28 research outputs found
Excitation of Giant Monopole Resonance in Pb and Sn Using Inelastic Deuteron Scattering
The excitation of the isoscalar giant monopole resonance (ISGMR) in
Sn and Pb has been investigated using small-angle (including
) inelastic scattering of 100 MeV/u deuteron and
multipole-decomposition analysis (MDA). The extracted strength distributions
agree well with those from inelastic scattering of 100 MeV/u
particles. These measurements establish deuteron inelastic scattering at E 100 MeV/u as a suitable probe for extraction of the ISGMR strength with
MDA, making feasible the investigation of this resonance in radioactive
isotopes in inverse kinematics.Comment: 5 pages, 4 figures. To be published in Phys. Lett.
A model of multiple zonal jets in the oceans : dynamical and kinematical analysis
Author Posting. © American Meteorological Society, 2009. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 39 (2009): 2711-2734, doi:10.1175/2009JPO4093.1.Multiple alternating zonal jets observed in the ocean are studied with an idealized quasigeostrophic zonal-channel model, with the supercritical, zonal background flow imposed. Both eastward and westward background flows with vertical shear are considered. The underlying nonlinear dynamics is illuminated with analysis of the vertical-mode interactions and time-mean eddy fluxes.
Interactions between the vertical modes are systematically studied. The barotropic component of the jets is maintained by both barotropicâbarotropic and baroclinicâbaroclinic time-mean interactions; thus, the barotropic component of the jets cannot be accurately simulated with a randomly forced barotropic model. The roles of the vertical-mode interactions in driving the baroclinic component of the jets are also characterized. Not only the first but also the second baroclinic mode is found to be important for maintaining the baroclinic component of the jets, whereas the barotropic component of the jets is maintained mostly by the barotropic and first baroclinic modes.
The properties of the eddy forcing were systematically studied. It is shown that the baroclinic component of the jets is maintained by Reynolds stress forcing and resisted by form stress forcing only in the eastward background flow. In the westward background flow, the jets are maintained by form stress forcing and resisted by Reynolds stress forcing.
The meridional scaling and kinematical properties of the jets are studied as well as the roles of meridional boundaries. The Rhines scaling for meridional spacing of the jets is not generally confirmed, and it is also shown that there are multiple stable equilibria with different numbers of the time-mean jets. It is also found that the jets are associated with alternating weak barriers to the meridional material transport, but the locations of these barriers are not unique and depend on the direction of the background flow and depth. Finally, if the channel is closed with meridional walls, then the jets become more latent but the eddy forcing properties do not change qualitatively.Funding for PB was provided by
NSF Grants OCE 0344094 and OCE 0725796 and by the
research grant from the Newton Trust of the University
of Cambridge. Funding for IK was provided by NSF
Grants OCE 0346178 and 0749722. Funding for JP was
provided by NSF Grant OCE 0451086
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Accuracy assessment of recent ocean tide models
Over 20 global ocean tide models have been developed since 1994, primarily as a
consequence of analysis of the precise altimetric measurements from TOPEX/POSEIDON and as a result of parallel developments numerical tidal modeling and data assimilation. This paper
provides an accuracy assessment of 10 such tide models and discusses their benefits in many fields including geodesy, oceanography, and geophysics. A variety of tests indicate that all these tide models agree within 2-3 cm in the deep ocean, and they represent significant improvement over the classical Schwidersk1i 1980 model by approximately 5 cm rms. As a result, two tide models
were selected for the reprocessing of TOPEX/POSEIDON Geophysical Data Records in late
1995. Current ocean tide models allow an improved observation of deep ocean surface dynamic
topography using satellite altimetry. Other significant contributions include their applications in
an improved orbit computation for TOPEX/POSEIDON and other geodetic satellites, to yield
accurate predictions of Earth rotation excitations and improved estimates of ocean loading
corrections for geodetic observatories, and to allow better separation of astronomical tides from
phenomena with meteorological and geophysical origins. The largest differences between these
tide models occur in shallow waters, indicating that the current models are still problematic in
these areas. Future improvement of global tide models is anticipated with additional high-quality
altimeter data and with advances in numerical techniques to assimilate data into high-resolution
hydrodynamic models.Copyrighted by American Geophysical Union
Eddy activities of the surface layer in the western North Pacific detected by satellite altimeter and radiometer
Subtidal flow division at a shallow tidal junction
Tides influence distribution of river discharge at tidally affected channel junctions. At
the apex of a channel network in an Indonesian delta, observations of flow division suggest
that tidally averaged flow division depends on the tidal range. To understand the
mechanisms governing the subtidal flow division, an idealized hydrodynamic junction
model inspired by the observations has been set up. The barotropic model consists of two
exponentially converging tidal channels that connect to a tidal river at the junction and
solves the nonlinear shallow water equations. By varying the depth, length, eâfolding
length scale of the channel width, and hydraulic roughness in one of the two tidal
channels, the sensitivity of the subtidal flow division to those four parameters was
investigated. For depth, length, and eâfolding length scale differences between
channels the effect of tides is generally to enhance unequal subtidal flow division that
occurs in the case of river flow only. In contrast, for hydraulic roughness differences, the
tidal effect partly cancels the inequality in river flow division. The tidal effect may even
reverse the horizontal flow circulation that would occur in the absence of tides