the general subject of the energy potential of the oceans.

  15. A probabilistic method for the estimation of ocean surface currents from short time series of HF radar data

    Science.gov (United States)

    Guérin, Charles-Antoine; Grilli, Stéphan T.

    2018-01-01

    We present a new method for inverting ocean surface currents from beam-forming HF radar data. In contrast with the classical method, which inverts radial currents based on shifts of the main Bragg line in the radar Doppler spectrum, the method works in the temporal domain and inverts currents from the amplitude modulation of the I and Q radar time series. Based on this principle, we propose a Maximum Likelihood approach, which can be combined with a Bayesian inference method assuming a prior current distribution, to infer values of the radial surface currents. We assess the method performance by using synthetic radar signal as well as field data, and systematically comparing results with those of the Doppler method. The new method is found advantageous for its robustness to noise at long range, its ability to accommodate shorter time series, and the possibility to use a priori information to improve the estimates. Limitations are related to current sign errors at far-ranges and biased estimates for small current values and very short samples. We apply the new technique to a data set from a typical 13.5 MHz WERA radar, acquired off of Vancouver Island, BC, and show that it can potentially improve standard synoptic current mapping.

  16. Chilean jagged lobster, Projasus bahamondei, in the southeastern Pacific Ocean: current state of knowledge

    Directory of Open Access Journals (Sweden)

    Patricio M Arana

    2014-03-01

    Full Text Available The Chilean jagged lobster (Projasus bahamondei is a deep-water crustacean (175-550 m occurring in certain areas of the southeastern Pacific Ocean, including the Nazca Ridge, Desventuradas Islands, the Juan Fernandez archipelago and ridge, and the continental slope off the central coast of Chile. This review describes the taxonomic status, geographical and bathymetric distribution, some biological aspects and habitat characteristics of this species. Additionally, both artisanal and industrial exploitation attempts made within the region are detailed, as well as fishing operation results, chemical composition, different elaboration procedures and the destination of the catch. The main objectives of this review are to contribute to the knowledge of P. bahamondei as a component of the deep-sea ecosystem and to highlight its importance as a potential fishery resource.

  17. CURRENT DIRECTION, WIND GUST and other data from FIXED PLATFORM from 1974-02-23 to 1974-04-25 (NCEI Accession 7601418)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter and other data were collected from fixed platforms from 23 February 1974 to 25 April 1974. Data were collected by Oregon State University (OSU) as part...

  18. Moored current meter and wind recorder measurement near Point Conception, California: The 1983 OPUS Observations, from 1983-04-01 to 1983-07-29 (NODC Accession 8600041)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The OPUS (Organization of Persistent Upwelling Structures) program deployed two current meter (VMCM) moorings near Point Conception, California, during April - July...

  19. Temperature profiles and current measurements from the Nathaniel B. Palmer during the 1997 Dovetail cruise in the Southern Ocean (NODC Accession 9900243)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data collection includes temperature profiles from CTD casts and current measurements from hull-mounted ADCP system aboard the research vessel Nathaniel B....

  20. Robust Current Control of Doubly Fed Wind Turbine Generator under Unbalanced Grid Voltage Conditions

    DEFF Research Database (Denmark)

    Wang, Yun; Gong, Wenming; Wu, Qiuwei

    2014-01-01

    This paper presents the design of a H ∞ current controller for doubly fed induction generators (DFIGs) in order to maintain stable operation under unbalanced voltage conditions. The H ∞ current controller has a multi-input and multi-output (MIMO) structure and is designed using the loop shaping...