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  • 11
    Online Resource
    Online Resource
    Forecast skill score assessment of a relocatable ocean prediction system, using a simplified objective analysis method
    Copernicus GmbH ; 2017
    In:  Ocean Science Vol. 13, No. 6 ( 2017-11-20), p. 925-945
    Details
    In: Ocean Science, Copernicus GmbH, Vol. 13, No. 6 ( 2017-11-20), p. 925-945
    Abstract: Abstract. A relocatable ocean prediction system (ROPS) was employed to an observational data set which was collected in June 2014 in the waters to the west of Sardinia (western Mediterranean) in the framework of the REP14-MED experiment. The observational data, comprising more than 6000 temperature and salinity profiles from a fleet of underwater gliders and shipborne probes, were assimilated in the Regional Ocean Modeling System (ROMS), which is the heart of ROPS, and verified against independent observations from ScanFish tows by means of the forecast skill score as defined by Murphy(1993). A simplified objective analysis (OA) method was utilised for assimilation, taking account of only those profiles which were located within a predetermined time window W. As a result of a sensitivity study, the highest skill score was obtained for a correlation length scale C = 12.5 km, W = 24 h, and r = 1, where r is the ratio between the error of the observations and the background error, both for temperature and salinity. Additional ROPS runs showed that (i) the skill score of assimilation runs was mostly higher than the score of a control run without assimilation, (i) the skill score increased with increasing forecast range, and (iii) the skill score for temperature was higher than the score for salinity in the majority of cases. Further on, it is demonstrated that the vast number of observations can be managed by the applied OA method without data reduction, enabling timely operational forecasts even on a commercially available personal computer or a laptop.
    Type of Medium: Online Resource
    ISSN: 1812-0792
    URL: Article
    DOI: 10.5194/os-13-925-2017
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2017
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  • 12
    Online Resource
    Online Resource
    Assistant systems for aircraft guidance: cognitive man-machine cooperation
    Elsevier BV ; 2001
    In:  Aerospace Science and Technology Vol. 5, No. 8 ( 2001-12), p. 511-520
    Details
    In: Aerospace Science and Technology, Elsevier BV, Vol. 5, No. 8 ( 2001-12), p. 511-520
    Type of Medium: Online Resource
    ISSN: 1270-9638
    URL: Article
    DOI: 10.1016/S1270-9638(01)01137-3
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2001
    detail.hit.zdb_id: 2014638-3
    SSG: 16,12
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  • 13
    Online Resource
    Online Resource
    A Model of Baroclinic Instability and Waves between the Ventilated Gyre and the Shadow Zone of the North Atlantic Ocean
    American Meteorological Society ; 1991
    In:  Journal of Physical Oceanography Vol. 21, No. 1 ( 1991-01), p. 53-67
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 21, No. 1 ( 1991-01), p. 53-67
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/1520-0485(1991)021〈0053:AMOBIA〉2.0.CO;2
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 1991
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    detail.hit.zdb_id: 184162-2
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  • 14
    Online Resource
    Online Resource
    Human factors in the guidance of uninhabited vehicles: oxymoron or tautology? : The potential of cognitive and co-operative automation
    Springer Science and Business Media LLC ; 2009
    In:  Cognition, Technology & Work Vol. 11, No. 1 ( 2009-2), p. 71-86
    Details
    In: Cognition, Technology & Work, Springer Science and Business Media LLC, Vol. 11, No. 1 ( 2009-2), p. 71-86
    Type of Medium: Online Resource
    ISSN: 1435-5558 , 1435-5566
    URL: Article
    DOI: 10.1007/s10111-008-0123-2
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2009
    detail.hit.zdb_id: 1499110-X
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  • 15
    Online Resource
    Online Resource
    The Creation of Reveresed Baroclinicity and Subsurfaces Jets in Oceanic Eddies
    American Meteorological Society ; 1990
    In:  Journal of Physical Oceanography Vol. 20, No. 5 ( 1990-05), p. 786-791
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 20, No. 5 ( 1990-05), p. 786-791
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/1520-0485(1990)020〈0786:TCORBA〉2.0.CO;2
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 1990
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    detail.hit.zdb_id: 184162-2
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  • 16
    Online Resource
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    A hybrid variational-ensemble data assimilation scheme with systematic error correction for limited-area ocean models
    Copernicus GmbH ; 2016
    In:  Ocean Science Vol. 12, No. 5 ( 2016-10-14), p. 1137-1153
    Details
    In: Ocean Science, Copernicus GmbH, Vol. 12, No. 5 ( 2016-10-14), p. 1137-1153
    Abstract: Abstract. A hybrid variational-ensemble data assimilation scheme to estimate the vertical and horizontal parts of the background error covariance matrix for an ocean variational data assimilation system is presented and tested in a limited-area ocean model implemented in the western Mediterranean Sea. An extensive data set collected during the Recognized Environmental Picture Experiments conducted in June 2014 by the Centre for Maritime Research and Experimentation has been used for assimilation and validation. The hybrid scheme is used to both correct the systematic error introduced in the system from the external forcing (initialisation, lateral and surface open boundary conditions) and model parameterisation, and improve the representation of small-scale errors in the background error covariance matrix. An ensemble system is run offline for further use in the hybrid scheme, generated through perturbation of assimilated observations. Results of four different experiments have been compared. The reference experiment uses the classical stationary formulation of the background error covariance matrix and has no systematic error correction. The other three experiments account for, or not, systematic error correction and hybrid background error covariance matrix combining the static and the ensemble-derived errors of the day. Results show that the hybrid scheme when used in conjunction with the systematic error correction reduces the mean absolute error of temperature and salinity misfit by 55 and 42 % respectively, versus statistics arising from standard climatological covariances without systematic error correction.
    Type of Medium: Online Resource
    ISSN: 1812-0792
    URL: Article
    DOI: 10.5194/os-12-1137-2016
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2016
    detail.hit.zdb_id: 2183769-7
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  • 17
    Online Resource
    Online Resource
    Validation of an ocean shelf model for the prediction of mixed-layer properties in the Mediterranean Sea west of Sardinia
    Copernicus GmbH ; 2017
    In:  Ocean Science Vol. 13, No. 2 ( 2017-04-03), p. 235-257
    Details
    In: Ocean Science, Copernicus GmbH, Vol. 13, No. 2 ( 2017-04-03), p. 235-257
    Abstract: Abstract. The Regional Ocean Modeling System (ROMS) has been employed to explore the sensitivity of the forecast skill of mixed-layer properties to initial conditions, boundary conditions, and vertical mixing parameterisations. The initial and lateral boundary conditions were provided by the Mediterranean Forecasting System (MFS) or by the MERCATOR global ocean circulation model via one-way nesting; the initial conditions were additionally updated through the assimilation of observations. Nowcasts and forecasts from the weather forecast models COSMO-ME and COSMO-IT, partly melded with observations, served as surface boundary conditions. The vertical mixing was parameterised by the GLS (generic length scale) scheme Umlauf and Burchard (2003) in four different set-ups. All ROMS forecasts were validated against the observations which were taken during the REP14-MED survey to the west of Sardinia. Nesting ROMS in MERCATOR and updating the initial conditions through data assimilation provided the best agreement of the predicted mixed-layer properties with the time series from a moored thermistor chain. Further improvement was obtained by the usage of COSMO-ME atmospheric forcing, which was melded with real observations, and by the application of the k-ω vertical mixing scheme with increased vertical eddy diffusivity. The predicted temporal variability of the mixed-layer temperature was reasonably well correlated with the observed variability, while the modelled variability of the mixed-layer depth exhibited only agreement with the observations near the diurnal frequency peak. For the forecasted horizontal variability, reasonable agreement was found with observations from a ScanFish section, but only for the mesoscale wave number band; the observed sub-mesoscale variability was not reproduced by ROMS.
    Type of Medium: Online Resource
    ISSN: 1812-0792
    URL: Article
    DOI: 10.5194/os-13-235-2017
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2017
    detail.hit.zdb_id: 2183769-7
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  • 18
    Online Resource
    Online Resource
    Measuring pH variability using an experimental sensor on an underwater glider
    Copernicus GmbH ; 2017
    In:  Ocean Science Vol. 13, No. 3 ( 2017-05-24), p. 427-442
    Details
    In: Ocean Science, Copernicus GmbH, Vol. 13, No. 3 ( 2017-05-24), p. 427-442
    Abstract: Abstract. Autonomous underwater gliders offer the capability of measuring oceanic parameters continuously at high resolution in both vertical and horizontal planes, with timescales that can extend to many months. An experimental ion-sensitive field-effect transistor (ISFET) sensor measuring pH on the total scale was attached to a glider during the REP14-MED experiment in June 2014 in the Sardinian Sea in the northwestern Mediterranean. During the deployment, pH was sampled at depths of up to 1000 m along an 80 km transect over a period of 12 days. Water samples were collected from a nearby ship and analysed for dissolved inorganic carbon concentration and total alkalinity to derive the pH for validating the ISFET sensor measurements. The vertical resolution of the pH sensor was good (1 to 2 m), but stability was poor and the sensor drifted in a non-monotonous fashion. In order to remove the sensor drift, a depth-constant time-varying offset was applied throughout the water column for each dive, reducing the spread of the data by approximately two-thirds. Furthermore, the ISFET sensor required temperature- and pressure-based corrections, which were achieved using linear regression. Correcting for this decreased the apparent sensor pH variability by a further 13 to 31 %. Sunlight caused an apparent sensor pH decrease of up to 0.1 in surface waters around local noon, highlighting the importance of shielding the sensor from light in future deployments. The corrected pH from the ISFET sensor is presented along with potential temperature, salinity, potential density anomalies (σθ), and dissolved oxygen concentrations (c(O2)) measured by the glider, providing insights into the physical and biogeochemical variability in the Sardinian Sea. The pH maxima were identified close to the depth of the summer chlorophyll maximum, where high c(O2) values were also found. Longitudinal pH variations at depth (σθ 〉 28. 8 kg m−3) highlighted the variability of water masses in the Sardinian Sea. Higher pH was observed where salinity was  〉 38. 65, and lower pH was found where salinity ranged between 38.3 and 38.65. The higher pH was associated with saltier Levantine Intermediate Water, and it is possible that the lower pH was related to the remineralisation of organic matter. Furthermore, shoaling isopycnals closer to shore coinciding with low pH and c(O2), high salinity, alkalinity, dissolved inorganic carbon concentrations, and chlorophyll fluorescence waters may be indicative of upwelling.
    Type of Medium: Online Resource
    ISSN: 1812-0792
    URL: Article
    DOI: 10.5194/os-13-427-2017
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2017
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  • 19
    Online Resource
    Online Resource
    High-resolution observations in the western Mediterranean Sea: the REP14-MED experiment
    Copernicus GmbH ; 2018
    In:  Ocean Science Vol. 14, No. 2 ( 2018-04-26), p. 321-335
    Details
    In: Ocean Science, Copernicus GmbH, Vol. 14, No. 2 ( 2018-04-26), p. 321-335
    Abstract: Abstract. The observational part of the REP14-MED experiment was conducted in June 2014 in the Sardo-Balearic Basin west of Sardinia (western Mediterranean Sea). Two research vessels collected high-resolution oceanographic data by means of hydrographic casts, towed systems, and underway measurements. In addition, a vast amount of data was provided by a fleet of 11 ocean gliders, time series were available from moored instruments, and information on Lagrangian flow patterns was obtained from surface drifters and one profiling float. The spatial resolution of the observations encompasses a spectrum over 4 orders of magnitude from 𝒪(101 m) to 𝒪(105 m), and the time series from the moored instruments cover a spectral range of 5 orders from 𝒪(101 s) to 𝒪(106 s). The objective of this article is to provide an overview of the huge data set which has been utilised by various studies, focusing on (i) water masses and circulation, (ii) operational forecasting, (iii) data assimilation, (iv) variability of the ocean, and (v) new payloads for gliders.
    Type of Medium: Online Resource
    ISSN: 1812-0792
    URL: Article
    DOI: 10.5194/os-14-321-2018
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2018
    detail.hit.zdb_id: 2183769-7
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  • 20
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    Seasonal variability of flow instabilities in the Strait of Sicily
    American Geophysical Union (AGU) ; 1998
    In:  Journal of Geophysical Research: Oceans Vol. 103, No. C11 ( 1998-10-15), p. 24799-24820
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 103, No. C11 ( 1998-10-15), p. 24799-24820
    Abstract: The eastern and western Mediterranean Seas are connected by the Strait of Sicily. The mean flow conditions comprise a near‐surface flow of Atlantic Water (AW) into the eastern Mediterranean and an outflow of Levantine Intermediate Water (LIW) below. We present results of a numerical model investigating the stability of currents in the Strait. The model is nonlinear and uses a hybrid (quasi‐isopycnic) vertical coordinate. The model domain is a periodic channel with horizontal dimensions of 400 × 200 km and different bathymetries. As initial conditions, we use seasonal climatological density fields varying only in cross‐channel direction. External forcing is not applied. Combining three different bathymetries with both summer and winter climatological data, we show the results of six model integrations. In all cases the flow is baroclinically unstable, the most unstable waves being 100 and 133 km wavelength in summer and 67 km in winter. A cross‐channel parabolic bottom profile instead of a flat bottom stabilizes the flow in the north (on the Sicilian side of the Strait) but causes further destabilization in the south (on the African side). Further modification of the bathymetry in terms of shallow shelf sea areas to the south of Sicily leads to a deflection of the summer flow in both the AW and the LIW range and to the generation of stationary eddies. In agreement with observations the final kinetic and eddy kinetic energies of the model are higher in winter than in summer in all model runs. From an inspection of satellite images, evidence was found for unstable waves of similar wavelength as predicted by the model. Records from moored current meters support enhanced flow instability on the African side of the Strait. The position and circulation sense of the stationary eddies in the AW range are found to be consistent with climatology and previously known patches of low sea surface temperature.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/98JC00891
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1998
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    SSG: 16,13
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