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  • 1
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    Online Resource
    Assimilation studies of open‐ocean flows: 2. Error measures with strongly nonlinear dynamics
    American Geophysical Union (AGU) ; 1996
    In:  Journal of Geophysical Research: Oceans Vol. 101, No. C12 ( 1996-12-15), p. 28473-28488
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 101, No. C12 ( 1996-12-15), p. 28473-28488
    Abstract: In a companion paper by Gunson and Malanotte‐Rizzoli [this issue], the problem of estimating boundary and initial conditions for a regional open‐ocean model from sparse data is addressed using the adjoint method. Here the estimation of error covariances for the estimated boundary and initial conditions and interior fields, in the presence of strongly nonlinear dynamics, is investigated. The evaluation of the full error covariance matrix for the estimated control variables from the inverse Hessian matrix is presented along with its dependence upon the degree of nonlinearity in the dynamics. Major new results here obtained are the availability of off‐diagonal covariances, the successful calculation of error covariances for all boundary and initial conditions, and the estimation of errors for interior fields. The role of the Hessian matrix is assessed in gauging the sensitivity of the estimated boundary and initial conditions to the data.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/96JC02780
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1996
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  • 2
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    A new mechanism for the generation of quasi-zonal jets in the ocean : QUASI-ZONAL JETS IN THE OCEAN
    American Geophysical Union (AGU) ; 2012
    In:  Geophysical Research Letters Vol. 39, No. 10 ( 2012-05-28), p. n/a-n/a
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 39, No. 10 ( 2012-05-28), p. n/a-n/a
    Type of Medium: Online Resource
    ISSN: 0094-8276
    URL: Article
    DOI: 10.1029/2012GL051861
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2012
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  • 3
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    Principles of Ocean Physics
    American Geophysical Union (AGU) ; 1989
    In:  Eos, Transactions American Geophysical Union Vol. 70, No. 1 ( 1989-01-03), p. 4-4
    Details
    In: Eos, Transactions American Geophysical Union, American Geophysical Union (AGU), Vol. 70, No. 1 ( 1989-01-03), p. 4-4
    Abstract: This book is an excellent textbook for an undergraduate course in physical oceanography, and some of its chapters can also be used in a graduate introductory course. The book is clearly written from the perspective of a physicist, as the title itself declares. Therefore, it gives a different and interesting approach to physical oceanography, complementary to that of the vast majority of introductory textbooks, which are much more descriptive and phenomenologically oriented. After the introduction, with an historical review of the evolution of physical oceanography, Chapter 2 is devoted to a review of t he major forces driving the ocean's general circulation. This chapter contains well‐organized and clear discussions of radiative forcing a nd of the basics of atmospheric circulation and the ocean response, both for wind‐driven and thermohaline components of the circulation, on the global scale. This chapter also offers an informative section on the sea floor and its dynamics, thus enclosing the oceanic layer between its two natural boundaries, the atmosphere above and the ocean floor below.
    Type of Medium: Online Resource
    ISSN: 0096-3941 , 2324-9250
    URL: Article
    DOI: 10.1029/89EO00003
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1989
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  • 4
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    Open‐ocean boundary conditions from interior data: Local and remote forcing of Massachusetts Bay
    American Geophysical Union (AGU) ; 1996
    In:  Journal of Geophysical Research: Oceans Vol. 101, No. C3 ( 1996-03-15), p. 6487-6500
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 101, No. C3 ( 1996-03-15), p. 6487-6500
    Abstract: Massachusetts and Cape Cod Bays form a semienclosed coastal basin that opens onto the much larger Gulf of Maine. Subtidal circulation in the bay is driven by local winds and remotely driven flows from the gulf. The local‐wind forced flow is estimated with a regional shallow water model driven by wind measurements. The model uses a gravity wave radiation condition along the open‐ocean boundary. Results compare reasonably well with observed currents near the coast. In some offshore regions, however, modeled flows are an order of magnitude less energetic than the data. Strong flows are observed even during periods of weak local wind forcing. Poor model‐data comparisons are attributable, at least in part, to open‐ocean boundary conditions that neglect the effects of remote forcing. Velocity measurements from within Massachusetts Bay are used to estimate the remotely forced component of the flow. The data are combined with shallow water dynamics in an inverse‐model formulation that follows the theory of Bennett and McIntosh [1982], who considered tides. We extend their analysis to consider the subtidal response to transient forcing. The inverse model adjusts the a priori open‐ocean boundary condition, thereby minimizing a combined measure of model‐data misfit and boundary condition adjustment. A “consistency criterion” determines the optimal trade‐off between the two. The criterion is based on a measure of plausibility for the inverse solution. The “consistent” inverse solution reproduces 56% of the average squared variation in the data. The local‐wind‐driven flow alone accounts for half of the model skill. The other half is attributable to remotely forced flows from the Gulf of Maine. The unexplained 44% comes from measurement errors and model errors that are not accounted for in the analysis.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/95JC03705
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1996
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  • 5
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    Space and time variability of the surface color field in the northern Adriatic Sea
    American Geophysical Union (AGU) ; 1986
    In:  Journal of Geophysical Research: Oceans Vol. 91, No. C11 ( 1986-11-15), p. 12957-12974
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 91, No. C11 ( 1986-11-15), p. 12957-12974
    Abstract: A time series of coastal zone color scanner images for the years 1979 and 1980 was used to observe the spatial and temporal variability of bio‐optical processes and circulation patterns of the northern Adriatic Sea on monthly, seasonal, and interannual scales. The chlorophyll‐like pigment concentrations derived from satellite data exhibited a high correlation with sea truth measurements performed during seven surveys in the summer of both years. Comparison of the mean pigment fields indicates a general increase in concentration values and larger scales of coastal features from 1979 to 1980. This variability may be linked to the different patterns of nutrient influx due to coastal runoff in the 2 years. The distribution of surface features is consistent with the general cyclonic circulation pattern. The pigment heterogeneity appears to be governed by fluctuations of freshwater discharge, while the dominant wind fields do not appear to have important direct effects. The Po River presents a plume spreading predominantly in a southeastern direction, with scales positively correlated with its outflow. The spatial scales of the western coastal layer, in contrast, are negatively correlated with this outflow and the plume scales. Both results are consistent with, and may be rationalized by, recent theoretical and experimental results involving a dynamical balance between nonlinear advection and bottom friction, with alternate predominance of one of the two effects.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/JC091iC11p12957
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1986
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  • 6
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    A maximum‐gradient inverse for the Gulf Stream system
    American Geophysical Union (AGU) ; 1986
    In:  Journal of Geophysical Research: Oceans Vol. 91, No. C9 ( 1986-09-15), p. 10566-10580
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 91, No. C9 ( 1986-09-15), p. 10566-10580
    Abstract: Acoustic tomography uses integrating measurements which require inverse methods to resolve the averages into estimates of spatial structure. Statistical inverse methods have been extensively used to solve the reconstruction problem over different tomographic ranges and configurations. These inverses become very difficult to apply in frontal regions like the Gulf Stream (GS) system, where the statistics are acutely inhomogeneous and anisotropic and the mean is not a likely representation of the GS front at any time. In this paper we propose an alternative inverse which asks for the solution which gives a front instead of asking for the smoothest solution. The inverse solution minimizes the errors in the fit to the data while simultaneously maximizing the sum of the squares of the gradients observed in the reconstructed section and minimizing the absolute value norm for stability. The inverse is aimed at detecting changes in the GS front, thus the data are used to estimate the perturbations to a previous estimate of the frontal structure, instead of reconstructing the entire front as a perturbation from some average state. This approach is intended to merge well with eventual dynamic updating schemes and can be used with various types of data, given a proper model. Several examples have been run intercomparing the traditional linear least squares (LLSI) with the maximum gradient inverse (MGI), from very idealized cases to a real Gulf Stream section reconstructed from hydrographic data. Different transceiver configurations were also compared and mid‐depth instruments were found to be superior to bottom mounted instruments. The simplest cases show a significant improvement in the estimate of the Gulf Stream front by the MGI compared to the weighted least squares inverse (LLSI). As the cases became more complicated (and more realistic), the differences between inverse methods become less pronounced, although the strength and location of the perturbation maxima were always determined more accurately by the MGI. The decline is at least partially due to the numerical algorithm which lumps data misfits and external constraints (the maximum gradient) into a single penalty criterion which is minimized. The most immediate way to overcome this limitation is to break up the problem into a two‐step procedure, first a least squares inverse to fit the data and second an iterative, nonlinear optimization maximizing the gradient and minimizing the absolute value norm.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/JC091iC09p10566
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1986
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  • 7
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    Acoustic tomography in the Straits of Florida
    American Geophysical Union (AGU) ; 1991
    In:  Journal of Geophysical Research: Oceans Vol. 96, No. C4 ( 1991-04-15), p. 7023-7048
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 96, No. C4 ( 1991-04-15), p. 7023-7048
    Abstract: Variability of the Florida Current has been monitored via acoustic tomography. A reciprocal tomography experiment was conducted in the eastern half of the Florida Straits during mid‐October and November, 1983. A triangular array of transceivers, with leg separations of approximately 45 km, was deployed at 27°N. The presence of a surface mixed layer in the region allowed for the ducted propagation of acoustic energy in the surface layer. A deeper layer was sampled by an unresolved group of refracted, bottom‐reflected ray arrivals. Incorporating the complete set of arrivals, we are able to obtain depth‐dependent estimates of the temperature field, current velocity, and relative vorticity. The oceanography of the region has been shown to be dominated by the lateral shifting of the surface and subsurface core of the Florida Current. The influx of westward flowing water through the Northwest Providence Channel at 26°N also appears as a large‐scale signal in the eastern Florida Straits. Low‐frequency fluctuations of temperature, current velocity, and vorticity occur at periods ranging from several days to nearly 2 weeks, and are intimately related to meandering of the Florida Current system.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/91JC00007
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1991
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  • 8
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    Regime shift of the South China Sea SST in the late 1990s
    Springer Science and Business Media LLC ; 2017
    In:  Climate Dynamics Vol. 48, No. 5-6 ( 2017-3), p. 1873-1882
    Details
    In: Climate Dynamics, Springer Science and Business Media LLC, Vol. 48, No. 5-6 ( 2017-3), p. 1873-1882
    Type of Medium: Online Resource
    ISSN: 0930-7575 , 1432-0894
    URL: Article
    DOI: 10.1007/s00382-016-3178-4
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2017
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  • 9
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    Coupling of a regional atmospheric model (RegCM3) and a regional oceanic model (FVCOM) over the maritime continent
    Springer Science and Business Media LLC ; 2014
    In:  Climate Dynamics Vol. 43, No. 5-6 ( 2014-9), p. 1575-1594
    Details
    In: Climate Dynamics, Springer Science and Business Media LLC, Vol. 43, No. 5-6 ( 2014-9), p. 1575-1594
    Type of Medium: Online Resource
    ISSN: 0930-7575 , 1432-0894
    URL: Article
    DOI: 10.1007/s00382-013-1986-3
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2014
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  • 10
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    The climatological seasonal circulation of the Mediterranean Sea
    Journal of Marine Research/Yale ; 1991
    In:  Journal of Marine Research Vol. 49, No. 3 ( 1991-08-01), p. 411-434
    Details
    In: Journal of Marine Research, Journal of Marine Research/Yale, Vol. 49, No. 3 ( 1991-08-01), p. 411-434
    Type of Medium: Online Resource
    ISSN: 0022-2402 , 1543-9542
    URL: Article
    DOI: 10.1357/002224091784995783
    Language: English
    Publisher: Journal of Marine Research/Yale
    Publication Date: 1991
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    SSG: 12
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