Physical oceanography

Oceanographic Literature Review

(1987) 34 (1)

The citations are those received in the editorial office during the period 1-31 October, 1986. Most are accompanied by a short annotation or abstract and, when obtainable, by the first author's address. The citations are classified under six main headings and about 130 sub-headings (see the table of contents). Subject and author indexes are published for the first three quarters of the year with an annual cumulation. See the preface for additional explanatory material.

A. PHYSICAL OCEANOGRAPHY

AI0. Apparatus and methods

87:0001 Billard, Brian, 1986. Estimation of a mean sea surface

reference in the WRELADS airborne depth sounder. Appl. Opt., 25(13):2067-2073.

Algorithms developed to achieve an accurate mean sea surface reference for the laser-based airborne depth sounder WRELADS are presented, and their performance under extensive testing of that system is assessed. They are shown to generate successfully an accurate mean sea surface reference under a wide range of conditions that might be expected opera- tionally. Dept. of Defence, Def. Sci. and Tech. Organ., GPO Box 2151, Adelaide 5001, Australia.

87:0002 Billard, Brian, 1986. Rogue point elimination in

airborne laser hydrography. Appl. Opt., 25(13): 2074-2079. Dept. of Defence, Def. Sci. & Tech. Organ., GPO Box 2151, Adelaide 5001, Austra- lia.

87:0003 Billard, Brian, 1986. Remote sensing of scattering

coefficient for airborne laser hydrography. Appl. Opt., 25(13):2099-2108. Dept. of Defence, Def. Sci. & Tech. Organ., GPO Box 2151, Adelaide 5001, Australia.

87:0004 Billard, Brian, R.H. Abbot and M.F. Penny, 1986.

Airborne estimation of sea turbidity parameters from the WRELADS laser airborne depth sounder. Appl. Opt., 25(13):2080-2088. Dept. of De- fence, Def. Sci. and Tech. Organ., GPO Box 2151, Adelaide 5001, Australia.

87:0005 Billard, Brian, R.H. Abbot and M.F. Penny, 1986.

Modeling depth bias in an airborne laser hydrographic system. Appl. Opt., 25(13):2089-2098. Dept. of Defence, Def. Sci. & Tech. Organ., GPO Box 2151, Adelaide 5001, Australia.

2 A. Physical Oceanography OLR (1987) 34 ( I )

87:0006 Billard, Brian and P.J. Wilsen, 1986. Sea surface and

depth detection in the WRELADS airborne depth sounder. Appl. Opt., 25(13):2059-2066.

Algorithms are presented which have been developed for the WRELADS airborne depth sounder for the detection and location of sea surface and sea bottom reflections within the waveform of 256 consecutive 2-ns samples of received green light energy. A concept of pulse confidence (related to SNR) is developed and shown to be related to the probability that a pulse detected as a sea bottom reflection is valid. Dept. of Defence, GPO Box 2151, Adelaide 5001, Australia.

87:0007 Chiswell, S.M., D.R. Watts and Mark Wimbush,

1986. Using inverted echo sounders to measure dynamic height in the eastern equatorial Pacific during the 1982-1983 El Nifio. Deep-Sea Res., 33(7A):981-991.

We investigate the relationship between the dynamic height anomaly (AD) and round-trip acoustic travel time (r) measured by inverted echo sounders (IES) in the eastern equatorial Pacific. Salinity variations in the upper 50 m have little effect on ~" but do affect surface dynamic height. Consequently, in the eastern equatorial Pacific, it is better to interpret z as a record of dynamic height below 50 dbar. The slope of the calibration is -60 dyn m s ~, controlled mainly by the highly energetic E1 Nifio signal, and is ~17% steeper than the simulated IES response to the first baroclinic mode. Grad. Sch. of Oceanogr., Univ. of Rhode Island, Narragansett, RI 02882, USA.

87:0008 Minnett, P.J., 1986. A numerical study of the effects

of anomalous North Atlantic atmospheric conditions on the infrared measurement of sea surface temperature from space. J. geophys. Res., 91(C7):8509-8521.

A line-by-line radiation transfer model is used to simulate the brightness temperatures measured in the atmospheric 'window' between 10 and 13/~m by the advanced very high resolution radiometer (AVHRR/2) on the NOAA 7 satellite. It is found that the consequences of humidity anomalies are greater if they occur at height (pressure of ~850 mbar), whereas temperature anomalies have greater effect if they are in the lower troposphere. SST retrieval coefficients are derived, tested, and found to be accurate. The mean errors in SST can be a few tenths of a Kelvin in extremely anomalous atmospheric conditions, large enough to be of concern to climate researchers but probably too small to permit

direct verification by comparison with currently avai lable convent ional SST measurements. SACLANT ASW Research Centre, La Spezia, Italy.

87:0009 Penny, M.F. et al., 1986. Airborne laser hydrography

in Australia. Appl. Opt., 25(13):2046-2058.

The Australian laser airborne depth sounder WRELADS II was developed to demonstrate the feasibility of using airborne laser techniques for hydrographic survey. This paper describes the system, the experimental program used for its evaluation, and some results obtained by it. Dept. of Defence, Def. Sci. and Tech. Organ., GPO Box 2151, Adelaide 5001, Australia.

A40. Area studies, surveys

87:0010 Hisard, P., C. Henin, R. Houghton, B. Piton and P.

Rual, 1986. Oceanic conditions in the tropical Atlantic during 1983 and 1984. Nature, Lond., 322(6076):243-245.

Observed variations in the thermal field and in the zonal currents along several meridians are described. In early 1984, the upper ocean, especially on the eastern side of the ocean basin, was substantially warmer than during the corresponding period a year earlier. Most of this change in heat content was the result of a deeper thermocline. During this time an unusual eastward surface current appeared to the south of the Equator undoubtedly contributing to large zonal heat fluxes. The decrease in the surface winds between 1983 and 1984 is presumably re- sponsible for these change. ORSTOM/LPDA, Univ. P. et M. Curie, 4 Place Jussieu 75005 Paris, France.

87:0011 Katz, E.J., Philippe Hisard, J.-M, Verstraete and S.L.

Garzoli, 1986. Annual change of sea surface slope along the Equator of the Atlantic Ocean in 1983 and 1984. Nature, Lond.. 322(6076):245-247.

Here we describe the sea surface slope derived fronl three complementary methods: hydrographic stations, pressure gauges and inverted echo sounders. Together the three provide a detailed description of the temporal variation of the sea surface slope, which is then compared to a wind-stress time series. The dominant signal, in both sea slope and wind- stress, is the annual cycle, although amplitude and phase vary interannually. The annual increase in sea surface slope along the Equator in the western and central basins lags the onset of the SE trade wind.

O L R (1987) 34 { I ) A. Physical Oceanog raphy 3

l)uring the boreal winter of 1983-84 a strong rise in sea level occurred against the African coast, accompanied by a leveling of the sea surface to the west. At the same time. an ahnost comt,lete relaxation of eastward wind stress on the Equator was observed near the centre of the basin. Lamont-Dohertv Geol. Observ. Palisades, NY 10964, USA.

87:0012 Kelly J., Rolando, J.L. Blanco and Maida Diaz V.,

1985. Hydrography of the Bransfield Strait during 1984 southern summer. SIBEX-Phase I. Inst. Antart. Chil. Ser. cient., 33:15-45.

The results showed some differences with the ones obtained during FIBEX. SST and salinity were in general higher in all areas studied. The water masses and types identified coincided with the ones described for FIBEX, with differences in the surface layer, which was warmer. The geopotential topography showed a main flow to the NE in the center and northern part of the strait. The southern part showed a flow to the SW generated in the Antarctic Sound which runs up to Trinity Island, where it joins the main flow. Inst. de Fomento Pesq., Av. Pedro de Valdivia 2633, Santiago, Chile.

87:0013 Lutjeharms, J.R.E. and W.J. Emery, 1983. The

detailed thermal structure of the upper ocean layers between Cape Town and Antarctica [salinity and temperature measurements] during the period Jan.-Feb. 1978. S. Afr. J. Antarct. Res., 13:3-14. NRIO, CSIR, P.O. Box 320, Stellen- bosch 7600, South Africa.

87:0014 Miller, D.G.M. and B.B.S. Tromp, 1982. The

hydrology of waters close to Gough Island [Southern Ocean]. S. Aft. J. Antarct. Res., 12:23-33. Sea Fish. Res. Inst., Cape Town, South

Africa.

87:0015 Rochford, D.J., 1986. Interannual changes in sea

surface temperatures and salinities of the Coral and Tasman seas between 1966 and 1977. CSIRO mar. Labs Rept, 172:31pp. CSIRO, GPO Box 1538, Hobart, Tas. 7001, Australia.

87:0016 Rojas R., Ricardo, 1985. Description of the thermal

structure of the Bransfield Strait based on XBT observations. Inst. Antart. Chil. Ser. cient., 33: 83-114.

Eighty-two SIBEX-Phase I surface salinity and XBT samples showed higher temperatures at every depth compared to observations from FIBEX. Two features were observed, a meander between Deception and Brabante islands, and a cyclonic eddy south of King George Island. Dept. de Oceanogr., Inst. Hydrograf., Casilla 324, Valparaiso, Chile.

87:0017 Sarma, M.S.S. and L.V.G. Rao, 1986. Currents and

temperature structure off Godavari (east coast of India) during September 1980. Indian J. mar. Sci., 15(2):88-91.

The surface drift was ~ 2 - 3 knots and was directed NE to E. Currents recorded at different depths (15, 115 and 240 m) had speeds ~1 knot, showed variation in direction with time and exhibited a velocity shear. Temperature of the surface waters was about 30°C and that of the near bottom waters about 11.5°C. There was no well-defined mixed layer and the temperature gradually decreased with depth during most of the period. Natl. Inst. of Oceanogr., Dona Paula, Goa 403 004, India.

87:0018 Taupier-Letage, Isabelle and Claude Millot, 1986.

General hydrodynamical features in the Ligurian Sea inferred from the DYOME experiment. Oceanologica A cta, 9(2): 119-131.

Thirty current meters set in place for one year were complemented by hydrology, drifting buoys and infrared images. It appears that the intense mesoscale activity in the north is limited to winter and has a large vertical extent, while in the south it is quasi-permanent and mainly restricted to surface layers. In December-January, intense mesoscale phenomena first develop in the northern Ligurian Sea while the structure of the Ligurian Current changes markedly (isotachs become steeper). Lab. d'Oceanogr. Phys., Antenne de Toulon, BP 330, 83507 La Seyne-sur-Mer, France.

87:0019 Xi, Pangen, Shuzhen Zhang and Shizuo Feng, 1985.

An investigation on numerical modeling of circulation in the East China Sea. Acta oceanol, sin. (English version), 4(4):510-514.

Numerical modeling and observations are in agreement, and the dynamics of circulation in the East China Sea reveal control by boundary forces, water depth and thermohaline effect with the wind stress playing a minor role. Shandong Coll. of Oceanol., Qingdao, People's Republic oi China.

4 A. Physical Oceanography O L R (1987) 34 ( I

A50. General hydrography (distribution of c o m m o n oceanic properties)

87:0020 Enfield, D.B., 1986. Zonal and seasonal variations of

the near-surface heat balance of the equatorial Pacific Ocean. J. phys. Oceanogr., 16(6):1038- 1054.

This study calculates a detailed climatological inventory of the oceanic heat balance in the equatorial Pacific. The gridded climatology of Weare et al. is used as an estimate of net surface heating. Zonal and meridional/vertical advection are estimated using the gridded climatologies for wind stress (Wyrtki and Meyers) and SST (Reynolds), plus estimates of zonal transport. Meridional diffusion of heat into the cold tongue has been estimated and the terms of the heat balance have been resolved by ten-degree longitude zones and by month. The computed residual heat flux was examined for consistency with expectations about the remaining, vertical diffusion process. The effects of using the alternate climatologies of Esbensen and Kushnir and Reed for the net surface heating are also calculated. Coll. of Oceanogr., Oregon State Univ., Corvallis, OR 97331, USA.

87:0021 Gross, T.F., A.J. Williams III and W.D. Grant, 1986.

Long-term in-situ calculations of kinetic energy and Reynolds stress in a deep sea boundary layer. J. geophys. Res., 91(C7):8461-8469.

Long-term measurements of Reynolds stress and kinetic energy are necessary to characterize the bottom boundary layer during storms which transport sediment in the HEBBLE area on the Nova Scotia Rise. The data indicate a bottom boundary layer, which is usually transitional, with bottom roughness scaling between viscous and rough. Direct measurements showed that the stress was much less than that indicated by the slope of the transitional mean logarithmic velocity profile. It appears that the mean westward flow must be accompanied by a train of internal tidal waves to achieve the velocities necessary to be identified as 'benthic storms.' Skidaway Inst. of Oceanogr., Savannah, GA, USA.

87:0022 Pedlosky, Joseph, 1986. The buoyancy- and wind-

driven ventilated thermocline. J. phys. Oceanogr., 16(6): 1077-1087.

An exact solution for the ventilated region of the subtropical gyre is found under the condition that the ratio of the buoyancy flux to Ekman pumping is a function of latitude alone. It demonstrates the

general westward shift of streamlines when the subtropical gyre is heated and the enlargement of the eastern shadow zone. The flow in the shadow zone is described, in most instances, for the case of relatively small buoyancy flux. There is a broad eastward zone in which the deep flow is northeastward and a narrow zone between this branch and the ventilated fluid in which the shadow zone flow is returned in a relatively swift current nearly preserving potential vorticity. For buoyancy/Ekman flux ratios which are nearly independent of position, the eastern branch of the shadow zone circulation lacks a beta spiral and the meridional transport can be simply calculated as a direct response to the heating. For sufficiently large heating, the model predicts pinch- off of the cold water layer along a latitude circle in the ventilated zone, south of which the solution loses validity. WHOI, Woods Hole, MA 02543, USA.

87:0023 Stravisi, Franco and Fulvio Crisciani, 1986. Esti-

mation of surface heat and buoyancy fluxes in the Gulf of Trieste by means of bulk formulas. Boll. Oceanol. teor. appl., 4(1):55-62.

Total heat flux from the sea, about 20 W/m: during spring and summer, increasing to 1 l0 W / m z during autumn and winter, is balanced by an annual mean meridional flux of 65 W/m 2. The buoyancy flux is always negative (41 ~tW/m ~) owing to the strong influence of river runoff, except during January and February when small positive fluxes are observed. As a result, the northern Adriatic Sea is a heat sink and a basin of dilution. Only severe winter cooling can lead to the formation of the characteristic dense water. Ist. Sperimentale Talassografico, CNR, Tri- este, Italy.

A80. Circulation

87:0024 Mangum, L.J., S.P. Hayes and J.M. Toole, 1986.

Eastern Pacific Ocean circulation near the onset of the 1982-1983 El Nifio. J. geophys. Res., 91(C7):8428-8436.

Over a l-month period during the initial stages of the 1982-1983 E1 Niflo, hydrographic and velocity profiling measurements were made in the eastern equatorial Pacific by two research vessels. Track lines approximated a square, centered near the Galdpagos Islands with approximately meridional sections at 95°W and 85°W and nearly zonal sections at about 5°N and 5°S. Water mass characteristics and estimated currents of these sections are discussed. PMEL, NOAA, Seattle, WA, USA.

OLR (1987) 34 ( I ) A. Physical Oceanograph? 5

87:0025 Simons, T.J., 1986. The mean circulation of unstrat-

ified water bodies driven by nonlinear topographic wave interactions. J. phys. Oceanogr., 16(6): 1138-1142.

Based on climatological wind records for the Great Lakes region, the mean circulation for unstratified seasons is dominated by rectified effects of nonlinear topographic wave interactions. It is also shown that the dependence of the rectified flow on the frequency of periodic forcing is similar to the linear topographic response to wind with resonance characteristics for certain frequencies determined by topography and friction. Natl. Water Res. Inst., Burlington, ON L7R 4A6, Canada.

87:0026 Strub, P.T. and T.M. Powell, 1986. Wind-driven

surface transport in stratified closed basins: direct versus residual circulations. J. geophys. Res., 91(C7):8497-8508.

A numerical model was used to investigate wind- driven circulation in Lake Tahoe, California-Ne- vada. Two types of circulation are identified: 'direct' circulations, in which the current directions remain relatively constant and the mean circulation formed over several days resembles the instantaneous circulation, and 'residual' circulations, in which the currents fluctuate continuously and the mean circulation is characterized by small net displacements of parcels after large oscillations. Previous studies of stratified closed basins have emphasized residual circulations caused by cyclonically propagating internal basin modes, resulting in a single cyclonic mean gyre during light to moderate winds. Obser- vations at Lake Tahoe have shown currents which are more constant in direction, with a double-gyre pattern of surface circulation, dominated by an anticyclonic northern gyre. Use of the model to calculate the vorticity budget clarifies the role of the wind stress curl in creating the direct double gyre. Coll. of Oceanogr., Oregon State Univ., Corvallis, OR 97331, USA.

A90. Currents

87:0027 Clarke, A.J. and Stephen Van Gorder, 1986. A

method for estimating wind-driven frictional, time-dependent, stratified shelf and slope water flow. J. phys. Oceanogr., 16(6):1013-1028.

Friction, the alongshore pressure gradient and time-dependent effects are all of lowest-order im- portance in the dynamics of wind-driven fluctuating

currents and sea levels on continental shelves. Previous work has shown that when all these effects are included, the ocean response can be described by an infinite sum of coastal-trapped waves whose amplitudes satisfy a fully coupled infinite set of forced, first-order wave equations. We present a practical method for solving this coupled set of equations for general low-frequency, large-scale wind stress forcing as input. Convergence properties of the solution are examined analytically. Dept. of Oceanogr., Florida State Univ., Tallahassee, FL 32306, USA.

87:0028 Hameed, T.S.S., M. Baba and K.V. Thomas, 1986.

Computation of longshore currents. Indian J. mar. Sci., 15(2):92-95.

Breaker parameters, beach slopes and sediment characteristics, collected from 2 distinctive coasts, are used to compute the longshore current velocities with 4 widely used models, viz. Longuet-Higgins', Komar's and their modified versions. The longshore current velocities are overestimated by Longuet- Higgins when compared with the measured values. The equations of Komar provide comparable velocities. Komar's suggestion that the ratio of bottom slope and frictional drag coefficient is constant is reinforced. Centre for Earth Sci. Studies, Regional Centre, Cochin 682 018, India.

87:0029 Hughes, R.L., 1986. On the conjugate behaviour of

weak along-shore flows. Tel/us, 38A(3):277-284.

Using a simple analytical model containing a step shelf in a rotating ocean, confirmation is found for the idea that unstratified positively directed currents (poleward on western boundaries, equatorward on eastern boundaries) may be arranged in one of two structural forms each of which transports the same flux of each water type. These structural forms are referred to as conjugate structural forms of the current. It is shown that as the velocity is decreased in a subcritical structure of fixed width, the conjugate supercritical structure continues to exist but with decreased width as well as velocity. At rest, conditions may be obtained by letting the flow tend to zero in either the subcritical structure of fixed width or its conjugate supercritical structure, How- ever, the branch of the dispersion curve that comes to correspond to shelf waves in the at rest state depends on whether this state is approached as the weak flow limit of a subcritical or supercritical flow. Dept. of Geol. and Geophys., Yale Univ., P.O. Box 6666, New Haven, CT 06511, USA.

6 A. Ph,, sica[ Oceanographx O L R (1987) 34 ( I )

87:0030 Miao, Yutian, Shanqing Yu and Rongzhen Qiao,

1985. The variation characteristics of the Kuro- shio structure at the E section. Acta oceanol, sin. (English version), 4(1):9-20.

The E section is analyzed for time and space variations in the current field, current axis structures and main axis shift. Comparisons are made among the Kuroshio east of Taiwan Island, in the East China Sea, and the Kuroshio crossing the E section. Geostrophic transports are calculated. Second Inst. of Oceanogr., Natl. Bur. of Oceanogr., Hangzhou, People's Republic of China.

87:0031 Miyake, Hideo, Jiro Fukuoka and Noboru

Matsuura, 1986. Current measurement under the Oyashio First Branch southeast [of Hokkaido, Japan] off Erimo Cape. Bull. Fac. Fish. Hokkaido Univ., 37(1):58-68. (In Japanese, English abstract.) Res. Inst. of North Pacific Fish., Hok- kaido Univ., Japan.

87:0032 Pratt, L.J. and M.E. Stern, 1986. Dynamics of

potential vorticity fronts and eddy detachment. J. phys. Oceanogr., 16(6):1101-1120.

The formation and detachment of quasi-geostrophic eddies in a 1 ~/z-layer jet are studied using a piecewise uniform potential vorticity model. A vorticity front separates the two pieces, and thus the jet has a cusplike character. Certain numerical results such as the steepening of the front prior to eddy detachment can be physically explained in terms of differential mean field advection and vortex induction. Com- putations are made for a variety of initial conditions and we indicate the amplitude/scale conditions necessary for the detachment of an eddy. The discussion is directed to the problem of the formation of warm/cold rings in the Gulf Stream. Scripps Inst. of Oceanogr., La Jolla, CA 92037, USA.

87:0033 Reverdin, Gilles and James Luyten, 1986. Near-

surface meanders in the equatorial Indian Ocean. J. phys. Oceanogr., 16(6):1088-1100.

Drifting buoys released in the western Indian Ocean reveal meanders of the eastward flowing monsoon drift in August-September 1979, 1980 and 1981. Oscillating meridional buoy drifts reach 80 cm s 1 and meridional displacements can exceed 3 ° for motions at a period close to 25 days. In 1979, this is related to oscillations below the thermocline. It is likely that the origin of the oscillations is in the surface currents north of the equator. The currents

change in October with the formation of an intense eastward equatorial current in which most of the buoys are entrained. As the buoys drift rapidly toward the eastern Indian Ocean, meridional motions are still present but at shorter periods (12 days) than is observed below the thermocline (25 days). It is possible that this is still a manifestation of the same oscillations, but with Doppler shifting and a strong influence of nonlinearities. Waves at 25 days are found in the three oceans. LODYC, Unite Assoc. au CNRS, Paris, France.

87:0034 Schott, F.A., S.A. Frisch and J.C. Larsen, 1986.

Comparison of surface currents measured by HF Doppler radar in the western Florida Straits during November 1983 to January 1984 and Florida Current transports. J. geophys. Res., 91 (C7): 8451-8460.

While an earlier analysis of currents measured in summer 1983 (Schott et al., 1985) found significant northward shear in the northward radar currents about 20 km offshore, leading to concerns about a possible bias in the radar currents, this effect was not observed in the second application farther north. Concerning the usefulness of radar currents as Florida Current transport indicators, results are much more encouraging than the 1983 study. Florida Current transport fluctuations had a total range of 15 × 10 ~ mUs during the second observation period, and correlation with downstream radar currents, averaged zonally across the center of the radar field, was 0.85. Coherence was significant for periods longer than 5 days. Highest correlation with transport was found for radar currents farthest out, to the right of the axis of the stream. RSMAS, Univ. of Miami, FL 33149, USA.

g'/:0035 Stacey, M.W., Stephen Pond and P.H. LeBlond,

1986. A wind-forced Ekman spiral as a good statistical fit to low-frequency currents in a coastal strait. Science, 233(4761):470-472.

Ekman's classical analysis of wind-driven currents is a fundamental component of the modern circulation theory of the oceans, but there have been few good observations of the predicted Ekman spiral, where the velocity vector rotates clockwise (in the Northern Hemisphere) and decays exponentially in magnitude with increasing depth. An EOF analysis of recent cyclesonde velocity measurements suggests that a classical Ekman spiral was a good statistical fit to a significant portion of the low-frequency current fluctuations in the Strait of Georgia, British Colum- bia, for fluctuation periods of about 5 to 10 days. ®1986 by AAAS. Dept. of Oceanogr., Univ. of

OLR (1987j 34 (I) A. Physical Oceanography 7

British Columbia, Vancouver, BC V6T 1W5, Can- ada.

Al l0 . Water masses and fronts

87:0036 Oey, L.-Y., 1986. The formation and maintenance of

density fronts on the U.S. southeastern continental shelf during winter. J. phys. Oceanogr., 16(6): 1121-1135.

A cross-shelf and depth/time-dependent numerical model was used to study physical processes involved in the formation and maintenance of continental shelf density fronts; a model Gulf Stream and vertical mixing calculated according to a second- moment turbulence closure submodel are incorpo- rated. Results suggest that three or more winter storms are required to establish fronts on the midshelf; otherwise the front is located just inshore of, and may be indistinguishable from, the shelf- break front. Model simulations agree qualitatively with available hydrographic data. Skidaway Inst. of Oceanogr., Savannah, GA 31416, USA.

87:0037 Qiu, Daoli, Shilai Zhou and Changming Li, 1985.

Application of cluster analysis method in determining water-masses of the Huanghai Sea. Acta oceanoL sin. (English version), 4(3):337-348. Yellow Sea Fish. Res. Inst., Qingdao, People's Republic of China.

AI20. Convergences, divergences, upwelling

87:0038 Coste, B., A.F.G. Fiuza and H.J. Minas, 1986.

Hydrological and chemical conditions associated with the Portuguese coastal npwelling during late summer. Oceanologiea Aeta, 9(2):149-158. (In French, English abstract.)

The studied period corresponds to a weak upwelling phase with coastal displacement of offshore surface waters and progressive deepening of isopleths near- shore. Geostrophic computations indicate that the cross-shelf distribution of hydrographic properties is strongly controlled by a meridional current system (southward mesoscale jet over the slope and northward recirculation at more than 100 km offshore). Centre d'Oceanol, de Marseille, 13288 Marseille Cedex 09, France.

87:0039 McClain, C.R., S.-Y. Chap, L.P. Atkinson, J.O.

Blanton and Frederico De Castillejo, 1986. Wind-driven upwelling in the vicinity of Cape Finisterre, Spain. J. geophys. Res., 91(C7):8470- 8486.

Shipboard hydrographic and biological observations, wind data, and satellite-derived SST and pigment measurements are used to document upwelling evolution and subsequent coastal circulation related to wind events occurring over a 10-day period. Numerical simulations predict greatest upwelling either at Cape Finisterre or along the northern coast (as occurred during the observation period); combined with sea level data, results suggest northward-propagating wave disturbances traveling along the coast at speeds of 120-160 km/day. Lab. for Oceans, NASA Goddard Space Flight Center, Greenbelt, MD, USA. (slr)

87:0040 Rap, T.V.N., D.P. Rap, B.P. Rap and V.S. Raju,

1986. Upwelling and sinking along Visakhapat- nam [India] coast. Indian J. mar. Sci., 15(2):84- 87.

Stability and stratification of the water over the shelf disappear as cold saline waters characteristic of 60 m depth rise to the surface during March. Tilting of isopycnals and offshore displacement of isohalines suggest the surface divergence typical of a coastal upwelling driven by local wind stress. Upwelling is predominant off Visakhapatnam during premonsoon and monsoon periods. Natl. Inst. of Oceanogr., Andhra Univ., Visakhapatnam 530 003, India.

A150. Tides and sea level

87:0041 Bigg, G.R. and A.E. Gill, 1986. The annual cycle of

sea level in the eastern tropical Pacific. J. phys. Oceanogr., 16(6): 1055-1061.

The long period response of sea level on the eastern boundary of the Pacific separates, for linear dynamics, into a remotely forced part mainly due to zonal winds along the Equator to the west and a locally driven part where sea level slopes to balance the alongshore wind. Examination of the annual component of sea level on the eastern boundary indicates that the locally forced part dominates, whereas the remotely forced part plays a major role at semi- annual and interannual periods. Hooke Inst. for Atmos. Res., Univ. of Oxford, Clarendon Lab., Oxford OX1 3PU, UK.

8 A. Physical Oceanography OLR (1987) 34 (1)

87:0042 Fang, Guohong, Jingfei Yang and Xucai Zhao, 1985.

A numerical model for the tides and tidal currents in the Taiwan Strait. Aeta oceanoL sin. (English version), 4(2): 189-200.

Semidiurnal and diurnal tidal currents in the Taiwan Strait are computed simultaneously by using the finite difference method with two-dimensional nonlinear hydrodynamic equations. Agreement between the computed and observed results is satisfactory. Inst. of Oceanol., Acad. Sin., Qingdao, People's Republic of China.

87:0043 Li, Kunping, 1985. Low-frequency vibration spec-

trum of water level in the Bohai Sea. A cta oceanol, sin. (English version), 4(2): 169-179. First Inst. of Oceanogr., Natl. Bur. of Oceanogr., Qingdao, People's Republic of China.

87:0044 Molodenskiy, S.M., 1985. The dynamic theory of pole

tides. Phys. sofid Earth (a translation of Fiz. Zemli), 21(3):167-175.

Using a simple model of the ocean on a solid earth, a system of ordinary differential equations is obtained to establish estimates of the magnitude of the influence of inertia and bottom friction on tidal flow. (The effects of self-gravitation are not taken into account.) The value of the deviation of the pole tide from the static value depends upon the character of the depth distribution, the form of the shoreline, and the coefficients of bottom friction in general; the calculated deviation is quite small. It is further shown that bottom friction does not significantly alter the height of the pole tide, and that for the case of an ocean of constant depth and real distribution of land and sea, the reduction in the Chandler period is approximately 8 days. Shmidt Inst. of Earth Phys., Acad. of Sci., USSR. (hbf)

87:0045 Smith, N.P., 1986. The rise and fall of the estuarine

intertidal zone. Estuaries, 9(2):95-101.

Water level records from two sites in Indian River Lagoon, along Florida's Atlantic Coast, are used to characterize vertical displacement of the estuarine intertidal zone in response to subtidal frequency forcing. A 22-year water level record indicates that the seasonal cycle has a range approximately one-quarter greater than the mean tidal range. The intertidal zone thus rises and falls to such an extent that over time scales in excess of several weeks there is no layer which consistently experiences an alter- nating exposure and inundation. Unpredictable,

low-frequency water level fluctuations perturb this intertidal zone to such an extent that the proba- bilities of extreme high and low water levels, in addition to mean high and low water, must be determined to characterize the estuarine intertidal zone adequately. Harbor Branch Foundation, Inc., Box 196, Fort Pierce, FL 33450, USA.

87:0046 Thomson, D.J., L.J. Lanzerotti, UV. Medford, C.G.

Maclennan, A. Meloni and G.P. Gregori, 1986. Study of tidal periodicities using a transatlantic telecommunications cable. Geophys. Res. Letts, 13(6):525-528.

Determinations of tidal periods from spectral analysis of the voltage induced across an unpowered length of the TAT-7 telecommunications cable in the North Atlantic over ~19 days revealed prominent spectral components at several frequencies, including those identified as corresponding to the diurnal declination luni-solar, semidiurnal principal solar, semidiurnal principal lunar, and monthly lunar components. In addition, a large amplitude spectral component of high statistical significance was observed at a frequency of 3.0051 cpd, approximately one-third the sidereal day,

87:0047 Wong, K.-C., 1986. Sea-level fluctuations in a coastal

lagoon [Long Island, N.Y.]. Estuar. coast. Shelf Sci,, 22(6):739-752. Coll. of Mar. Studies, Univ. of Delaware, Newark, DE 19716, USA.

87:0048 Yu, Zhouwen, Anle Ye and Zongyong Chen, 1986.

Relation between daily mean sea level and tidal range and its preliminary dynamical explanation. Acta oceanol, sin., 5(2):157-164.

Data analysis reveals that both the daily mean sea level (obtained by averaging 24 hourly tide heights) and the daily mean tide range have an oscillation component with a period of 14.76 days, and that the coherence is very close to unity at this period. Besides the effect of Nyquist folding, radiation stress is regarded as the cause for the phenomenon. Shandong Coll. of Oceanol., Qingdao, People's Republic of China.

A160. Waves, oscillations

87:0049 Chen, Changsheng and Zenghao Qin, 1985. Dynamic

analysis of typhoon surges along the coasts of Zbejiang and Jiangsu provinces. Acta oceanoL sin.

OLR (1987) 34 (I) A. Physical Oceanography, 9

(English version), 4(4):515-526. Shandong Coll. of Oceanol., Qingdao, People's Republic of China.

87:0050 Elgar, Steve and R.T. Guza, 1986. Nonlinear model

predictions of bispectra of shoaling surface gravity waves. J. Fluid Mech., 167:1-18.

Boussinesq-type nonlinear equations for waves propagating over a sloping bottom accurately model the evolving bispectra of a spectrum of non-breaking shoaling surface gravity waves. Model response to a variation of the beach slope and the amount of nonlinear phase coupling in the initial conditions are also examined. The apparent unimportance of bottom slope motivates consideration of constant- depth KdV equations. Simple analytic solutions are found for harmonic growth in the special case of a monochromatic primary wavetrain. The associated bispectral evolution is qualitatively similar to field observations and to predictions based on the full Boussinesq model for a sloping bottom. Coll. of Engng., Univ. of Idaho, Moscow, ID 83843, USA.

87:0051 Holt, Benjamin and F.I. Gonzalez, 1986. SIR-B

observations of dominant ocean waves near Hurricane Josephine. J. geophys. Res., 91(C7): 8595-8598.

Radar images of ocean surface waves near Hurri- cane Josephine were acquired with the shuttle imaging radar system on October 12, 1984. Fast Fourier transform analyses reveal the presence of at least two dominant wave systems which undergo significant spatial variations in wavelength and direction. Jet Propulsion Lab., Calif. Inst. of Tech., Pasadena, CA 91109, USA.

87:0052 Miles, J.W., 1986. Resonant amplification of gravity

waves over a circular sill. J. Fluid Mech., 167:169-179.

The trapping of gravity waves over a circular sill, originally studied by Longuet-Higgins (1967), is re-examined. Explicit results obtained for resonance curves are in qualitative agreement with the corresponding shallow-water approximations of Longuet-Higgins, which have been questioned by Renardy (1983). A remarkably simple result is obtained for the mean-square response to a broad- band, randomly phased incident wave. Inst. of Geophys. and Planet. Phys., Univ. of Calif., La Jolla, CA 92093, USA.

87:0053 Shenoi, S.S.C. and C.S. Murty, 1986. Viscous

damping of solitary waves in the mud banks of Kerala, west coast of India. Indian J. mar. Sci., 15(2):78-83.

We present an analysis of wave damping in mud bank regions following the transfer of wave energy to the interior of the fluid column through the boundary layer; energy loss computations owing to viscous shear beneath the solitary wave over a smooth horizontal surface are also presented. It is shown that waves can almost or completely be dissipated over a mud bank about 3 4 km wide when the kinematic viscosity increases to 1 cm -~ sec '. Waves of higher amplitude are dissipated much faster than those of lower amplitude. Natl. Inst. of Oceanogr., Dona Paula, Goa 403 004, India.

87:0054 Sundar, V., 1986. Wave characteristics off the

southeast coast of India. Ocean Engng, 13(4): 327-338. Ocean Engng. Centre, Indian Inst. of Tech., Madras, India.

87:0055 Xiu, Richen, 1985. Propagation of tide wave in a

basin with variable cross-sectional area. Acta oceanol, sin. (English version), 4(1): 1-8.

With the WKB method an analytic solution of amplitude is obtained. It is found that the motion of a co-oscillating tide wave in a basin with variable cross-section is a progressive one, depending on the cross-section as well as on the frictional force. The effects of friction on tide wave motion are discussed in detail. First Inst. of Oceanogr., Natl. Bur. of Oceanogr., Qingdao, People's Republic of China.

AI70. Wind-wave interactions

87:0056 Mitchum, G.T. and A.J. Clarke, 1986. Evaluation of

frictional, wind-forced long-wave theory on the west Florida shelf. J. phys. Oceanogr., 16(6): 1029-1037.

Clarke and Van Gorder have recently formulated a model describing the large-scale, low-frequency response of continental shelf waters to synoptic-scale wind stress in terms of a sum of forced waves. Evaluation of the model using west Florida shelf data gave the following results. (1) The model successfully predicts both the coastal sea level and alongshore velocity component. (2) The west Florida shelf coastal pressure field is dominated by the first mode and can be understood as the sum of a forced

10 A. Physical Oceanography OLR (1987) 34 ( I )

wave which travels with the southward-propagating wind stress and a free wave generated at the Florida Keys. (3) Almost all the wind-induced energy on the west Florida shelf is due to the wind forcing acting on west Florida shelf waters. Hawaii Inst. of Geophys., Univ. of Hawaii, Honolulu, HI 96822, USA.

A180. Internal waves and tides

87:0057 Helfrich, K.R. and W.K. Melville, 1986. On long

nonlinear internal waves over slope-shelf topography. J. Fluid Mech., 167:285-308.

A generalized KdV equation, including the effects of nonlinearity, dispersion, dissipation and varying bottom topography, is formulated and solved nu- merically for single and rank-ordered pairs of solitary waves incident on the slope. Very good agreement between theory and experiment is obtained for a range of stratifications, topography and incident-wave amplitudes. Significant disagreement is found in some cases if the effects of dissipation and higher-order (cubic) nonlinearity are not included in the theoretical model. Weak shearing and strong breaking (overturning) instabilities are observed and found to depend strongly on the incident-wave amplitude and the stratification on the shelf. WHOI, Woods Hole, MA 02543, USA.

areas by means of current observations. A cta oceanol, sin., 5(2):165-172.

Based on the shear effect of internal wave currents in stratified fluid, the necessary condition for the possible existence of an internal wave and the sufficient condition under which there will be no internal wave are deduced starting from the continuity equation of incompressible fluid. The above two conditions are verified by the measured results from vertical current meter arrays at observation stations in the Bohai Sea and the South Huanghai Sea. First Inst. of Oceanogr., State Oceanic Admin., Qingdao, People's Republic of China.

87:0060 Shu, Xingbei, Junsheng Zhao, Zhenxiang Wang,

Hongliang Sun, Xuejun Gu and Shijiang Geng, 1986. Determination of the direction and velocity of internal tide waves by means of measurements at a single station. Acta oceanol, sin.. 5(2):173- 182.

In this paper, a method for determining the direction and velocity of internal tide waves is proposed, based on the continuity equation of incompressible fluids and taking the isotherm whose balance position is situated in the middle of the thermocline as the interface of a two-layer ocean. Calculated results agree fairly well with two sets of observations. First Inst. of Oceanogr., State Oceanic Admin., Qingdao, People's Republic of China.

87:0058 Henyey, F.S., Jon Wright and S.M. Flatt~, 1986.

Energy and action flow through the internal wave field: an eikonal approach. J. geophys. Res., 91(C7):8487-8495.

The energy and action flow through the small-scale part of the oceanic internal wave field is modeled using the eikonal technique, which is not subject to a weak interaction assumption. The action flows toward slightly higher frequency (and thus the waves gain energy), in striking contrast to weak interaction predictions of a strong frequency decrease. The energy dissipation scales with depth in agreement with measurements; the overall level is, however, a factor of 4 smaller. Possible sources of this dis- crepancy are discussed. Center for Studies of Nonlinear Dynamics, La Jolla Inst., CA 92037, USA.

A210. Ice

87:0061 Andree, Michael et al., 1986. Dating polar ice by ~4C

accelerator mass spectrometry. Radiocarbon, 28(2A):417-423.

Results of ~4C/~2C ratio measurements on CO: extracted from air bubbles in polar ice are presented. The samples investigated originate from the Dye 3, South Greenland, deep ice core and span approximately the last 10,000 years. The results are calibrated with tree-ring records. The J4C ages are compared with information obtained from seasonal variations of ice-core parameters and rheologic model calculation. Phys. Inst., Univ. of Berne, Switzerland.

87:0059 Shu, Xingbei, Shijiang Geng, Xuejun Gu, Hongliang

Sun, Zhenxiang Wang and Junsheng Zhao, 1986. Verification of internal waves in offshore

87:0062 Crabtree, R.D. and C.S.M. Doake, 1986. Raditr--echo

investigations of Ronne Ice Shelf [Antarctica]. Ann. Glaciol., 8:37-41.

OI .R { 1987} 34 ( t I A. Physical O c e a n o g r a p h > I I

A new, detailed map of the thickness of Ronne Ice Shelf has been produced, which agrees with an earlier version, but shows more structure in the northwestern part. In particular, major ice streams maintain their identity from sources such as Evans and Rutford ice streams all the way to the ice front. Regions where the ice shelf is locally grounded over Kershaw Ice Rumples and over more extensive ice rumples between Korff and Henry ice rises play a significant role in controlling the dynamics of the ice shelf. There is a possibility of extensive freezing-on of seawater under the thin, central section of Ronne Ice Shelf. British Antarctic Survey, Natural Environ. Res. Council, High Cross, Madingley Rd., Cam- bridge CB3 0ET, UK.

87:0063 Jeffries, M.O. and H.V. Serson, 1986. Survey and

mapping of recent ice shelf changes and landfast sea ice growth along the north coast of Eilesmere Island, NWT, Canada. Ann. Glaciol., 8:96-99.

Ground and aerial surveys along the north coast of Ellesmere Island confirm that a considerable area of shelf ice remains, although it is not as extensive as it once was due to periodic ice island calvings. However, the lost ice shelf is quickly replaced by landfast sea ice. The sea ice often persists for many years and thickens sufficiently to be considered as the restoration of former ice shelf. The landfast ice quickly assumes an undulating topography, similar to the ice shelves, the development of which is encouraged by melt water and wind action. Even under the present conditions of negative mass balance, the sea ice reaches considerable, unde- formed thicknesses. The thick sea ice forming today could be the precursor of an expansion of the ice shelves. Geophys. Inst., Univ. of Alaska, Fairbanks, AK 99701, USA.

87:0064 Lewis, J.K., R.D. Crissman and W.W. Denner, 1986.

Estimating ice thickness and internal pressure and stress forces in pack ice using Lagrangian data. J. geophys. Res., 91(C7):8537-8541.

A methodology is presented which allows one to calculate an ice thickness term using observed ice motion and wind data. Since the wind data can come from atmospheric pressure fields or numerical models, the methodology is in fact a remote-sensing capability which relies on ice motion data from satellite imagery, buoys drifting on the ice, etc. The thickness term is shown to be an effective ice thickness which reflects the strength of the ice as a result of the true ice thickness plus the added mass effect of the horizontal gradients of pressure and internal ice stresses. Examples of the temporal

variations of the effective ice thickness in the Beaufort Sea are presented. Science Applications Intl. Corp., College Station, TX 77840, USA.

87:0065 MacAyeal, D.R., S. Shabtaie, C.R. Bentley and S.D.

King, 1986. Formulation of ice shelf dynamic boundary conditions in terms of a Coulomb rheology. J. geophys. Res., 91(B8):8177-8191.

Coastal boundaries where fast flowing ice shelves shear past stagnant, grounded ice are typically riven with surface crevasses, seawater-filled basal crevasses, and tidal strand cracks. A boundary condition describing stress transmission through these fractured boundaries in terms of the Coulomb law is formulated; agreement between finite element simulations of the Ross Ice Shelf flow and field observations is improved over agreement obtained with formulations which do not account for ice failure. Dept. of the Geophys. Sci., Univ. of Chicago, IL, USA.

87:0066 Tomasson, H. et al., 1986. Proceedings of the

symposium on glacier mapping and surveying held at the University of Iceland, Reykjavik, 26-29 August 1985. Ann. Glaciol., 8:216pp; 46 papers.

Papers presented at the symposium and published here include various general treatments on the use of radio echo-sounding, aerial photogrammetry, the least squares method for reduction of theodolite measurements, Landsat photographs and digital data, Seasat range measurements, mass-balance measurements, application of mapping to water- power planning, the problem of 'hidden ice,' and cartographic methods for large-scale glacier maps. Geographic areas reported on, in addition to Iceland, are Canada, the United States, Norway, the Alps, Ellesmere Island, Greenland, Alaska, the Indus, the Himalayas, and Antarctica. (hbf)

87:0067 Wang, Renshu, Xushi Liu and Likun Zhang, 1985.

Numerical experiments of sea ice in the Bohai Sea. Acta oceanol, sin. (English version), 4(3): 349-358. Inst. of Mar. Environ. Protection, Natl. Bur. of Oceanogr., Dalian, People's Republic of China.

A260. Acoustics

87:0068 Adair, R.G., J.A. Orcutt and T.H. Jordan, 1986.

Low-frequency noise observations in the deep o c e a n . J. acoust. Soc. Am., 80(2):633-645.

12 A. Physical Oceanography OLR (1987) 34 ( I I

Simultaneous measurements of ocean-bottom infra- sonic and ocean-bottom and sub-bottom seismic noise in the frequency band 0.1-20 Hz are presented for 5.5-kin-deep water in the south central Pacific. In the band 0.1-1 Hz, noise propagation as seismic modes trapped in the seafloor is supported by observed spectral coherences, cross phases, and ratios between ocean-bottom pressure and vertical ground motion, and by the relatively lower noise levels in the borehole. Noise variations in this band are clearly correlated with changes in local wind direction and speed, presumably through ocean- bottom pressure fluctuations caused by nonlinear surface wave and swell interactions. Rockwell Hanford Operations, P.O. Box 800, Richland, WA 99352, USA.

87:0069 Belobrov, A.V. and I.M. Fuks, 1985. Short-wave

asymptotic analysis of the problem of acoustic wave diffraction by a rough surface. Soy. Phys. Acoust. (a translation of Akust. Zh.), 31(6):442- 445. Inst. of Radiophys. and Elect., Acad. of Sci. of the Ukranian, USSR.

87:0070 Bouvet, Michel, 1986. Expansions of the likelihood

ratio and applications. IEEE Trans. Acoust. Speech Signal Process., ASSP-34(4):653-660. CNRS, Univ. de Paris-Sud, 91190 Gif Sur Yvette, France.

87:0071 Brysev, A.P. et al., 1985. 'Giant' backscatter-ampli-

fication effect in the round-trip transmission of radiation through a rough surface. Soy. Phys. Acoust. (a translation of Akust. Zh.), 31(6):515- 516. Inst. of Gen. Phys., Acad. of Sci., USSR.

87:0072 Bunkin, F.V., G.A. Lyakhov and M.Yu. Romanov-

skii, 1985. Stimulated concentration scattering of sound in stratified liquid mixtures. Soy. Phys. Acoust. (a translation of Akust, Zh.), 31(6):446- 448. Inst. of Gen. Phys., Acad. of Sci., USSR.

87:0073 Dolin, L.S., A.M. Pavlenko, N.A. Sedunov and I.V.

Sheinferd, 1985. Characteristics of amplitude- modulated sound scattered by the sea surface. Soy. Phys. Acoust. (a translation of Akust. Zh.), 31 (6):489-490.

Information on the statistics of large-scale processes can be extracted from the fluctuation characteristics of the scattered modulated wave (MW) in the scattering of a sinusoidally intensity-modulated

wave by the indicated type of surface. The measurement of the characteristics of a reflected MW in the normal sensing of a rough surface makes it possible to determine the variance and correlation radius of large-scale irregularities; if the sensing takes place at small grazing angles, cross sections of the spatial spectrum of the large-scale roughness component can be measured over a wide range of spatial frequencies. An experimental study of this possibility is presented. Radiophys. Sci. Res. Inst., USSR.

87:0074 Eliseevnin, V.A., 1985. Response of a low-frequency

horizontal line array in free space and in a waveguide. Soy. Phys. Acoust. (a translation of Akust. Zh.), 31(6):491-492. N.N. Andreev Acoustics Inst., Acad. of Sci., USSR.

87:0075 Gorskaya, N.V., A.N. lvanov, V.V. Kurin, N.I.

Morozova and B.M. Salin, 1985. Phase relations for the propagation of a triharmonic wave in low-multimode acoustic waveguides. Sor. Phys. Acoust. (a translation of Akust. Zh.), 31(6):484- 486. N.I. Lobachevskii State Univ., Gorkii, USSR.

87:0076 Gostev, V.S. and R.F. Shvachko, 1985. Sound signals

observed in a geometrical shadow zone in the ocean. Soy. Phys. Acoust. (a translation of Akust. Zh.), 31(6):487-488.

The space-time and spectral characteristics of sound signals entering a geometrical shadow zone (GSZ) are investigated using spectral analysis of explosive signals corresponding to previously observed leakage and scattered signals in the GSZ; significant differences in their spectral composition are indicated. The spectra of the scattered signals are dominated by low-frequency components and the spectra are similar to the primary signal spectrum observed in the near field. The distinctive features of the leakage spectrum are readily explained by filter properties of the subsurface channel. It is hypothesized that appreciable sound scattering occurs in the vicinity of a caustic formed in the near sound field, which serves as the GSZ boundary, and the intensity maximum of the scattered sound is located in the direction of specular reflection from horizontally oriented finestructure inhomogeneities of the re- fractive index. N.N. Andreev Acoustics Inst., Acad. of Sci., USSR.

87:0077 Hanna, M.T. and Marwan Simaan, 1986. Array

filters for attenuating coherent interference in the

O L R (1987) 34 ( I ) A. Physical Oceanog raphy 13

presence of random noise. IEEE Trans. A coust. Speech Signal Process., ASSP-34(4):661-668. Dept. of Elect. and Comp. Engng., Univ. of Iowa, Iowa City, IA 52242, USA.

87:0078 Komissarova, N.N., 1985. Response of an array to a

sound field near a caustic. Soy. Phys. Acoust. (a translation of Akust. Zh.), 31(6):495-498. N.N. Andreev Acoustics Inst., Acad. of Sci., USSR.

87:0079 Kustov, L.M., V.E. Nazarov and A.M. Sutin, 1985.

Phase conjugation of an acoustic wave at a bubble layer. Soy. Phys. Acoust. (a translation of Akust. Zh.), 31(6):517-518. Inst. of Appl. Phys., Acad. of Sci., USSR.

87:0080 Meng, Jinsheng and Dinghua Guan, 1985. Esti-

mation of the attenuation of sound in marine sediments by normally-incident pulses. Acta oceanol, sin. (English version), 4(4):503-509.

A method of remote sensing of the attenuation of sound waves in marine sediments is proposed. Under certain conditions the echo envelope has an expo- nential decay which when the frequency is high enough would be the dominant factor in the shape of the echo envelope; therefore, the attenuation coefficient can be estimated from the envelope. The echo as a function of time is deduced on the basis of a small-scale layering model of marine sediments. The deduction can be regarded as a description of the mechanism of the volume-scattering of high-frequency sound in marine sediment. Experiments at sea are described, and the results are given. Inst. of Acoustics, Acad. Sin., Beijing, People's Republic of China.

87:0081 Ng, L.C. and Yaakov Bar-Shalom, 1986. Multisensor

multitarget time delay vector estimation. 1EEE Trans. Acoust. Speech Signal Process., ASSP- 34(4):669-678. Lawrence Livermore Natl. Lab., Univ. of Calif., Livermore, CA 94550, USA.

87:0082 Pavlov, V.I. and Yu. Slabeitsius, 1985. Nonlinear

attenuation of an acoustic wave packet propagating in a liquid near its disturbed free surface. Soy. Phys, Acoust. (a translation of Akust. Zh.), 31(6):504-505. M.V. Lomonosov State Univ., Moscow, USSR.

87:0083 Popov, V.V., 1985. Diffraction of a surface acoustic

wave in transition from a fiat zone to a rough zone of the surface. Sov. Phys. Acoust. (a translation of Akust. Zh.), 31(6):506-508. State Univ., Omsk, USSR.

87:0084 Qian, Z.W., 1986. Concentrated suspension theory of

sound attenuation in marine sediments: sound- and viscous-wave interactions. J. Sound Vibr., 108(1):147-156. Inst. of Acoustics, Acad. Sin., Beijing, People's Republic of China.

87:0085 Rubanov, I.L. and G.M. Sverdlin, 1985. Influence of

radiating channel failure on the parameters of an equidistant linear array. Soy. Phys. Acoust. (a translation of Akust. Zh.), 31(6):464-466. Ship- building Inst., Leningrad, USSR.

87:0086 Salomatin, A.S., V.P. Shevtsov and V.I. Yusupov,

1985. Sound scattering by the fine structure of hydrophysical fields in the ocean. Soy. Phys. Acoust. (a translation of Akust. Zh.), 31(6):467- 470.

It is shown on the basis of synchronous measurements of the backscattering of sound and hydrophysical parameters that the thin sound-scattering layers observed in the ocean are attributable to scattering at the boundaries of an abrupt variation of the sound velocity. Two-way diffusion processes play an important role in the formation of such layers. Pacific Ocean Oceanol. Inst., Acad. of Sci., USSR.

87:0087 Tolstoy, A., D.H. Berman, E.B. Wright and R.N.

Baer, 1986. A multibounce, single-scatter ray theoretic model. J. acoust. Soc. Am., 80(2):622- 632. Naval Res. Lab., Washington, DC 20375- 5000, USA.

87:0088 Vinitskii, S.I., I.V. Puzynin, T.P. Puzynina and S.Yu.

Slavyanov, 1985. Application of a continuum analog of Newton's method for calculating the guided-wave propagation of sound in the ocean. Soy. Phys. Acoust. (a translation of Akust. Zh.), 31 (6):478-479.

A number of conventional techniques for calculating eigenfunctions and eigenvalues of the boundary- value problem in a vertical cross section are inapplicable at frequencies of thousands of hertz. A continuous analog of Newton's method, developed

14 A, Physical Oceanog raphy Ot .R I 1987) 34 I I )

previously for application in quantum mechanical problems, can be used together with other standard methods as a possible algorithm for calculating normal modes. Among the advantages of this method are its applicability under liberal assump- tions about the behavior of the sound-velocity profile as a function of the depth, the possibility of checking the computational accuracy, the natural- ness of scaling the problem along a path with slowly varying parameters, and adequate speed. A.A. Zhdanov State Univ., Leningrad, USSR.

87:0089 Virovlyanskii, A.L., 1985. Temporal structure of a

pulse signal in an underwater sound channel. Soy. Phys. Acoust. (a translation of Akust. Zh.), 31 (6) :480-481.

Many modes of the underwater sound channel are excited when a sound pulse is transmitted in the ocean, producing at a reception point a super- position of wave packets, each 'transported' by its own mode. As a result of differences in the group velocities of the modes, differences in arrival times of the mode pulses grow with increasing range; their durations increase as the mode pulses spread. The possibility of the separate reception of these pulses is investigated by determining the relation of the parameters (pulse duration, carried frequency, course lengths, etc.) in order for a specific mode arrival to be discerned at the reception point. Inst. of Appl. Phys., Acad. of Sci., USSR.

A290. Physical processes, properties (diffusion, turbulence, etc.)

87:0090 Elliott, A.J., 1986. Shear diffusion and the spread of

oil in the surface layers of the North Sea. Dr. hydrogr. Z., 39(3):113-137.

Controlled releases of oil and dye to form slicks were observed for the six hours following release and compared with results of a numerical model which included vertical and lateral shears. The elongation and orientation of the modelled slicks were in good agreement with observations suggesting that near- surface vertical shears control the spreading rate of a slick soon after release. Numerical results showed that the major axis of the slick should elongate with time while width would grow as t °.5. In addition, the model correctly predicted the occurrence of thicker oil toward the leading edge and the alignment of slicks with wind direction. Unit for Coastal and

Estuarine Studies, Mar. Sci. Lab., Menai Bridge, Anglesey LL59 5EY, UK.

87:0091 Franz, Hjalmar and Holger Klein, 1986. Some

results of a diffusion experiment at a river plume front. Dt. hydrogr. Z., 39(3):91-112.

The fluorescent tracer rhodamine B was released at the light side of a river plume front with a strong salinity gradient. The whole rhodamine patch could not always be completely covered with ship sections due to the fast front-parallel spreading of the rhodamine. The extraordinarily high correlation between salinity and rhodamine concentration sug- gested that the rhodamine concentration be determined as a function of salinity (a conservative property due to its smaller gradients and fluxes). Thereby the large scale deformation of the water mass and the advective term of the transport equation are eliminated in first approximation. DHI, Berhard-Nocht-Strasse 78, 2000 Hamburg 4, FRG.

87:0092 Maxworthy, T., 1986. On turbulent mixing across a

density interface in the presence of rotation. J. phys. Oceanogr., 16(6):1136-I 137.

The entrainment rate at a density interface for Rossby number values of one and less, based on turbulent velocity and spatial scales, was measured. At small values of the Richardson number, rotation suppresses entrainment substantially, a result which can be understood qualitatively by considering a modification of the entrainment model of Linden. Dept. of Mech. and Aerospace Engng., Univ. of So. Calif., Los Angeles, CA 90089-1453, USA.

87:0093 Stacey, M.W. and L.J. Zedel, 1986. The time--

dependent hydraulic flow and dissipation over the sill of Observatory. Inlet [British Columbia]. J, phys. Oceanogr., 16(6):1062-1076.

Acoustic observations of streamlines and velocity were made near the sill crest during the summer of 1982, a time when freshwater runoff into the inlet had created a distinct surface layer. While the tide is accelerating, a simple, three-layer, hydraulic model accurately simulates the flow near sill crest. However once the tide begins decelerating the observed flow undergoes a transition which the three-layer model cannot explain. It is estimated that during the period of observation the hydraulic flow utilized only about 5% of all the energy removed from the barotropic tide. This suggests that other processes, such as the internal tide, are removing most of the energy from

OLR { 1987134 ( I ) A. Physical Oceanograph 3 15

the barotropic tide. Dept. of Oceanogr., Univ. of British Columbia, Vancouver BC V6T 1W5, Canada.

87:0094 Woods, J.D., R. Onken and J. Fischer, 1986.

Thermohaline intrusions created isopycnically at oceanic fronts are inclined to isopycnals. Nature, Lond., 322(6078):446-449.

Laboratory studies led to the idea that intrusions might be formed by double diffusion, in which case they would slope across isopycnals (surface of constant density). Observations of the structure of meandering fronts led to a different conjecture: that intrusions might be formed isopycnically by the ageostrophic circulation within unstable meanders on the frontal jet. Here we present first the observed structure of such an intrusion and then the results of a dynamical model simulating the isopycnic gen- eration mechanism at an unstable meandering front. We show that thermohaline intrusions formed isopycnically also slope across density surfaces, so there is no need to invoke double diffusion to explain such structures. NERC, Polaris House, North Star Ave., Swindon, Wiltshire SN2 1EU, UK.

A300. Fluid mechanics

87:0095 Caviglia, G. and A. Morro, 1986. Drag on a sphere in

a fluid. Nuovo Cim., (9)C(1):74-88.

The possible acceleration dependence of the drag on a sphere executing a translatory motion in a fluid is examined in detail. That the adoption of the scheme of incompressible fluids is crucial is made evident by showing that a striking contradiction would arise in compressible fluids. A procedure is applied which, in a suitable linear approximation, leads to an explicit expression for the drag in compressible fluids. The drag turns out to depend both on the present value and on the history of the speed of the sphere. Ist. di Matematica, Via L. B. Alberti 4, 16132 Genova, Italy.

87:0097 Chimonas, G., 1986. The combined Rayleigh, Kel-

vin-Helmholtz problem. Phys. Fluids, 29(7): 2061-2066.

Stability characteristics of a model tilted shear flow are studied. It is found that any tilt away from the strict Kelvin-Helmholtz situation destabilizes the flow, no matter how large the Richardson number. The transition from the Rayleigh limit to the Kelvin-Helmholtz limit proceeds smoothly, with the stability curves displaying a characteristic pattern of evolution. Sch. of Geophys. Sci.. Georgia Inst. of Tech., Atlanta, GA 30332, USA.

87:0098 Johnson, R.S., 1986. On the nonlinear critical layer

below a nonlinear unsteady surface wave. J. Fluid Mech., 167:327-351.

A theory of the nonlinear critical layer applicable to the far field of the surface wave is presented; this far-field region has the KdV equation as the leading approximation to the description of the surface wave. The asymptotic expansions valid in the layers above and below the critical layer are themselves expanded, permitting discussion of the manifestation of flow evolution over time, particularly in the formation of cats'-eyes, and the form taken by the vorticity. The aim is to provide as complete a theory as the Euler equations will allow. Sch. of Math., The Univ., Newcastle upon Tyne, NE1 7RU, UK.

87:0099 Luyten, J.R. and H.M. Stommel, 1986. Experiments

with cross-gyre flow patterns on a beta-plane. Deep-Sea Res., 33(7A):963-972.

Patterns of flow are computed in a two-layer, two-gyre ocean circulation model to demonstrate how the location of a localized region of buoyancy flux determines the nature of meridional and cross-gyre buoyancy transport. Problems of control of boundary conditions and location of shocks are discussed, using six examples. The calculation is carried out by the method of characteristics. WHOI, Woods Hole, MA 02543, USA.

87:0096 Chamberlain, J.A. and C.R. Carrigan, 1986. An

experimental investigation of convection in a rotating sphere subject to time varying thermal boundary conditions. Geophys. astrophys. Fluid Dynam., 35(4):303-327. Phillips Petroleum Co., John Adam St., London WC2N 6BW, UK.

87:0100 Merkine, L.-O. and Leonid Brevdo, 1986. Bound-

ary-layer separation of a two-layer rotating flow on a ft-plane. J. Fluid Mech., 167:31-48. Dept. of Math., Technion-Israel Inst. of Tech., Haifa 32000, Israel.

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Physical oceanography