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Meeting Abstracts Downloaded from orbit.dtu.dk on: Oct 08, 2021 Nonlinear acoustics of water-saturated marine sediments Jensen, Leif Bjørnø Published in: Acoustical Society of America. Journal Link to article, DOI: 10.1121/1.2003625 Publication date: 1976 Document Version Publisher's PDF, also known as Version of record Link back to DTU Orbit Citation (APA): Jensen, L. B. (1976). Nonlinear acoustics of water-saturated marine sediments. Acoustical Society of America. Journal, 60(Suppl. 1), S96-S97. https://doi.org/10.1121/1.2003625 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. PROGRAM OF The 92nd Meeting of the AcousticalSociety of America Town and Country Hotel ß San Diego, California ß 15-.19 November 1976 TUESDAY, 16 NOVEMBER 1976 SENATE/COMMI'ITEE ROOM, 8:30 A.M. SessionA. PhysicalAcoustics I: AtmosphericAcoustics ! EdmundH. Brown,Chairperson WavePropagation Laboratory, NOAA, Boulder,Colorado 80302 Invited Papers 8:30 A1. Contributionsof acoustic echo soundingto atmospheric research and services. C. Gordon Little (Wave Propagation Laboratory, NOAA, Boulder, CO 80302) This paper reviews briefly the first few years of acoustic remote sensing'that followed the introduction of the echosonde in 19fi6, and then surveys in more detail many aspects pt recent developments in acoustic echo sounding. The early, qualitative, facsimile recordings 'save now been supplemented by attempts to make the echosoude data quantitative. This has 'n- volveal careful cornparian of data from calibrated sounders and instrumented meteorlogical towers. Evidence is presented supporting the claim that echosondes can supplement the facsimile records with height profiles of mean wind speed and direction, as well as pn)files of the structure constantof velocity C, and temperature Cr. The former permits derivation of the height profiles of the turbulent energy dissipation rate ½ and the latter the measurement of heightprofiles of the structureconstant of optical refractive indexC a. Various rear.zations of Doppler echosondesare presented, together with an echosonde interferometer which may offer promise of measuring atmospheric temperature profiles. Some future directions for acoustic echo-soundingdevelopments are summarized. Contn'butedPapers 9:00 9:15 A2. Acoustic soundingof atmospheric winds. D.R. Jensen and A3, Acoustic wind and wind-shear measuring system. P.A. J.H. Richter (Naval Electronics Laboratory Center, 271 Cata- Mandies and D.W. Betart (Wave Propagation Laboratory, En- lina Bird,, San Diego, CA 92152) vironmental Research Laboratories, National Oceanic and Atmospheric Administration, Boulder, CO 80302) Acoustic echo sounders have recently come into their own as valuable remote sensors for determining atmospheric struc- An acoustic wind-profiling system designed to detect hazard- tures and winds. Kelton and Bricout [Bull. Am. Meteor, Soc. ous wind-shear conditions in the airl•)rt environment has been 45, 571--580 (1964)] first demonstratedthat the acoustic Dop- developed during the past four years. The system installed at pler shifted signals from scattered soundwere related to the Dulles International Airport consists of a vertically pointed ambientwinds, Later, McAllister [J. Atmos. Terr. Phys, transmitter surrounded by three receivers 290-m distant and 30, 1439--1440 (1968)] showedthat a vertically pointingmono- separated by 120' in azimuth. Electr½,nically steered receiver static acoustic sounder could reveal, in intricate detail, the beams track the upward propagating transmitted tone burst and atmospheric boundary layer structure. An acoustic echo sound- collect the scattered acoustic signals. The Doppler frequency er and wind sensor system capable of simultaneously measur- shift of the returns is analyzed digitally to determine the hori- ing temperature fluctuations in the lower atmosphere and the zontal wind at 20 height levels in 30-rs increments. Unique vertical profile of wind speed and direction has been in opera- design features of the system such as the steered receiver tion at the Naval Electronics Laboratory Center since 1973. antenna are described. A one-leg prototype of the Dulles sys- It is the purpose of this paper to describe the capability of this tem was installed and tested at Table Mountain near Boulder, acoustic echo and wind sensor system for determining atmo- CO. Winds measured by the prototype acoustic system com- spheric structure and winds. pared well with those determined by an FM-CW radar and a Sl J. Acoust.Soc. Am., Vol. 60, Suppl.No. 1, Fall 1976 Copyright¸ 1976by the AcousticalSociety of America S1 S2 92ridMeetinfo: Acoustical Society of America S2 balloon-borne anemometer. Noise generated by v:Hn und sur- cal thickness of the plume w.s as ].rge as that assumed in the face windsexceeding 16 msec-I l)roved to be the major limita- plume rise theory (namely, vertical thickness cOral)arableto tions for the acoustic system. Preliminary results from the mean plume height above stack top). 11eighispredietcd using Dulles system are also presented. standard plume rise theory, with mete..Iogical inputs extra- polated from surface observations rather th:m being measured aloft, were subst•mtially lower Ih;m the observed heights. The 9:30 plume lurbulenee and temperature gave sufficient acoustic A4. Acousticecho sounding of the marine boundarylayer. V. I/. scattering when the plume was nea. the linal I)lume hcig'ht (about 150 m) to avoid confusion with cchocs from the ambient Noonkester, D.R. Jensen, and J.H. Richter INaval Electron- ies Laboratory Center, 271 Catalina Blvd., San Diego, CA atmosphere. 92152) 10: I 5 Acoustical probing of the lower atmosphere has proliferated since 1968 when McAllister [3. Atmos. Terr. Phys. 30, A7. Analytical studiesof sodarohscrxutions at l)elhi. S.P. Singal, N.N. Datta, B.S. (;era, S.K..\ggat'wal(National 1439--1440 (1968)] demonstrated its advantages. Considerable Physical Laboratory, New 1)clhi--110012, India). acoustic echo soundingshave been made in conlinental regions but echo soundingof the marine boundary layer IMBL} is A monostatic sodar system has been operating at the National fragmentary. Many hours of acoustic echo-sounding data have Physical Laboratory, New Delhi 128.6'N, 77.2øEl since I)e- been taken since 1974 at a multisensor site on the Pacific coast cember 1974. Echograms obtained up to May 1976 (operational in San Diego, CA, where the prevailing northwesterly winds period of approximately 1500 h) have been qualitatively ana- carry the MBL over the echo sounder almost continuously. lyzed with respect telheir structural details. Layers are a Simultaneous observations of the MBL by the echo sounder, general feature of the sodar echogr:•ms•ilh their thickness other surface-based remote sensors (e.g., FM-CW radar and lying mostly within 20 m. Their percentage occurrence lidar) and standard meterological sensors (e.g., radiosondes) reaches a maximum of 95% between 1600--2000 h and a minima have aided in the interpretation of the echo-sounder data. of 40% between 1200--1400 h, The height oflhe layers has a These observations have been augmented by observations on primary maximum (average height 220 m and maximum height the Atlantic coast near Wallops Ishmd, VA. The paper will 350 m) between 0200--0400 h, a minimum (average height 175 present some characteristic echo-sounder data o[ the MBL m) between 0800--1000 h .'red a secondary maximum (average with meterological interpretations. height 190 m) between 1100--1400 h. Turbulence is a very characteristic observatien under stable eenditions and is pres- 9:45 ent for about 1:1%of the time. The turbulent as also the layer structures have been classified into w•rious categories aeeord- A5. Acoustic soundingof the tropical marine boundary layer ingto their typical fcalures. 1)iseernible thermal plume struc- during GATE. P.A. Mandies, J.E. Gaynor, and F.F. Hall, tures have been rarely seen over Delhi. The structure is most- Jr. (Wave Propagation Laboratory, l•:nvironmental Research ly affected by the prevalent ambient wind. The convective ac- Laboratories, National Oceanic and Atmospheric Administra- tivity is maximum around 1200--1400 b. tion, Bouhter, CO 80302) A vertically pointed monostatic acoustic sounder was in- 10:30--BREAK stalled on the NOAA Ship OCEANOGRAPHER during the Global Atmospheric Research Program Atlantic Tropical Experiment 10:45 (GATE). The sounder antenna was mounted on a gyrocontrolled A8. Near-horizontal propagationof soundover grassland. •. E. platform to compensatefor the ship's pitch and roll motions. Pierey, R.J. Donate, andT. F.W. Embleton (Division of Extensive measures such as mounting the antenna assembly on Physics, National Research Council, Ottawa, Ontario, Canada a vibration isolator and installing absorbing cuffs had to be K1A OS1) taken to reduce interference by ship-generated noise. Back-
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