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  • 1
    Online-Ressource
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    American Meteorological Society ; 2012
    In:  Journal of Atmospheric and Oceanic Technology Vol. 29, No. 9 ( 2012-09-01), p. 1377-1390
    In: Journal of Atmospheric and Oceanic Technology, American Meteorological Society, Vol. 29, No. 9 ( 2012-09-01), p. 1377-1390
    Kurzfassung: Estimates of surface currents over the continental shelf are now regularly made using high-frequency radar (HFR) systems along much of the U.S. coastline. The recently deployed HFR system at the Martha’s Vineyard Coastal Observatory (MVCO) is a unique addition to these systems, focusing on high spatial resolution over a relatively small coastal ocean domain with high accuracy. However, initial results from the system showed sizable errors and biased estimates of M2 tidal currents, prompting an examination of new methods to improve the quality of radar-based velocity data. The analysis described here utilizes the radial metric output of CODAR Ocean Systems’ version 7 release of the SeaSonde Radial Site Software Suite to examine both the characteristics of the received signal and the output of the direction-finding algorithm to provide data quality controls on the estimated radial currents that are independent of the estimated velocity. Additionally, the effect of weighting spatial averages of radials falling within the same range and azimuthal bin is examined to account for differences in signal quality. Applied to two month-long datasets from the MVCO high-resolution system, these new methods are found to improve the rms difference comparisons with in situ current measurements by up to 2 cm s−1, as well as reduce or eliminate observed biases of tidal ellipses estimated using standard methods.
    Materialart: Online-Ressource
    ISSN: 0739-0572 , 1520-0426
    Sprache: Englisch
    Verlag: American Meteorological Society
    Publikationsdatum: 2012
    ZDB Id: 2021720-1
    ZDB Id: 48441-6
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    Online-Ressource
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    American Meteorological Society ; 2009
    In:  Journal of Physical Oceanography Vol. 39, No. 11 ( 2009-11-01), p. 2942-2956
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 39, No. 11 ( 2009-11-01), p. 2942-2956
    Kurzfassung: Recent work by S. Lentz et al. documents offshore transport in the inner shelf due to a wave-driven return flow associated with the Hasselmann wave stress (the Stokes–Coriolis force). This analysis is extended using observations from the central Oregon coast to identify the wave-driven return flow present and quantify the potential bias of wind-driven across-shelf exchange by unresolved wave-driven circulation. Using acoustic Doppler current profiler (ADCP) measurements at six stations, each in water depths of 13–15 m, observed depth-averaged, across-shelf velocities were generally correlated with theoretical estimates of the proposed return flow. During times of minimal wind forcing, across-shelf velocity profiles were vertically sheared, with stronger velocities near the top of the measured portion of the water column, and increased in magnitude with increasing significant wave height, consistent with circulation due to the Hasselmann wave stress. Yet velocity magnitudes and vertical shears were stronger than that predicted by linear wave theory, and more similar to the stratified “summer” velocity profiles described by S. Lentz et al. Additionally, substantial temporal and spatial variability of the wave-driven return flow was found, potentially due to changing wind and wave conditions as well as local bathymetric variability. Despite the wave-driven circulation found, subtracting estimates of the return flow from the observed across-shelf velocity had no significant effect on estimates of the across-shelf exchange due to along-shelf wind forcing at these water depths along the Oregon coast during summer.
    Materialart: Online-Ressource
    ISSN: 1520-0485 , 0022-3670
    Sprache: Englisch
    Verlag: American Meteorological Society
    Publikationsdatum: 2009
    ZDB Id: 2042184-9
    ZDB Id: 184162-2
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
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    American Meteorological Society ; 2022
    In:  Journal of Atmospheric and Oceanic Technology Vol. 39, No. 2 ( 2022-02), p. 223-235
    In: Journal of Atmospheric and Oceanic Technology, American Meteorological Society, Vol. 39, No. 2 ( 2022-02), p. 223-235
    Kurzfassung: Previous work with simulations of oceanographic high-frequency (HF) radars has identified possible improvements when using maximum likelihood estimation (MLE) for direction of arrival; however, methods for determining the number of emitters (here defined as spatially distinct patches of the ocean surface) have not realized these improvements. Here we describe and evaluate the use of the likelihood ratio (LR) for emitter detection, demonstrating its application to oceanographic HF radar data. The combined detection–estimation methods MLE-LR are compared with multiple signal classification method (MUSIC) and MUSIC parameters for SeaSonde HF radars, along with a method developed for 8-channel systems known as MUSIC-Highest. Results show that the use of MLE-LR produces similar accuracy, in terms of the RMS difference and correlation coefficients squared, as previous methods. We demonstrate that improved accuracy can be obtained for both methods, at the cost of fewer velocity observations and decreased spatial coverage. For SeaSondes, accuracy improvements are obtained with less commonly used parameter sets. The MLE-LR is shown to be able to resolve simultaneous closely spaced emitters, which has the potential to improve observations obtained by HF radars operating in complex current environments. Significance Statement We identify and test a method based on the likelihood ratio (LR) for determining the number of signal sources in observations subject to direction finding with maximum likelihood estimation (MLE). Direction-finding methods are used in broad-ranging applications that include radar, sonar, and wireless communication. Previous work suggests accuracy improvements when using MLE, but suitable methods for determining the number of simultaneous signal sources are not well known. Our work shows that the LR, when combined with MLE, performs at least as well as alternative methods when applied to oceanographic high-frequency (HF) radars. In some situations, MLE and LR obtain superior resolution, where resolution is defined as the ability to distinguish closely spaced signal sources.
    Materialart: Online-Ressource
    ISSN: 0739-0572 , 1520-0426
    Sprache: Unbekannt
    Verlag: American Meteorological Society
    Publikationsdatum: 2022
    ZDB Id: 2021720-1
    ZDB Id: 48441-6
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
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    American Geophysical Union (AGU) ; 2019
    In:  Journal of Geophysical Research: Oceans Vol. 124, No. 1 ( 2019-01), p. 593-614
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 124, No. 1 ( 2019-01), p. 593-614
    Kurzfassung: Subsurface fronts are generated by the interaction of tides, stratification, and shallow bathymetry Fiber‐optic bottom temperature sensing detects propagation of subsurface fronts Characteristics of high‐frequency temperature variability vary dramatically over short alongshore scales
    Materialart: Online-Ressource
    ISSN: 2169-9275 , 2169-9291
    Sprache: Englisch
    Verlag: American Geophysical Union (AGU)
    Publikationsdatum: 2019
    ZDB Id: 2016804-4
    ZDB Id: 161667-5
    ZDB Id: 3094219-6
    SSG: 16,13
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 5
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    American Geophysical Union (AGU) ; 2020
    In:  Journal of Geophysical Research: Oceans Vol. 125, No. 5 ( 2020-05)
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 125, No. 5 ( 2020-05)
    Kurzfassung: Recirculation flow is induced, shedding submesoscale cyclonic eddies Headland eddy generation is influenced by the Kuroshio and tidal flows Eddies corotate and merge further downstream
    Materialart: Online-Ressource
    ISSN: 2169-9275 , 2169-9291
    Sprache: Englisch
    Verlag: American Geophysical Union (AGU)
    Publikationsdatum: 2020
    ZDB Id: 2016804-4
    ZDB Id: 161667-5
    ZDB Id: 3094219-6
    SSG: 16,13
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 6
    Online-Ressource
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    American Geophysical Union (AGU) ; 2005
    In:  Journal of Geophysical Research Vol. 110, No. C10 ( 2005)
    In: Journal of Geophysical Research, American Geophysical Union (AGU), Vol. 110, No. C10 ( 2005)
    Materialart: Online-Ressource
    ISSN: 0148-0227
    Sprache: Englisch
    Verlag: American Geophysical Union (AGU)
    Publikationsdatum: 2005
    ZDB Id: 2033040-6
    ZDB Id: 3094104-0
    ZDB Id: 2130824-X
    ZDB Id: 2016813-5
    ZDB Id: 2016810-X
    ZDB Id: 2403298-0
    ZDB Id: 2016800-7
    ZDB Id: 161666-3
    ZDB Id: 161667-5
    ZDB Id: 2969341-X
    ZDB Id: 161665-1
    ZDB Id: 3094268-8
    ZDB Id: 710256-2
    ZDB Id: 2016804-4
    ZDB Id: 3094181-7
    ZDB Id: 3094219-6
    ZDB Id: 3094167-2
    ZDB Id: 2220777-6
    ZDB Id: 3094197-0
    SSG: 16,13
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 7
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    Elsevier BV ; 2021
    In:  Continental Shelf Research Vol. 230 ( 2021-11), p. 104567-
    In: Continental Shelf Research, Elsevier BV, Vol. 230 ( 2021-11), p. 104567-
    Materialart: Online-Ressource
    ISSN: 0278-4343
    Sprache: Englisch
    Verlag: Elsevier BV
    Publikationsdatum: 2021
    ZDB Id: 2025704-1
    ZDB Id: 780256-0
    SSG: 13
    SSG: 14
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 8
    Online-Ressource
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    IOP Publishing ; 2020
    In:  Journal of Physics: Conference Series Vol. 1452, No. 1 ( 2020-01-01), p. 012028-
    In: Journal of Physics: Conference Series, IOP Publishing, Vol. 1452, No. 1 ( 2020-01-01), p. 012028-
    Kurzfassung: There is an acute need for a long-term metocean reference site that will aid the near-term development of the offshore wind energy industry in the United States. High quality, multi-year observations of the wind resource at hub height in areas relevant to offshore wind energy are a requirement for reducing uncertainties in wind resource assessment, improving the fidelity of numerical models, assimilated products of the resource, and forecasts of near-term operational conditions and wind energy power production. Yet, few long-term data sets exist over the U.S. outer continental shelf that can provide accurate guidance for developers, turbine manufacturers, and utility operators. Thus, there is a critical need for robust, long-term data collection at a site having conditions representative of wind energy development areas. Additionally, an efficient and effective location for validating existing measurement systems and testing and verifying the accuracy of new sensors will play a key role in reducing uncertainty of estimates of the wind resource and reducing the cost and risk associated with offshore development.
    Materialart: Online-Ressource
    ISSN: 1742-6588 , 1742-6596
    Sprache: Unbekannt
    Verlag: IOP Publishing
    Publikationsdatum: 2020
    ZDB Id: 2166409-2
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 9
    Online-Ressource
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    Oxford University Press (OUP) ; 2009
    In:  ICES Journal of Marine Science Vol. 66, No. 2 ( 2009-03-01), p. 396-407
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 66, No. 2 ( 2009-03-01), p. 396-407
    Kurzfassung: Dudas, S. E., Grantham, B. A., Kirincich, A. R., Menge, B. A., Lubchenco, J., and Barth, J. A. 2009. Current reversals as determinants of intertidal recruitment on the central Oregon coast. – ICES Journal of Marine Science, 66: 396–407. The influence of current reversals on intertidal invertebrate recruitment was investigated using two seasons of nearshore physical and intertidal biological observations along the central Oregon coast, an intermittent upwelling system. In 1998, upwelling periods were punctuated by infrequent wind reversals and widespread increases in nearshore temperature, whereas 1999 was characterized by frequent, shorter wind reversals. In 1998, barnacle recruitment was best at the site experiencing more frequent reversals of the predominantly equatorward currents, higher poleward velocities, and coincident temperature increases. In 1999, barnacle recruitment peaked at the site with greater poleward current velocities, and maximum mussel recruitment at the site with consistent deep (10 m) onshore currents. Barnacle recruitment generally increased with onshore surface currents and temperature; mussel recruitment showed variable, weaker correlations. The data indicate that substantial decreases or complete reversals of upwelling-driven alongshore currents may be important for barnacle recruitment, but topographically driven differences in the response of currents to wind changes may generate local recruitment differences. This suggests that even relatively straight coastlines may have enhanced recruitment zones attributable to the variable local oceanography. Further, the interannual differences observed in current reversals and recruitment patterns highlight the potential importance of upwelling variation for onshore communities.
    Materialart: Online-Ressource
    ISSN: 1095-9289 , 1054-3139
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2009
    ZDB Id: 2463178-4
    ZDB Id: 1468003-8
    ZDB Id: 29056-7
    SSG: 12
    SSG: 21,3
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 10
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    Marine Technology Society ; 2013
    In:  Marine Technology Society Journal Vol. 47, No. 4 ( 2013-07-01), p. 206-217
    In: Marine Technology Society Journal, Marine Technology Society, Vol. 47, No. 4 ( 2013-07-01), p. 206-217
    Kurzfassung: Abstract There is now a large installed base of high-frequency (HF) coastal ocean radars in the United States able to measure surface currents on an operational basis. However, these instruments also have the potential to provide estimates of the spatially variable surface wind field over distances ranging from 10 to 200 km offshore. This study investigates the ability of direction-finding HF radars to recover spatial maps of wind speed and direction from the dominant first-order region radar returns using empirical models. Observations of radar backscatter from the Martha’s Vineyard Coastal Observatory HF radar system were compared to wind observations from an offshore tower, finding significant correlations between wind speed and the backscatter power for a range of angles between the wind and radar loop directions. Models for the directional spreading of wind waves were analyzed in comparison to data-based results, finding potentially significant differences between the model and data-based spreading relationships. Using empirical fits, radar-based estimates of wind speed and direction at the location of the in situ wind sensor had error rates of 2 m/s and 60°, which decreased with hourly averaging. Attempts to extrapolate the results to the larger domain illustrated that spatially dependent transfer functions for wind speed and direction appear possible for large coastal ocean domains based on a small number of temporary, or potentially mobile, in situ wind sensors.
    Materialart: Online-Ressource
    ISSN: 0025-3324
    Sprache: Englisch
    Verlag: Marine Technology Society
    Publikationsdatum: 2013
    ZDB Id: 410693-3
    ZDB Id: 2730536-3
    Standort Signatur Einschränkungen Verfügbarkeit
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