Please use this identifier to cite or link to this item:
http://hdl.handle.net/2122/8950| DC Field | Value | Language |
|---|---|---|
| dc.contributor.authorall | Masina, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia | en |
| dc.date.accessioned | 2014-02-27T07:43:33Z | en |
| dc.date.available | 2014-02-27T07:43:33Z | en |
| dc.date.issued | 2002-05 | en |
| dc.identifier.uri | http://hdl.handle.net/2122/8950 | en |
| dc.description | The author is indebted to S. G. Philander for his assistance throughout this study which was mostly carried out at Princeton University. I thank A. B. G. Bush for reading an earlier version of the manuscript and making many helpful comments. The Editor in Chief thanks J. Vialard and another referee for their help in evaluating this paper. | en |
| dc.description.abstract | Several numerical experiments are performed in a nonlinear, multi-level periodic channel model centered on the equator with different zonally uniform background flows which resemble the South Equatorial Current (SEC). Analy- sis of the simulations focuses on identifying stability criteria for a continuously stratified fluid near the equator. A 90 m deep frontal layer is required to destabilize a zonally uni- form, 10◦ wide, westward surface jet that is symmetric about the equator and has a maximum velocity of 100 cm/s. In this case, the phase velocity of the excited unstable waves is very similar to the phase speed of the Tropical Instability Waves (TIWs) observed in the eastern Pacific Ocean. The vertical scale of the baroclinic waves corresponds to the frontal layer depth and their phase speed increases as the vertical shear of the jet is doubled. When the westward surface parabolic jet is made asymmetric about the equator, in order to simu- late more realistically the structure of the SEC in the eastern Pacific, two kinds of instability are generated. The oscilla- tions that grow north of the equator have a baroclinic nature, while those generated on and very close to the equator have a barotropic nature. This study shows that the potential for baroclinic instabil- ity in the equatorial region can be as large as at mid-latitudes, if the tendency of isotherms to have a smaller slope for a given zonal velocity, when the Coriolis parameter vanishes, is compensated for by the wind effect. | en |
| dc.language.iso | English | en |
| dc.publisher.name | Copernicus Publications | en |
| dc.relation.ispartof | Annales Geophysicae | en |
| dc.relation.ispartofseries | /20 (2002) | en |
| dc.subject | equatorial oceanography | en |
| dc.subject | numerical modeling | en |
| dc.subject | fronts and jets | en |
| dc.title | Instabilities of continuously stratified zonal equatorial jets in a periodic channel model | en |
| dc.type | article | en |
| dc.description.status | Published | en |
| dc.type.QualityControl | Peer-reviewed | en |
| dc.description.pagenumber | 729-740 | en |
| dc.identifier.URL | http://www.ann-geophys.net/20/729/2002/angeo-20-729-2002.html | en |
| dc.subject.INGV | 03. Hydrosphere::03.01. General::03.01.01. Analytical and numerical modeling | en |
| dc.identifier.doi | 10.5194/angeo-20-729-2002 | en |
| dc.relation.references | Benilov, E. S. and Sakov, P. V.: On the linear approximation of ve- locity and density profiles in the problem of baroclinic instability, J. Phys. Ocean., 29, 1374–1381, 1999. Chang, P. and Philander, S. G. H.: Rossby Wave packets in baro- clinic mean currents, Deep-Sea Res., 36, 17–37, 1989. Charney, J. G.: The dynamics of long waves in a baroclinic westerly current, J. Meteor., 4, 135–162, 1947.Cox, M. D.: Generation and Propagation of 30-day Waves in a Nu- merical Model of the Pacific, J. Phys. Ocean., 10, 1168–1186, 1980. Donohue, K.A. and Wimbush. M.: Model results of flow instabili- ties in the tropical Pacific Ocean, J. Geophys. Res., 103, 21 401– 21 412, 1998. Eady, E. T.: Long waves and cyclone waves, Tellus, 1, 33–52, 1949. Gill, A.: Atmospheric-Ocean Dynamics, International Geophysical Series No. 30. London: Academic Press, 662, 1982. Halpern, D., Knox, R. A., and Luther, D. S.: Observations of 20-day period meridional current oscillations in the upper ocean along the Pacific equator, J. Phys. Ocean., 18, 1514–1534, 1988. Kennan, S. C. and Flament, P. J.: Observations of a Tropical Insta- bility Vortex, J. Phys. Ocean., 30, 2277–2301, 2000. Kuo, H. L.: Dynamic instability of two-dimensional non-divergent flow in a barotropic atmosphere, J. Meteorol, 6, 105–122, 1949. Legeckis, R.: Long waves in the eastern equatorial Pacific Ocean: A view from a geostationary satellite, Science, 197, 1179–1181, 1977. Lipps, F. B.: Stability of jets in a divergent barotropic fluid, J. At- mos. Sci., 20, 120–129, 1963. Luther, D. S., Knox, R. A., and Halpern, D.: Eddy heat fluxes in the upper equatorial Pacific Ocean along 140◦ W, EOS, 68, 1321, 1987. Luther, D. S. and Johnson, E. S.: Eddy energetics in the upper equa- torial Pacific during the Hawaii-to-Tahiti Shuttle Experiment, J. Phys. Ocean., 20, 913–944, 1990. Masina, S. and Philander, S. G.: An analysis of Tropical Instability Waves in a numerical model of the Pacific Ocean. Part I: Spatial variability of the waves, J. Geophys. Res., 104, C12, 29 613– 29 636, 1999. Masina, S., Philander, S. G., and Bush, A. B. G.: An analysis of Tropical Instability Waves in a numerical model of the Pacific Ocean. Part II: Generation and energetics of the waves, J. Geo- phys. Res., 104, C12, 29 637–29 661, 1999. McCreary Jr, J. P. and Yu, Z.: Equatorial dynamics in a 2 1 2 -layer model, Prog. Oceanogr., 29, 61–132, 1992. McPhaden, M. J.: Monthly period oscillations in the Pacific North Equatorial Countercurrent, J. Geophys. Res., 101, 6337–6359, 1996. McPhaden, M. J. and Ripa, P.: Wave-mean flow interactions in the equatorial ocean, Annu. Rev. Fluid Mech., 22, 167–205, 1990. Nakamura, N.: Scale selection of baroclinic instability-Effects of stratification and nongeostrophy, J. Atmos. Sci., 45, 3253–3267, 1988. Nakamura, N.: An illustrative model of instabilities in meridionally and vertically sheared flows, J. Atmos. Sci., 50, 357–375, 1993a. Nakamura, N.: Momentum flux, flow symmetry, and the nonlinear barotropic governor, J. Atmos. Sci., 50, 2159–2179, 1993b. Orlanski, I.: Localized baroclinicity: A source for meso-α cyclones, J. Atmos. Sci., 43, 2857–2885, 1986. Orlanski, I.: and Cox, M. D.: Baroclinic instability in ocean cur- rents, Geophys. Fluid Dynam., 4, 297–332, 1973. Pacanowski, R. C. and Philander, S. G. H.: Parameterization of ver- tical mixing in numerical models of Tropical Oceans. J. Phys. Ocean., 11, 1443–1451, 1981. Pacanowski, R., Dixon, K., and Rosati, A., The G.F.D.L. Modular Ocean Model Users Guide, GFDL Ocean Group Technical Re- port # 2, 1993. Perigaud, C.: Sea level oscillations observed with Geosat along the two shear fronts of the Pacific North Equatorial Countercurrent, J. Geophys. Res., 95, 7239–7248, 1990. Philander, S. G. H.: Instabilities of Zonal Equatorial Currents, J. Geophys. Res., 81, 3725–3735, 1976. Philander, S. G. H.: Instabilities of Zonal Equatorial Currents, 2, J. Geophys. Res., 83, 3679–3682, 1978. Proehl, J. A.: The role of meridional flow asymmetry in the dynam- ics of tropical instability, J. Geophys. Res., 103, 24 597–24 618, 1998. Qiao, L. and Weisberg, R. H.: Tropical instability wave kinematics: Observations from the Tropical Instability Wave Experiment, J. Geophys. Res, 100, 8677–8693, 1995. Ripa, P.: General stability conditions for zonal flows ina one-layer model on the β -plane or the sphere, J. Fluid Mech., 126, 463– 489, 1983. Ripa, P.: General stability conditions for a multi-layer model, J. Fluid Mech., 222, 119–137, 1991. Seigel, A. D.: A comment on long waves in the Pacific Ocean, J. Phys. Ocean., 15, 1881–1883, 1985. Semtner Jr., A. J. and Holland, W. R.: Numerical simulation of equatorial ocean circulation. Part I: A basic case in turbulent equilibrium, J. Phys. Ocean., 10, 667–693, 1980. Stone, P. H.: On non-geostrophic baroclinic stability, J. Atmos. Sci., 23, 390–400, 1966. Stone, P. H.: On non-geostrophic baroclinic stability: Part II, J. Atmos. Sci., 27, 721–726, 1970. | en |
| dc.description.obiettivoSpecifico | 4A. Clima e Oceani | en |
| dc.description.journalType | JCR Journal | en |
| dc.description.fulltext | open | en |
| dc.relation.issn | 0992-7689 | en |
| dc.relation.eissn | 1432-0576 | en |
| dc.contributor.author | Masina, S. | en |
| dc.contributor.department | Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia | en |
| item.openairetype | article | - |
| item.cerifentitytype | Publications | - |
| item.languageiso639-1 | en | - |
| item.grantfulltext | open | - |
| item.openairecristype | http://purl.org/coar/resource_type/c_18cf | - |
| item.fulltext | With Fulltext | - |
| crisitem.author.dept | Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione Bologna, Bologna, Italia | - |
| crisitem.author.orcid | 0000-0001-6273-7065 | - |
| crisitem.author.parentorg | Istituto Nazionale di Geofisica e Vulcanologia | - |
| crisitem.classification.parent | 03. Hydrosphere | - |
| crisitem.department.parentorg | Istituto Nazionale di Geofisica e Vulcanologia | - |
| Appears in Collections: | Article published / in press | |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| Masina_2002.pdf | main article | 2.29 MB | Adobe PDF | View/Open |
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