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  • 1
    Online Resource
    Online Resource
    A Multiscale Approach to High-Resolution Ocean Profile Observations within a 4DVAR Analysis System
    American Meteorological Society ; 2019
    In:  Monthly Weather Review Vol. 147, No. 2 ( 2019-02-01), p. 627-643
    Details
    In: Monthly Weather Review, American Meteorological Society, Vol. 147, No. 2 ( 2019-02-01), p. 627-643
    Abstract: Most ocean data assimilation systems are tuned to process and assimilate observations to constrain features on the order of the mesoscale and larger. Typically this involves removal of observations or computing averaged observations. This procedure, while necessary, eliminates many observations from the analysis step and can reduce the overall effectiveness of a particular observing platform. Simply including these observations is not an option as doing so can produce an overdetermined, ill-conditioned problem that is more difficult to solve. An approach, presented here, aims to avoid such issues while at the same time increasing the number of observations within the assimilation. A two-step assimilation procedure with the four-dimensional variational data assimilation (4DVAR) system is adopted. The first step attempts to constrain the large-scale features by assimilating a set of super observations with appropriate background error correlation scales and error variances. The second step then attempts to correct smaller-scale features by assimilating the full observation set with shorter background error correlation scales and appropriate error variances; here the background state is taken as the analysis from the first step. Results using a real high-density observation set from underwater gliders in the region southeast of Iceland, collected during the 2017 Nordic Recognized Environmental Picture (NREP) experiment, will be shown using the Navy Coastal Ocean Model 4DVAR (NCOM-4DVAR).
    Type of Medium: Online Resource
    ISSN: 0027-0644 , 1520-0493
    URL: Article
    DOI: 10.1175/MWR-D-17-0300.1
    RVK:
    RA 1000
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2019
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    SSG: 14
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  • 2
    Online Resource
    Online Resource
    Late Holocene glacier expansion in the Cariboo and northern Rocky Mountains, British Columbia, Canada
    Elsevier BV ; 2012
    In:  Quaternary Science Reviews Vol. 51 ( 2012-9), p. 71-80
    Details
    In: Quaternary Science Reviews, Elsevier BV, Vol. 51 ( 2012-9), p. 71-80
    Type of Medium: Online Resource
    ISSN: 0277-3791
    URL: Article
    DOI: 10.1016/j.quascirev.2012.07.023
    RVK:
    RA 1000
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2012
    detail.hit.zdb_id: 780249-3
    detail.hit.zdb_id: 1495523-4
    SSG: 14
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  • 3
    Online Resource
    Online Resource
    Do Assimilated Drifter Velocities Improve Lagrangian Predictability in an Operational Ocean Model?
    American Meteorological Society ; 2015
    In:  Monthly Weather Review Vol. 143, No. 5 ( 2015-05-01), p. 1822-1832
    Details
    In: Monthly Weather Review, American Meteorological Society, Vol. 143, No. 5 ( 2015-05-01), p. 1822-1832
    Abstract: The Lagrangian predictability of general circulation models is limited by the need for high-resolution data streams to constrain small-scale dynamical features. Here velocity observations from Lagrangian drifters deployed in the Gulf of Mexico during the summer 2012 Grand Lagrangian Deployment (GLAD) experiment are assimilated into the Naval Coastal Ocean Model (NCOM) 4D variational (4DVAR) analysis system to examine their impact on Lagrangian predictability. NCOM-4DVAR is a weak-constraint assimilation system using the indirect representer method. Velocities derived from drifter trajectories, as well as satellite and in situ observations, are assimilated. Lagrangian forecast skill is assessed using separation distance and angular differences between simulated and observed trajectory positions. Results show that assimilating drifter velocities substantially improves the model forecast shape and position of a Loop Current ring. These gains in mesoscale Eulerian forecast skill also improve Lagrangian forecasts, reducing the growth rate of separation distances between observed and simulated drifters by approximately 7.3 km day−1 on average, when compared with forecasts that assimilate only temperature and salinity observations. Trajectory angular differences are also reduced.
    Type of Medium: Online Resource
    ISSN: 0027-0644 , 1520-0493
    URL: Article
    DOI: 10.1175/MWR-D-14-00164.1
    RVK:
    RA 1000
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2015
    detail.hit.zdb_id: 2033056-X
    detail.hit.zdb_id: 202616-8
    SSG: 14
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  • 4
    Online Resource
    Online Resource
    Examining the Potential Impact of SWOT Observations in an Ocean Analysis–Forecasting System
    American Meteorological Society ; 2016
    In:  Monthly Weather Review Vol. 144, No. 10 ( 2016-10), p. 3767-3782
    Details
    In: Monthly Weather Review, American Meteorological Society, Vol. 144, No. 10 ( 2016-10), p. 3767-3782
    Abstract: NASA’s Surface Water and Ocean Topography (SWOT) satellite, scheduled for launch in 2020, will provide observations of sea surface height anomaly (SSHA) at a significantly higher spatial resolution than current satellite altimeters. This new observation type is expected to improve the ocean model mesoscale circulation. The potential improvement that SWOT will provide is investigated in this work by way of twin-data assimilation experiments using the Navy Coastal Ocean Model four-dimensional variational data assimilation (NCOM-4DVAR) system in its weak constraint formulation. Simulated SWOT observations are sampled from an ocean model run (referred to as the “nature” run) using an observation-simulator program provided by the SWOT science team. The SWOT simulator provides realistic spatial coverage, resolution, and noise characteristics based on the expected performance of the actual satellite. Twin-data assimilation experiments are run for a two-month period during which simulated observations are assimilated into a separate model (known as the background model) in a series of 96-h windows. The final condition of each analysis window is used to initialize a new 96-h forecast, and each forecast is compared to the nature run to determine the impact of the assimilated data. It is demonstrated here that the simulated SWOT observations help to constrain the model mesoscale to be more consistent with the nature run than the assimilation of traditional altimeter observations alone. The findings of this study suggest that data from SWOT may have a substantial impact on improving the ocean model forecast of mesoscale features and surface ocean velocity.
    Type of Medium: Online Resource
    ISSN: 0027-0644 , 1520-0493
    URL: Article
    DOI: 10.1175/MWR-D-15-0361.1
    RVK:
    RA 1000
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2016
    detail.hit.zdb_id: 2033056-X
    detail.hit.zdb_id: 202616-8
    SSG: 14
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  • 5
    Online Resource
    Online Resource
    Impact of Assimilating Ocean Velocity Observations Inferred from Lagrangian Drifter Data Using the NCOM-4DVAR*
    American Meteorological Society ; 2014
    In:  Monthly Weather Review Vol. 142, No. 4 ( 2014-04-01), p. 1509-1524
    Details
    In: Monthly Weather Review, American Meteorological Society, Vol. 142, No. 4 ( 2014-04-01), p. 1509-1524
    Abstract: Eulerian velocity fields are derived from 300 drifters released in the Gulf of Mexico by The Consortium for Advanced Research on Transport of Hydrocarbon in the Environment (CARTHE) during the summer 2012 Grand Lagrangian Deployment (GLAD) experiment. These data are directly assimilated into the Navy Coastal Ocean Model (NCOM) four-dimensional variational data assimilation (4DVAR) analysis system in a series of experiments to investigate their impact on the model circulation. The NCOM-4DVAR is a newly developed tool for data analysis, formulated for weak-constraint data assimilation based on the indirect representer method. The assimilation experiments take advantage of this velocity data along with other available data sources from in situ and satellite measurements of surface and subsurface temperature and salinity. Three different experiments are done: (i) A nonassimilative NCOM free run, (ii) an assimilative NCOM run that utilizes temperature and salinity observations, and (iii) an assimilative NCOM run that uses temperature and salinity observations as well as the GLAD velocity observations. The resulting analyses and subsequent forecasts are compared to assimilated and future GLAD velocity and temperature/salinity observations to determine the performance of each experiment and the impact of the GLAD data on the analysis and the forecast. It is shown that the NCOM-4DVAR is able to fit the observations not only in the analysis step, but also in the subsequent forecast. It is also found that the GLAD velocity data greatly improves the characterization of the circulation, with the forecast showing a better fit to future GLAD observations than those experiments without the velocity data included.
    Type of Medium: Online Resource
    ISSN: 0027-0644 , 1520-0493
    URL: Article
    DOI: 10.1175/MWR-D-13-00236.1
    RVK:
    RA 1000
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2014
    detail.hit.zdb_id: 2033056-X
    detail.hit.zdb_id: 202616-8
    SSG: 14
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  • 6
    Online Resource
    Online Resource
    Impact of Assimilating Surface Velocity Observations on the Model Sea Surface Height Using the NCOM-4DVAR*
    American Meteorological Society ; 2016
    In:  Monthly Weather Review Vol. 144, No. 3 ( 2016-03-01), p. 1051-1068
    Details
    In: Monthly Weather Review, American Meteorological Society, Vol. 144, No. 3 ( 2016-03-01), p. 1051-1068
    Abstract: The assimilation of surface velocity observations and their impact on the model sea surface height (SSH) is examined using an operational regional ocean model and its four-dimensional variational data assimilation (4DVAR) analysis component. In this work, drifter-derived surface velocity observations are assimilated into the Navy’s Coastal Ocean Model (NCOM) 4DVAR in weak-constraint mode for a Gulf of Mexico (GoM) experiment during August–September 2012. During this period the model is trained by assimilating surface velocity observations (in a series of 96-h assimilation windows), which is followed by a 30-day forecast through the month of October 2012. A free-run model and a model that assimilates along-track SSH observations are also run as baseline experiments to which the other experiments are compared. It is shown here that the assimilation of surface velocity measurements has a substantial impact on improving the model representation of the forecast SSH on par with the experiment that assimilates along-track SSH observations directly. Finally, an assimilation experiment is done where both along-track SSH and velocity observations are utilized in an attempt to determine if the observation types are redundant or complementary. It is found that the combination of observations provides the best SSH forecast, in terms of the fit to observations, when compared to the previous experiments.
    Type of Medium: Online Resource
    ISSN: 0027-0644 , 1520-0493
    URL: Article
    DOI: 10.1175/MWR-D-14-00285.1
    RVK:
    RA 1000
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2016
    detail.hit.zdb_id: 2033056-X
    detail.hit.zdb_id: 202616-8
    SSG: 14
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  • 7
    Online Resource
    Online Resource
    Seabird assemblages are linked to the major western boundary current off eastern Australia
    Elsevier BV ; 2024
    In:  Progress in Oceanography Vol. 223 ( 2024-04), p. 103215-
    Details
    In: Progress in Oceanography, Elsevier BV, Vol. 223 ( 2024-04), p. 103215-
    Type of Medium: Online Resource
    ISSN: 0079-6611
    URL: Article
    DOI: 10.1016/j.pocean.2024.103215
    RVK:
    RB 10402
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2024
    detail.hit.zdb_id: 1497436-8
    detail.hit.zdb_id: 4062-9
    SSG: 21,3
    SSG: 14
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  • 8
    Online Resource
    Online Resource
    Micro- and macronutrients in the southeastern Bering Sea: Insight into iron-replete and iron-depleted regimes
    Elsevier BV ; 2007
    In:  Progress in Oceanography Vol. 73, No. 2 ( 2007-5), p. 99-126
    Details
    In: Progress in Oceanography, Elsevier BV, Vol. 73, No. 2 ( 2007-5), p. 99-126
    Type of Medium: Online Resource
    ISSN: 0079-6611
    URL: Article
    DOI: 10.1016/j.pocean.2006.12.002
    RVK:
    RB 10402
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2007
    detail.hit.zdb_id: 1497436-8
    detail.hit.zdb_id: 4062-9
    SSG: 21,3
    SSG: 14
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  • 9
    Online Resource
    Online Resource
    Recent multivariate changes in the North Atlantic climate system, with a focus on 2005–2016
    Wiley ; 2018
    In:  International Journal of Climatology Vol. 38, No. 14 ( 2018-11), p. 5050-5076
    Details
    In: International Journal of Climatology, Wiley, Vol. 38, No. 14 ( 2018-11), p. 5050-5076
    Abstract: Major changes are occurring across the North Atlantic climate system, including in the atmosphere, ocean and cryosphere, and many observed changes are unprecedented in instrumental records. As the changes in the North Atlantic directly affect the climate and air quality of the surrounding continents, it is important to fully understand how and why the changes are taking place, not least to predict how the region will change in the future. To this end, this article characterizes the recent observed changes in the North Atlantic region, especially in the period 2005–2016, across many different aspects of the system including: atmospheric circulation; atmospheric composition; clouds and aerosols; ocean circulation and properties; and the cryosphere. Recent changes include: an increase in the speed of the North Atlantic jet stream in winter; a southward shift in the North Atlantic jet stream in summer, associated with a weakening summer North Atlantic Oscillation; increases in ozone and methane; increases in net absorbed radiation in the mid‐latitude western Atlantic, linked to an increase in the abundance of high level clouds and a reduction in low level clouds; cooling of sea surface temperatures in the North Atlantic subpolar gyre, concomitant with increases in the western subtropical gyre, and a decline in the Atlantic Ocean's overturning circulation; a decline in Atlantic sector Arctic sea ice and rapid melting of the Greenland Ice Sheet. There are many interactions between these changes, but these interactions are poorly understood. This article concludes by highlighting some of the key outstanding questions.
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Issue
    URL: Article
    DOI: 10.1002/joc.2018.38.issue-14
    DOI: 10.1002/joc.5815
    RVK:
    RA 1000
    Language: English
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 1491204-1
    SSG: 14
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