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  • 1
    Electronic Resource
    Electronic Resource
    Fluctuation-response relations in systems with chaotic behavior (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 2247-2254 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The statistics of systems with good chaotic properties obey a formal fluctuation-response relation which gives the average linear response of a dynamical system to an external perturbation in terms of two-time correlation functions. Unfortunately, except for particularly simple cases, the appropriate form of correlation function is unknown because an analytic expression for the invariant density is lacking. The simplest situation is that in which the probability distribution is Gaussian. In that case, the fluctuation-response relation is a linear relation between the response matrix and the two-time two-point correlation matrix. Some numerical computations have been carried out in low-dimensional models of hydrodynamic systems. The results show that fluctuation-response relation for Gaussian distributions is not a useful approximation. Nevertheless, these calculations show that, even for non-Gaussian statistics, the response function and the two-time correlations can have similar qualitative features, which may be attributed to the existence of the more general fluctuation-response relation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857905
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  • 2
    Electronic Resource
    Electronic Resource
    An explanation for anomalous vortex merger in rotating-tank experiments (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 1411-1415 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Theory and simulations based on the two-dimensional Euler equation predict a critical distance of separation for the merger of two like-signed vortices. By the symmetry of the equation, this separation must be the same for both cyclone and anticyclone pairs. In rotating-tank experiments, the observed critical separation distance for anticyclone merger is in accord with predictions; however, pairs of cyclones have been found to merge in all cases examined, even with separations substantially greater than the predicted critical separation. The hypothesis that this discrepancy is due to the presence of Ekman volume fluxes, which are not incorporated in the two-dimensional theory, is examined and found not quantitatively supportable. A second hypothesis is that the parabolic curvature of the free upper surface of the fluid in the rotating tank induces motion of the cyclones toward the center of the tank and hence promotes the cyclone pair merger. Quasigeostrophic simulations which capture this "topography effect'' show good agreement with the rotating-tank experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858019
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  • 3
    Electronic Resource
    Electronic Resource
    Numerical experiments on modon stability to topographic perturbations (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 2562-2566 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A summary of a numerical study of the stability of modons to topographic perturbation is presented. Previous studies have suggested a monotonic relationship between the horizontal scale of the perturbation and the amplitude needed to destroy a modon—as the scale of the perturbation increases the strength needed for destruction decreases. The results presented here show that this relationship does not hold for scales larger than the modon radius. For large-scale perturbations, the strength needed for destruction again increases. The modon is most stable to perturbations of horizontal scale either much larger or much smaller than the modon radius. Stability graphs are presented for three types of perturbations; ridges, hills, and irregular terrain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866533
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  • 4
    Electronic Resource
    Electronic Resource
    The role of initial conditions in flow stability with an application to modons (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 2567-2572 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Lyapunov stability arguments may be used to show that an otherwise unstable flow can be stabilized by restriction of the class of possible perturbations. It is shown that, in general, such a restriction applied only to the initial perturbation does not imply stability for dynamics on the entire phase space nor does it necessarily imply a delay of the onset of instability. As a result, proofs of linear stability based on a restriction of the initial perturbation actually are not valid. In particular, certain criteria for the stability of modons given by Pierini [Dyn. Atmos. Oceans 9, 273 (1985)] and Swaters [Phys. Fluids 29, 1419 (1986)] and synthesized by Flierl [Annu. Rev. Fluid Mech. 19, 493 (1987)] do not, in fact, ensure stability. A model is used to demonstrate that these stability criteria do not preclude instantaneous onset of linear instability. The model also demonstrates that, although conservation of energy and enstrophy implies that the transfer of energy in an instability must be to scales both larger and smaller than the modon scale, the principal direction of transfer remains undetermined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866534
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  • 5
    Electronic Resource
    Electronic Resource
    A note on the dynamic boundary conditions in Munk-like circulation models (2003)
    Springer
    The European physical journal 31 (2003), S. 571-575 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 92.10.Fj Dynamics of the upper ocean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The present note deals with Munk's ocean model and proposes an alternative approach to find its solution, with special regard to the western boundary layer. We introduce a suitable “distance” between the related Sverdrup streamfunction and all the admissible streamfunctions which are valid in the western boundary layer. We prove that such distance has a minimum that singles out a unique solution. Unlike the traditional method, this procedure works without assuming a priori any dynamic boundary condition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2003-00067-9
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  • 6
    Electronic Resource
    Electronic Resource
    A non-linear model: The elliptic vortex in the Ligurian Sea (1978)
    Springer
    Meteorology and atmospheric physics 27 (1978), S. 95-101 
    Details
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung In einem nichtlinearen Schema wird die Form eines deformierten Wirbels mit Berücksichtigung der Corioliskraft analysiert. Dieser Formalismus wird zur Erklärung eines im nördlichen Ligurischen Meer gelegenen Wirbels angewendet. Einige Differenzen zwischen den experimentellen und theoretischen Ergebnissen werden besprochen.
    Notes: Summary The shape of a deformed vortex in the presence of the Coriolis force is analyzed in a non-linear scheme. This formalism is used to explain a vortex that is located in the North Ligurian Sea. Some differences between experimental and theoretical results are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02246465
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  • 7
    Electronic Resource
    Electronic Resource
    The radially symmetrical model in defining the diffusion coefficient: An application to the bay of La Maddalena Island (1982)
    Springer
    Meteorology and atmospheric physics 31 (1982), S. 137-146 
    Details
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Das allgemeine Verfahren der Anwendung der radialsymmetrischen Methode zur Bestimmung des turbulenten Diffusionskoeffizienten wird dargelegt. Daran schließt sich eine Besprechung der Methode und ihrer praktischen Anwendung.
    Notes: Summary The general procedure of application of the radially symmetrical method for the evaluation of the turbulent diffusion coefficient is presented. This allows a discussion on the method and its practical application.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02257748
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  • 8
    Electronic Resource
    Electronic Resource
    Atmospheric pressure and internal waves interaction: a resonant case (1979)
    Springer
    Meteorology and atmospheric physics 28 (1979), S. 279-291 
    Details
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Im Rahmen einer ozeanographischen Untersuchung der Zirkulation im Ligurischen Meer wird ein Fall von Resonanz zwischen Luftdruck- und internen Wellenschwankungen beschrieben. Nach einer kurzen Darstellung der durchgeführten Messungen werden im Detail die Techniken der Spektralanalyse dargelegt und auf die gesammelten Beobachtungsdaten angewendet. Die erhaltenen Ergebnisse können als Resonanzübertragung zwischen Luftdruckschwankungen und einer internen Seiche des Beckens erklärt werden.
    Notes: Summary In the frame of an oceanographic research aimed at describing marine circulation in the Ligurian Sea, a case of resonance between pressure and internal waves fluctuations is described. More in detail, after a short presentation of measurements carried out, the spectral analysis techniques are presented and applied to the data collected. The results obtained can be interpreted as a resonant transfer between the pressure fluctuations and an internal seiche of the basin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02310173
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  • 9
    Electronic Resource
    Electronic Resource
    Dispersion of passive tracers in model flows: effects of the parametrization of small-scale processes (1996)
    Springer
    Annales geophysicae 14 (1996), S. 476-484 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A set of numerical experiments is presented, in which we study the dynamics of passive particles advected by given two-dimensional velocity fields and perturbed by a non-white noise with a characteristic time 〈tau〉. Data and model results have shown that this kind of random perturbation is able to represent subgridscale processes for upper ocean mesoscale turbulence for regions of the world ocean where turbulence can be assumed to be homogeneous. Extensive computations in different fields characterized by cell-like structure, both stationary and time-dependent, representing very idealized geophysical flow situations, show that the presence of a finite correlation time scale does lead to enhanced or arrested dispersion, depending on the considered flow; however, it does not seem to affect the gross qualitative behaviour of the dispersion processes, which is primarily affected by the large-scale velocity field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-996-0476-x
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  • 10
    Electronic Resource
    Electronic Resource
    A study on the precipitation in Rome from 1782 to 1978 (1986)
    Springer
    Theoretical and applied climatology 37 (1986), S. 90-96 
    Details
    ISSN: 1434-4483
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Description / Table of Contents: Zusammenfassung Die Analyse historischer Zeitrechnung ist ein gutes Werkzeug zum Studium des vergangenen Klimas. In Rom existiert eine lange Reihe meteorologischer Beobachtungen, die bis 1782 zurückreicht. Während in einer früheren Untersuchung die Lufttemperatur betrachtet wurde, werden hier mit verschiedenen statistischen Methoden die gleichzeitig auftretenden Muster des Niederschlags untersucht. Sie zeigen einige Charakteristika im Niederschlagsregime mit Perioden, die von jahreszeitlichen bis zu jahrhundertelangen reichen.
    Notes: Summary The analysis of the historical data series is a powerful tool for the study of the past climate. There exists in Rome a long series of meteorological observations, which date back to 1782. While in a previous work the air temperature was examined, in the present one different statistical techniques are used in order to investigate the synchronous patterns of precipitations. These methods show some characteristics of the precipitation regime on a time scale running from a seasonal to a secular cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00866108
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