Physical Oceanography (PO)

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https://hdl.handle.net/1912/7

Department members investigate the dynamics and thermodynamics of ocean circulation. They work globally from the Arctic to the Antarctic and from the Strait of Gibraltar to the Philippine shelf on the full range of oceanic processes, from mixing on centimeter scales to heat balance on the global scale.

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  • Technical Report
    Thermoconvective eddies in air : application to meteorology
    (Woods Hole Oceanographic Institution, 1939) Avsec, Dusan ; Ronne, Carl A.
    The object of the present work is a study thermoconvective eddies in a layer of air heated uniformly from below. Being given the importance that these eddies present in meteorlogical phenomena, we have tried to attain three principal objectives: 1. To realize systematic experiments on thermoconvective eddies in air under thicknesses exceeding considerably the scale generally employed by preceding experimenters; 2. To verify experimentally the practical value of the numerical results deriving from the theory of thermoconvective eddies; 3. To complete, by the results acquired in the course of our researches in the laboratory, the theory of thermoconvective eddies in the free atmosphere.
  • Book
    Vertical distribution of temperature and humidity over the Caribbean Sea
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1949) Bunker, Andrew F. ; Haurwitz, B. ; Malkus, Joanne Starr ; Stommel, Henry M.
    The observations presented and discussed in this paper were obtained as part of a research project conducted under contract NObs-2083 with the Bureau of Ships of the U. S. Navy by the Woods Hole Oceanographic Institution. The observations and their original reduction were carried out under the direction of Jeffries Wyman. The airplane soundings were undertaken by Kenneth McCasland and Alfred Woodcock. The sea surface temperature was measured on the surface ships by David F. Barnes and Roger Patterson. The necessary airplane (PBY-SA) and surface boats (PC's) were made available by the U. S. Navy. All observations were made during the spring of 1946 at about 19.5°N latitude, 66°W longitude, north of San Juan, Puerto Rico, and at about lO°N latitude, 79.5°W longitude, north of Coco Solo, Panama. An extensive preliminary report on the results of the expedition with a limited circulation was prepared by Wyman and his collaborators during the summer of 1946. The present paper deals with certain phases of the work in a more detailed fashion. Special attention is given to the temperature and humidity distributions in the vertical and to their interpretation in the light of meteorological principles. A discussion of atmospheric turbulence based on airplane measurements has already been published elsewhere (Langwell, 1948), and an application of the airplane soundings to the theory of cumulus clouds has been studied by Stommel (1947). The second and third chapters of this publication deal with the description of observational techniques used by the expedition, with the methods of reduction and present the data on which the later discussion is based. It has been thought desirable to publish these data in extenso because they may be of interest to other meteorologists in view of the sparsity of upper-air observations in this region. The actual preparation of Chapters II and III is largely the work of Bunker and Stommel. In order to show how the observations made off Puerto Rico fit into the general pattern of climatic and weather conditions in the Caribbean area Chapter iv presents a survey of the climate of this region and of the weather conditions during the time when the observations were taken. This Chapter was contributed by Joanne Malkus. It is pertinent to include in this general introduction the conclusion drawn in Chapter IV namely that the weather situations encountered represented, in general, a relatively undisturbed trade-wind regime of early spring. The homogeneous layer of nearly dry-adiabatic lapse-rate of temperature and almost constant mixing ratio is one of the most characteristic phenomena in the lowest atmosphere of this region. It is also of utmost importance for the energy budget of the hydrosphere and the atmosphere. Therefore, a special discussion of this layer by Bunker is given in Chapter V. Because of the nearly dry-adiabatic lapse-rate in the homogeneous layer most of the heat transfer between water and air in the trade-wind zone must be in the form of latent heat of vaporization, a conclusion whose thermodynamic implications were discussed thoroughly by Ficker (1936). For this reason the distribution of water vapor deserves special attention, and Chapter VI deals with this variable as a problem in turbulent mass exchange. The analysis presented in this chapter is due to Haurwitz and Stommel.
  • Book
    The sediments and stratigraphy of the East Coast continental margin : Georges Bank to Norfolk Canyon
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1949-08) Stetson, Henry C.
    The continental shelf off the northeastern coast of the United States was the first of our offshore coastal areas to be charted in detail by the Coast and Geodetic Survey, starting on Georges Bank in 1930. The techniques responsible for this increased accuracy in offshore waters were first described by Rudé (1938) and have been constantly improved. From these soundings Veatch and Smith (1939) compiled their set of contour charts aided by a grant from the Penrose Bequest of the Geological Society of America. These soundings reopened the submarine canyon problem first commented upon by Dana (1863), which had gradually lapsed into obscurity from insuffcient data. The reader is, of course, well aware of the major controversy, with all its far reaching implications, which has been precipitated since the 1930 surveys of Georges Bank were brought to the attention of geologists by Shepard (1933). As more of the new surveys were completed, data from the field sheets were kindly furnished by the U. S. Coast and Geodetic Survey to the Woods Hole Oceanographic Institution for use in dredging and coring operations. This field work, first reported in 1936, was continued from time to time until 1941 as new soundings became available. Rock dredging and coring has been carried out in every major canyon on the slope from Corsair Canyon at the tip of Georges Bank to Norfolk Canyon off the entrance to the Chesapeake (Fig. I). Numerous cores have also been taken from the areas in between; and while the whole slope from Georges to the Chesapeake has not been covered, it is believed that no significant areas have been missed. In fact, cores from the slope taken during the summers of 1940 and 1941 have yielded results that are corroborative rather than new. In 1938 on a cruise from Hudson Gorge to Norfolk Canyon, cores were taken on the slope in areas which Veatch had considered to be the most important (personal communication). In the following report the tows and cores will be described by areas from Georges Bank southwards, as the same region was revisited in successive years. The various samples, however, will be referred to by number followed by the year in which they were taken. The material is in storage in the Woods Hole Oceanographic Institution and in the Museum of Comparative Zoology at Harvard University. The late Joseph A. Cushman was kind enough to identify the Foraminifera which have been obtained in tows from the canyon walls and in cores, except for those described in Appendix A which is contributed by Fred B Phleger, Jr. Most of the type material is in storage in the Museum of Comparative Zoology, although at the present writing some is in the Cushman Laboratory in Sharon, Massachusetts. I am indebted to Lloyd W. Stephenson for identifying a molluscan fauna from one of the canyons, and to W. C. Mansfield who has reported on another formation. Numerous discussions with Percy E. Raymond have, as usual, proved most helpful, and thanks are also due to Eugenia C. Lambert for performing the mechanical analyses and to Constance French for other laboratory assistance. Phleger (1939, 1942, 1946) has previously published on the Foraminifera from the slope and deep water cores. This material is, at present, at Scripps Institution of Oceanography.
  • Book
    An electromagnetic method for measuring the velocities of ocean currents from a ship under way
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1950-03) Von Arx, William S.
    During the past four years a deliberate effort has been made at the Woods Hole Oceanographic Institution to devise methods of kinematic observation generally suited to the needs of oceanographers. One result of this work, the electromagnetic method, has been brought from the experimental stage to one of useful maturity. Many of the theoretical potentialities of the method are still to be explored and developed. Nevertheless it seems likely that this remaining work may be done more soundly if present developments of the theory and instrumentation are made available for use and evaluation by, others. These studies in methods of kinematic observation have been supported mainly under the provisions of Bureau of Ships Contract NObs-2083, and Office of Naval Research Contract N6onr-277-1. This support and the assistance of the Naval Ordnance Laboratory, the Hydrographic Office (Oceanographic Division), the United States Coast Guard, and the David Taylor Model Basin of the United States Navy is gratefully acknowledged.
  • Book
    The analysis of tidal phenomena in narrow embayments
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1950-07) Redfield, Alfred C.
    The tides of coastal embayments derive their energy from the ocean tides rather than from the direct action of lunar and solar gravitational forces. They are considered to be part of co-oscilating systems in which the period is determined by the tide in the outer sea, while the detailed character of the motion depends on the size and form of the enclosed basin (Defant, 1925; Doodson and Warburg, 1941). In narrow basins of simple form in which the influence of the earth's rotation is small, the motions resemble standing waves. Ideally, such waves are characterized by the simultaneous rise and fall of level on either side of a nodal line at which no change in elevation takes place. The elevation at high water increases with distance from the nodal line and slack water coincides with high and low water. The properties of tides due to standing waves may be deduced by assuming the motion to result from a primary progressive wave moving up the channel which undergoes complete reflection at a barrier. Mathematically, this situation may be treated as the interference of two identical progressive waves moving in opposite directions and so related that both waves are in phase at the barrier. This treatment of standing waves assumes the presence of total reflection, the absence of damping and the absence of effects of the earth's rotation. Since these conditions are not realized in natural tidal basins, the standing wave concept leads to oversimplification. In coastal embayments the most striking departure from the expectations of the standing wave concept is the discrepancy between times of high water and slack water, which may be great near the mouths of the larger bays and sounds. High water does not occur simultaneously within such enclosures but is earlier near the sea. Commonly, the nodal line is represented merely by a region in which the tidal range is small. These are effects which can be explained if damping of the primary and reflected waves by frictional or other effects is taken into account. According to these concepts, the problem of tidal behavior in embayments is to determine numerically the properties of the primary and reflected waves so as to account for the observed relations of amplitude and stream velocity of the actual tide and to correlate these numerical properties with the geographical form of the embayment. In the present paper an attempt is made to treat the tidal behavior in such a way that the observed changes in elevation and motion of the water along the path of the wave may be used to determine the distribution of phase of the primary and reflected waves along the channel and to measure the damping. The relations between the several aspects of a wave as it advances along a channel of uniform depth and width have been developed theoretically so as to show the times of high water and slack water, the range of the tide, and the phase relations of the primary and reflected waves along the channel for any degree of damping. By expressing the relationship of the several aspects of a reflected wave in a form in which the wave period is taken as the unit of time and distance is given in terms of the related phase changes, it is possible to eliminate the purely geographical dimensions and to obtain a wholly general description of the tide which may be used to indicate how any given channel distorts the behavior of the wave as it advances. In the case of irregular channels, in order to justify the application of relations deduced for uniform channels, in which the change in phase of the primary and reflected waves and their damping is proportional to the distance traveled and in which the velocity of the waves is constant, it is necessary to make the following assumptions: 1. That the effect of irregularities in cross section is to alter the velocity of the primary and reflected waves; i.e., to distort the geographical distribution of phase differences. 2.That damping is proportional to the phase change in the waves rather than to the distance traveled. 3. That the damping coeffcient, as defined, is constant along the length of the channel.
  • Other
    Indian Ocean Bubble
    (Woods Hole Oceanographic Institution, 195?-1960) Stommel, Henry M.
    The Special Committee on Oceanographic Research (SCOR) has endorsed an international cooperative program of oceanographic research and survey work in the Indian Ocean for the near future. 1961 is the year most often referred to. Although a number of features of the plans must necessarily be made on a high international executive level, it also seems desirable that oceanographers on a working level - who actually think they might be interested or involved in the work at sea - should exchange ideas and suggestions, and make tentative plans of just what they would like to try to do in the Indian Ocean. For this purpose, THE INDIAN OCEAN BUBBLE has been established, as an informal journal for exchanging views and ideas.
  • Technical Report
    A compilation of moored current meter observations : volume I
    (Woods Hole Oceanographic Institution, 1965-08) Webster, Ferris ; Fofonoff, Nicholas P.
    Summaries of current measurements made with Richardson current meters at three moored stations in the Western North Atlantic are presented. Averaged quantities are presented in the form of computer-plotted curves.
  • Technical Report
    A compilation of moored current meter observations volume II
    (Woods Hole Oceanographic Institution, 1966-11) Webster, Ferris ; Fofonoff, Nicholas P.
    Summaries of current measurements made with Richardson current meters at a group of moored stations near Bermuda, and at a single station south of Bermuda are presented. Averaged quantities are presented in the form of computer-plotted curves.
  • Technical Report
    A compilation of moored current meter observations volume III
    (Woods Hole Oceanographic Institution, 1967-11) Webster, Ferris ; Fofonoff, Nicholas P.
    Summaries of current measurements made with Richardson current meters in two regions of the Western North Atlantic are presented. Averaged quantities are presented in the form of computer-plotted curves.
  • Technical Report
    Air-sea interaction for the International Indian Ocean Expedition
    (Woods Hole Oceanographic Institution, 1968-02) Bunker, Andrew F.
    A C-54Q aircraft was bailed to the Woods Hole Oceanographic Institution to participate in the International Indian Ocean Expedition and other research projects in the fields of meteorology and oceanography. With the joint support of the Office of Naval Research and the National Science Foundation, the aircraft was modified and instrumented for meteorological research.
  • Technical Report
    Current measurements from moored buoys
    (Woods Hole Oceanographic Institution, 1968-03) Fofonoff, Nicholas P.
    Since January 1965,a program has been underway at the Woods Hole Oceanographic Institution, to measure currents at a limited number of fixed sites on a year round basis. Initially, one site was instrumented with both surface and subsurface moorings. The program has now been expanded to 4 major sites, extending along 70°W, from 39°20 ' N to the Hatteras Abyssal Plain at 30°N . In nearly three years of operation, a total of 65 moorings have been placed at the working sites, for periods up to six months. Recoveries from these sites have provided many velocity records of excellent quality. The repetitive exposure of moorings of essentially similar design under relatively standardized conditions has served to define clearly the design and operational problems that are inherent in such a program. A brief account is given of some of the problems encountered in routine buoy setting operations, and some of the results obtained from the measurements.
  • Technical Report
    Turbulence and turbulent fluxes over the Indian Ocean
    (Woods Hole Oceanographic Institution, 1968-09) Bunker, Andrew F.
    A C-54Q aircraft equipped with meteorological instruments was flown three times to India to participate in the International Indian Ocean Expedition. Flights were made out of Bombay, Gan, and Aden to observe winds, temperatures, humidities, clouds, radiation, carbon dioxide, tritium, turbulence, and turbulent fluxes of heat, water vapor, momentum and kinetic energy. The present paper reports the values of 405 measurements of the turbulence and turbulent fluxes and interprets them in terms of the monsoon circulation and the effect upon currents and temperatures of the Arabian Sea. Analyses of other data have been reported and interpreted elsewhere. The aircraft turbulence measuring system used was developed earlier by Bunker (1955) (1960). It consisted of a vertical accelerometer, a strain-guage air-speed transducer, a vertical gyro, a platinum wire thermometer and a microwave refractometer for humidity measurements. The data was recorded on a nine-channel oscillograph. A digitizing reader was used to read and punch the data on cards. The turbulent quantities and fluxes were computed and tabulated by machine. The accuracy and limitations of the system are discussed. While much is left to be desired in terms of accuracies and spectral range, the results are meteorologically useful and comparison shows good agreement with other techniques.
  • Technical Report
    Summary of current meter operations in 1968
    (Woods Hole Oceanographic Institution, 1969-03) McCullough, James R. ; Tupper, George H.
    This report describes work done with Geodyne current meters and wind recorders during 1968. Techniques for testing instruments prior to use at sea, instrument performance at sea and instrument changes evolved during the year are discussed.
  • Thesis
    Inertial oscillations in the Mediterranean
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1970-06) Perkins, Henry T.
    Measurements of ocean currents were made by the author in the Western Mediterranean Sea at five depths for two months during early 1969. In terms of the dominant and persistent presence of inertial oscillations, circularly polarized currents having periods of a half pendulum day, the data are among the most striking ever collected. Two contemporary theories have been adapted for interpretation of this data. On the basis of a ray or short-wave-length theory, energy arriving at the observing site is found to fall into two categories, that making direct arrival from the, surface where it is assumed to have been generated, and that which undergoes one or more reflections. To the extent that the former dominates, it is found that the Algerian Coast about 130 km. to the south would cast a shadow to the north, the precise shape of which would be highly dependent on small variations in frequency. The nature of this frequency dependence implies a gradual increase in frequency with depth at the observing latitude. Although the data show a measurable shift (about 3%) towards higher frequencies, which is roughly the required amount, the lack of progressive frequency change with depth does not support the shadow hypothesis. In addition, the data is interpreted in terms of normal mode theory, where the nearby coast is seen to force a discrete modal structure to the solutions. The observed variation of current phase with depth indicates that a single internal mode dominates over a large portion of the data, while variations of both current amplitude and phase with depth are consistent this being the third internal vertical mode. Existence of a normal mode is also consistent with the long time, on the order of three weeks, for which the oscillations were observed to persist and with the dimensions of the Mediterranean Basin.
  • Thesis
    Experimental study of internal gravity waves over a slope
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1970-09) Cacchione, David A.
    A series of laboratory experiments were conducted in a glass wave tank to investigate the propagation of internal gravity waves up a sloping bottom in a fluid with constant Brunt-Vaisala frequency. Measurements of the wave motion in the fluid interior were primarily taken with electrical conductivity probes; measurements in the boundary layer were made with dye streaks and neutrally buoyant particles. The results indicate that, outside of the breaking zone, the amplitude and horizontal wave number of the high-frequency waves increase lineariy with decreasing depth; this is shown to agree with existing linear, inviscid solutions. A zone of breaking or runup is induced by these high-frequency waves well upslope. Shadowgraph observations show that, if the wave characteristics are coincident, or nearly so, with the bottom slope, the upslope propagation of the low-frequency waves causes a line of regularly spaced vortices to form along the slope. Subsequent mixing in the vortex cells creates thin horizontal laminae that are more homogeneous than the adjacent layers. These laminae slowly penetrate the fluid interior, creating a step-like vertical density structure. Available linear theoretical solutions for the velocity in the viscous boundary layer, determined to be valid for certain experimental conditions, are used to develop a criterion for incipient motion of bottom sediment induced by shoaling internal waves. The maximum sediment sizes that can be placed into motion, according to this criterion, are larger than certain mean sediment sizes on the continental margin off New England. This suggests that internal waves might induce initial sediment movement. Speculation about the geological effects of breaking and vortex instabilities is also given. These processes, not definitely measured in the field as yet, might also be conducive to sediment movement.
  • Thesis
    Shear of small vertical scale observed in the permanent oceanic thermocline
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1971-01) Van Leer, John Cloud
    Two shear experiments performed in the permanent thermocline are described and analyzed in this thesis. The first employed dye streak techniques to gain fractional meter vertical resolution. Shears with small vertical scales with frequent reversals in direction and changes of magnitude were observed in every experiment between 160 and 900 meters depth. The ratio of the standard deviation of shear magnitude to the mean shear magnitude was computed at the depth of each dye experiment. These ratios decreased exponentially with depth suggesting a decay of surface supplied energy. The vertical wave number of the shear is not inconsistent with high mode inertio-gravitational internal waves or interleaving layers or salt-driven convection. The second experiment used sensor pairs to measure shear, temperature gradient, and salinity gradient with three meter vertical spacing. A weak but significant negative correlation between shear magnitude and density gradient magnitude was found in most of the records whether density gradient was computed from temperature and salinity or estimated from temperature alone. This result disagrees with a simple linear internal wave model developed for a layered medium. The expected positive correlation is strong enough to cause shear instability to occur first in regions of strongest static stability. This prediction again disagrees with observed shear density data in which the smallest Richardson numbers occur in weakly stratified regions. This negative correlation was observed to be strongest in regions of weak static stability. Perhaps we are observing the results of mixing processes in the main thermocline which cannot be described by the simple linear equations of motion. Two likely sources for the energy of mixing are suggested. Inertial motions are shown to have sufficient energy at thermocline depth and are known to have high enough vertical wave number to have shears comparable to those observed. Salt fingers are known to be able to release enough energy from an unstable salt buoyancy field to form convective layers under laboratory conditions. Since the temperature and salinity in the main thermocline near Bermuda both decrease with depth and have nearly equal and opposite buoyancy contributions, salt fingers must be considered likely. In the main oceanic thermocline no single mixing process seems likely to dominate everywhere or perhaps anywhere. The data collected in this thesis and elsewhere are not yet sufficient to define the statistics of these mixing processes or even to uniquely separate one from another at one location. A time series of experiments combining the two techniques developed in this thesis should be able to establish how shears vary in direction with time and vary with density gradient. These questions are at the heart of the thermocline mixing problem.
  • Thesis
    The influence of topography on steady currents and internal waves
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1971-01) Hogg, Nelson G.
    Observations of the ocean in the vicinity of Bermuda on two different occasions show systematic distortions of the isotherms close to the island and an area of intensive mixing on the northern coast. Two mechanisms are investigated and each produces some agreement with data from different flow regimes. Firstly, the island is modeled as a circularly symmetric obstacle with steep sides and a small aspect ratio. A steady, rotating, and stratified flow which, far from the island, is uniform in the horizontal and a linear function of the vertical coordinate is taken to be flowing past the island. Neglecting circulation effects, the problem is solved to first order in a small parameter, α, which measures the steepness of the island and a small Rossby number, ε. This allows a calculation of the depth contours of isotherms to 0(ε2,εα). For one set of data the flow is such that the slope effect of 0(εα) predominates while for another period of observation both slope and Rossby number influences are of the same magnitude. In both cases qualitative agreement between fact and theory is remarkably good. In addition, it is shown that the north slope (for a west-east current) is the most favored area for mixing as there the Richardson number is a minimum and the flow is most likely to separate from the boundary. A second means of producing isotherm distortion and mixing areas close to the island concerns the nonlinear effects of shoaling internal gravity waves. For normal incidence on a two-dimensional beach the Reynolds stresses produced by the fundamental wave motion are shown to force a mean Eulerian current which is equal hut opposite in sense to the Stokes drift. This causes the mean Lagrangian current to vanish so that the physical constraint that there be no net motion of fluid particles along isopycnals into the beach is satisfied. In addition, isotherms are distorted in a fashion analogous to the surface set-down produced by shoaling surface waves. The mean isopycnal shift can be as much as 10m where the theory has some validity. Distortions of the predicted form are observed in the data from a period when the mean currents were small. Consideration of the oblique incidence problem shows that this generalization has little effect on the expected magnitude of the shifts but that a significant longshore current can be forced by the breaking of the waves.
  • Thesis
    On the flow induced in a thermally stratified fluid by a source of heat
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1971-06) Knox, Robert A.
    The flow produced by an infinitely long horizontal heated strip in a thermally stratified fluid is examined theoretically. For strong stratification a long flat convection cell or tongue results. Profiles of velocity and temperature anomaly are displayed and contrasted with the profiles which would obtain if the temperature anomaly were only a passive tracer. The effects of small nonlineari ties are computed by perturbation methods and the profile alterations thus produced are discussed. A laboratory experiment set up to demonstrate the major features of this circulation is described. Qualitative agreement between theory and experiment is obtained, and certain of the predicted nonlinear effects are observed.
  • Technical Report
    A compilation of moored current meter and wind observations : volume V (1966 measurements)
    (Woods Hole Oceanographic Institution, 1971-07) Tarbell, Susan A. ; Webster, Ferris
    Summaries of wind and current measurements made with current· meters and wind recorders by the Woods Hole Oceanographic Institution during the year 1966 are presented. Averaged quantities are presented in computer generated output as histograms, basic statistics, spectra, progressive vector diagrams, and east-north component plots.
  • Thesis
    Experiments in a rotating source-sink annulus
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1971-08) Ingram, Richard Grant
    An experimental investigation of the different flow regimes in a rotating source-sink annulus is described. Both the steady and transient velocities are measured over a large range of Ekman Reynolds number and Rossby number. Differing probe configurations are used to investigate the corresponding motions in spatially separated regions of the annulus. The steady interior circulation field exhibits a strong dependence on the imposed flux values. The non-dimensional circulation increases with radius over a certain radial range for higher system Rossby number. The observed profile changes are related to the existence of an unstable Ekman layer at some inner radial position. The thickness of the observed Ekman layers is typically 85% of the theoretical scale height. For higher local Reynolds number (ReL), the thickness is generally much smaller. The width of the sidewall boundary layer adjacent to the sink increases with larger system Rossby number. Adjacent to the source, the radial boundary layer is wider than that at the sink wall. Observed oscillations are separable into three types. For ReL > 50, instability waves are observed in the Ekman layer flow. In the same Re range, inertial oscillations are detected in the interior region of the annulus. The observed inertial wave frequency at differing radial positions is explained by incorporating Doppler shift corrections and taking account of the steady circulation profiles. The radial wavelength of the inertial waves corresponds to the length of the Class A Ekman layer instabi1ity. For small values of Re and local Rossby number, an axisymmetric disturbance, with a characteristic frequency slightly greater than therotation rate, is observed at the outer radial positions.