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Transmission and reflection of the Rossby waves in a stratified ocean with bottom topography
1082
A. Physical Oceanography
A l l 0 . Water masses and fronts 90:6894 Dewey, R.K. and J.N. Mourn, 1990. Enhancement of fronts by vertical mixing. V. geophys. Res., 95(C6):9433-9445. Observations of cool filaments off northern California indicate that within the cool (dense) core of filaments the raised pycnocline inhibits the penetration of surface-generated mixing. A greater portion of energy input at the surface is available for entrainment of dense fluid through the pycnocline and into the surface mixed layer where the pycnocline is shallow. Hence surface-forced mixing may cause a more rapid increase in mixed layer density within the cool filament than outside the filament, resulting in an enhanced horizontal density gradient in the mixed layer which could result in an accelerated mixed layer in the direction of the preexisting geostrophic flow. Horizontal variability of pycnocline erosion may not be properly taken into account in some models and should more realistically be parameterized by including dependence on pycnocline depth. Coll. of Oceanogr., Oregon State Univ., Oceanogr. Admin. Bldg. 104, Corvallis, OR 97331, USA. 90:6895 Kuo, A.Y. et al., 1990. Practical application of theory for tidal-intrusion fronts. J. Wat Way Port coast. Ocean Engng, Am. Soc. civ. Engrs, 116(3):341361. A simple theoretical model was applied to interpret the characteristics of an estuarine front that forms at the early stage of each flood tide off Newport News Point, in the lower James River, Virginia. The observed depths of diving of denser water at the front, and the upriver movement of the front are explained theoretically. A man-made island to facilitate port expansion was proposed for downriver of the front. A numerical model is used to predict the impact of the proposed island on frontal characteristics, particularly with respect to the entrainment and transport of oyster larvae to the lower portion of the water column, where net transport is upriver toward seed-oyster beds. Results indicate that the transport capacity of the front would be markedly reduced by island construction at the proposed sites. Virginia Inst. of Mar. Sci., Gloucester Point, VA 23062, USA.
A150. Tides and sea level 90:6896 Cheney, R.E. et al., 1989. Monitoring tropical sea
OLR (1990) 37 (12)
level in near-real time with Geosat altimetry. Johns Hopkins APL tech. Dig, 10(4):362-368. Geosat is the first altimeter satellite used for long-term, continuous monitoring of sea level. Since its launch in 1985, we have been using the data to study connections between the ocean and atmosphere in the tropical Pacific. In early 1987, shortly after the onset of the 1986-87 E1 Nifio, we began processing these data in near-real time to monitor sea level during this climatic event. An operational N O A A program of monthly sea-level monitoring has evolved that encompasses all three tropical oceans. Natl. Geodetic Survey, NOAA, Washington, DC, USA. 90:6897 Ooe, Masatsugu, 1989. Effects of configuration and bathymetry of the oceans on the tidal dissipation of the Earth's rotation. J. Phys. Earth, 37(5):345355. Discrete tidal equations with linear dissipation terms are solved for the M 2 ocean tide using present oceans and a Permian ocean. Model properties are also examined by changing parameters related to bottom friction and eddy viscosity. Results show that the M2 tide explains, for the most part, the tidal dissipation of the Earth's rotation; it appears that tidal dissipation was slightly smaller in the Permian era than at present. Natl. Astron. Observ., Div. of Earth Rotation, Mizusawa, Iwate, Japan.
A160. Waves, oscillations 90:6898 Aoki, Shigeaki, 1989. Transmission and reflection of the Rosshy waves in a stratified ocean with bottom topography. J. oceanogr. Soc. Japan, 45(5):321-338. In the parameter range where only the barotropic Rossby waves can propagate in the region outside the slope, the bottom-trapped wave plays the same role as the topographic Rossby wave in a homogeneous ocean, hence transmission is weak unless phase matching takes place. When both barotropic and baroclinic Rossby waves can propagate outside the slope, the total transmission can be strong. The bottom-trapped wave affects transmission and reflection, suggesting that the Rossby wave is transmitted as a mode different from the incident mode. When the number of the wavy modes on the slope is smaller than that of the Rossby wave modes outside the slope, strong reflection occurs. Weakening of the stratification near the bottom is almost equivalent to reducing the effect of the slope. Ocean Res. Inst.,
OLR (1990).t.7 (12)
A. Physical Oceanography
Univ. of Tokyo, 1-15-1, Minamidai, Nakano-ku, Tokyo I64, Japan. 90:6899
Baddour, R.E. and S. Song, 1990. On the interaction between waves and currents. Ocean Engng, 17(I/2):1-21. The interaction of a current-free plane surface wave train of fixed frequency and a uniform wave-free current normal to the wave crests in the same or opposite direction to wave propagation is described. The parameters describing the wave-current field generated by the interaction, namely the wave height, wave length, stream current and water depth, are calculated numerically by solving a set of nonlinear equations. Possible solutions are identified a posteriori. Contrary to other approaches the additional contribution to the change in the mean value of the current and mean water depth is not neglected in this work. Fac. of Engng and Appl. Sci., Memorial Univ., St. John's, N F A I B 3X5, Canada. 90:6900
Freilich, M.H., R.T. Guza and S.L. Elgar, 1990. Observations of nonlinear effects in directional spectra of shoaling gravity waves. J. geophys. Res, 95(C6):9645-9656. The spatial evolution of a directionally spread wave field on a near-planar natural beach is examined using data from longshore arrays of pressure sensors and wave staffs at 10.3 m and 4.1 m depth. tligh-resolution frequency-directional spectra from the deeper array are used to initialize a linear refraction model; resulting predictions are compared with frequency-direction measurements at the shallow array. Linear theory inaccurately predicts both the shapes of directional spectra in shallow water and the total variances in some frequency bands. The discrepancies are largest for frequencies associated with maxima in the bicoherenee spectrum, suggesting the importance of nonlinear effects. Prominent features in the measured directional spectra at the shallow array are consistent with energy transfers resulting from near-resonant triad interactions in the shoaling wave-field. Jet Propulsion Lab., California Inst. of Tech., Pasadena, CA 91109, USA. 90:6901
Golin'ko, V.I. and V.I. Malyzhenkova, 1988. Reflection from a vertical wall of a tsunami propagating in a channel of variable cross section, lzv.
Atmos. Ocean Phys. (a translation of Fiz. Atmos. Okeana), 2401):871-875. Gor'kiy Polytechnic Inst., USSR.
1083
90:6902
Mitsuyasu, Ilisashi and Tsuyoshi Uji, 1989. A comparison of observed and calculated directional wave spectra in the East China Sea. J. oceanogr. Soc. Japan, 45(5):338-349. It is shown that the numerical wave model MRI can predict rather well not only the frequency spectrum, but also the angular distribution function of the spectrum. The frequency dependence of the calculated angular distribution function is quite similar to that observed; the angular distribution is narrower for the spectral components near the peak spectral frequency but widens toward high frequencies and approaches the cos20-distribution. Res. Inst. for Appl. Mech., Kyushu Univ., Kasuga 816, Japan. 90:6903 Panchang, V.G. et al., 1990. Numerical simulation of irregular wave propagation over shoal. J. WatWay Port coast. Ocean Engng, Am. Soc. civ. Engrs, 116(3):324-340. As an approximation, the propagation characteristics of a regular wave train (with properties equal to that of the significant wave) are determined, instead of those of the actual irregular sea state. However, recent investigations have shown that for the case of combined refraction/diffraction of waves by a shoal, the propagation characteristics of the irregular and equivalent regular (monochromatic) wave conditions can be vastly different. Although the monochromatic representation gives a poor approximation of the spectral conditions, this study shows that a monochromatic refraction/diffraction model can be used to make spectral calculations that agree closely with actual irregular conditions observed in a hydraulic model. Further, these calculations can also help explain all the observed differences in the propagation of regular and various types of spectral conditions over the shoal. Cir. Engng Dept., Univ. of Maine, Orono, ME 04469, USA. 90:6904
Souganidis, P.E. and W.A. Strauss, 1990. Instability of a class of dispersive solitary waves. Proc. R. Soe. Edinb, 114A(3-4): 195-212. Dept. of Math., Brown Univ., Providence, RI 02912, USA. 90:6905 Swan, C. and J.F.A. Sleath, 1990. A second approximation to the time-mean Lagrangian drift beneath a series of progressive gravity waves. Ocean Engng, 17(I/2):65-79. A fourth-order solution is derived for the mean drift induced by a steady train of waves in water of constant depth. New measurements are made of the
A. Physical Oceanography
A l l 0 . Water masses and fronts 90:6894 Dewey, R.K. and J.N. Mourn, 1990. Enhancement of fronts by vertical mixing. V. geophys. Res., 95(C6):9433-9445. Observations of cool filaments off northern California indicate that within the cool (dense) core of filaments the raised pycnocline inhibits the penetration of surface-generated mixing. A greater portion of energy input at the surface is available for entrainment of dense fluid through the pycnocline and into the surface mixed layer where the pycnocline is shallow. Hence surface-forced mixing may cause a more rapid increase in mixed layer density within the cool filament than outside the filament, resulting in an enhanced horizontal density gradient in the mixed layer which could result in an accelerated mixed layer in the direction of the preexisting geostrophic flow. Horizontal variability of pycnocline erosion may not be properly taken into account in some models and should more realistically be parameterized by including dependence on pycnocline depth. Coll. of Oceanogr., Oregon State Univ., Oceanogr. Admin. Bldg. 104, Corvallis, OR 97331, USA. 90:6895 Kuo, A.Y. et al., 1990. Practical application of theory for tidal-intrusion fronts. J. Wat Way Port coast. Ocean Engng, Am. Soc. civ. Engrs, 116(3):341361. A simple theoretical model was applied to interpret the characteristics of an estuarine front that forms at the early stage of each flood tide off Newport News Point, in the lower James River, Virginia. The observed depths of diving of denser water at the front, and the upriver movement of the front are explained theoretically. A man-made island to facilitate port expansion was proposed for downriver of the front. A numerical model is used to predict the impact of the proposed island on frontal characteristics, particularly with respect to the entrainment and transport of oyster larvae to the lower portion of the water column, where net transport is upriver toward seed-oyster beds. Results indicate that the transport capacity of the front would be markedly reduced by island construction at the proposed sites. Virginia Inst. of Mar. Sci., Gloucester Point, VA 23062, USA.
A150. Tides and sea level 90:6896 Cheney, R.E. et al., 1989. Monitoring tropical sea
OLR (1990) 37 (12)
level in near-real time with Geosat altimetry. Johns Hopkins APL tech. Dig, 10(4):362-368. Geosat is the first altimeter satellite used for long-term, continuous monitoring of sea level. Since its launch in 1985, we have been using the data to study connections between the ocean and atmosphere in the tropical Pacific. In early 1987, shortly after the onset of the 1986-87 E1 Nifio, we began processing these data in near-real time to monitor sea level during this climatic event. An operational N O A A program of monthly sea-level monitoring has evolved that encompasses all three tropical oceans. Natl. Geodetic Survey, NOAA, Washington, DC, USA. 90:6897 Ooe, Masatsugu, 1989. Effects of configuration and bathymetry of the oceans on the tidal dissipation of the Earth's rotation. J. Phys. Earth, 37(5):345355. Discrete tidal equations with linear dissipation terms are solved for the M 2 ocean tide using present oceans and a Permian ocean. Model properties are also examined by changing parameters related to bottom friction and eddy viscosity. Results show that the M2 tide explains, for the most part, the tidal dissipation of the Earth's rotation; it appears that tidal dissipation was slightly smaller in the Permian era than at present. Natl. Astron. Observ., Div. of Earth Rotation, Mizusawa, Iwate, Japan.
A160. Waves, oscillations 90:6898 Aoki, Shigeaki, 1989. Transmission and reflection of the Rosshy waves in a stratified ocean with bottom topography. J. oceanogr. Soc. Japan, 45(5):321-338. In the parameter range where only the barotropic Rossby waves can propagate in the region outside the slope, the bottom-trapped wave plays the same role as the topographic Rossby wave in a homogeneous ocean, hence transmission is weak unless phase matching takes place. When both barotropic and baroclinic Rossby waves can propagate outside the slope, the total transmission can be strong. The bottom-trapped wave affects transmission and reflection, suggesting that the Rossby wave is transmitted as a mode different from the incident mode. When the number of the wavy modes on the slope is smaller than that of the Rossby wave modes outside the slope, strong reflection occurs. Weakening of the stratification near the bottom is almost equivalent to reducing the effect of the slope. Ocean Res. Inst.,
OLR (1990).t.7 (12)
A. Physical Oceanography
Univ. of Tokyo, 1-15-1, Minamidai, Nakano-ku, Tokyo I64, Japan. 90:6899
Baddour, R.E. and S. Song, 1990. On the interaction between waves and currents. Ocean Engng, 17(I/2):1-21. The interaction of a current-free plane surface wave train of fixed frequency and a uniform wave-free current normal to the wave crests in the same or opposite direction to wave propagation is described. The parameters describing the wave-current field generated by the interaction, namely the wave height, wave length, stream current and water depth, are calculated numerically by solving a set of nonlinear equations. Possible solutions are identified a posteriori. Contrary to other approaches the additional contribution to the change in the mean value of the current and mean water depth is not neglected in this work. Fac. of Engng and Appl. Sci., Memorial Univ., St. John's, N F A I B 3X5, Canada. 90:6900
Freilich, M.H., R.T. Guza and S.L. Elgar, 1990. Observations of nonlinear effects in directional spectra of shoaling gravity waves. J. geophys. Res, 95(C6):9645-9656. The spatial evolution of a directionally spread wave field on a near-planar natural beach is examined using data from longshore arrays of pressure sensors and wave staffs at 10.3 m and 4.1 m depth. tligh-resolution frequency-directional spectra from the deeper array are used to initialize a linear refraction model; resulting predictions are compared with frequency-direction measurements at the shallow array. Linear theory inaccurately predicts both the shapes of directional spectra in shallow water and the total variances in some frequency bands. The discrepancies are largest for frequencies associated with maxima in the bicoherenee spectrum, suggesting the importance of nonlinear effects. Prominent features in the measured directional spectra at the shallow array are consistent with energy transfers resulting from near-resonant triad interactions in the shoaling wave-field. Jet Propulsion Lab., California Inst. of Tech., Pasadena, CA 91109, USA. 90:6901
Golin'ko, V.I. and V.I. Malyzhenkova, 1988. Reflection from a vertical wall of a tsunami propagating in a channel of variable cross section, lzv.
Atmos. Ocean Phys. (a translation of Fiz. Atmos. Okeana), 2401):871-875. Gor'kiy Polytechnic Inst., USSR.
1083
90:6902
Mitsuyasu, Ilisashi and Tsuyoshi Uji, 1989. A comparison of observed and calculated directional wave spectra in the East China Sea. J. oceanogr. Soc. Japan, 45(5):338-349. It is shown that the numerical wave model MRI can predict rather well not only the frequency spectrum, but also the angular distribution function of the spectrum. The frequency dependence of the calculated angular distribution function is quite similar to that observed; the angular distribution is narrower for the spectral components near the peak spectral frequency but widens toward high frequencies and approaches the cos20-distribution. Res. Inst. for Appl. Mech., Kyushu Univ., Kasuga 816, Japan. 90:6903 Panchang, V.G. et al., 1990. Numerical simulation of irregular wave propagation over shoal. J. WatWay Port coast. Ocean Engng, Am. Soc. civ. Engrs, 116(3):324-340. As an approximation, the propagation characteristics of a regular wave train (with properties equal to that of the significant wave) are determined, instead of those of the actual irregular sea state. However, recent investigations have shown that for the case of combined refraction/diffraction of waves by a shoal, the propagation characteristics of the irregular and equivalent regular (monochromatic) wave conditions can be vastly different. Although the monochromatic representation gives a poor approximation of the spectral conditions, this study shows that a monochromatic refraction/diffraction model can be used to make spectral calculations that agree closely with actual irregular conditions observed in a hydraulic model. Further, these calculations can also help explain all the observed differences in the propagation of regular and various types of spectral conditions over the shoal. Cir. Engng Dept., Univ. of Maine, Orono, ME 04469, USA. 90:6904
Souganidis, P.E. and W.A. Strauss, 1990. Instability of a class of dispersive solitary waves. Proc. R. Soe. Edinb, 114A(3-4): 195-212. Dept. of Math., Brown Univ., Providence, RI 02912, USA. 90:6905 Swan, C. and J.F.A. Sleath, 1990. A second approximation to the time-mean Lagrangian drift beneath a series of progressive gravity waves. Ocean Engng, 17(I/2):65-79. A fourth-order solution is derived for the mean drift induced by a steady train of waves in water of constant depth. New measurements are made of the