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Unclassified SECURITYCLASSIFICATIONOFTHISPAGE REPORT DOCUMENTATION PAGE 1a.REPORTSECURITYCLASSIFICATION lb RESTRICTIVEMARKINGS Unclassified 2a.SECURITYCLASSIFICATIONAUTHORITY 3.DISTRIBUTION/AVAILABILITYOFREPORT Approvedfor publicrelease;distributionisunlimited. 2b.DECLASSIFICATION/DOWNGRADINGSCHEDULE 4.PERFORMINGORGANIZATIONREPORTNUMBER(S) 5 MONITORINGORGANIZATIONREPORTNUMBER(S) 6a.NAMEOFPERFORMINGORGANIZATION 6b.OFFICESYMBOL 7a.NAMEOFMONITORINGORGANIZATION NavalPostgraduateSchool (Ifapplicable) NavalPostgraduateSchool 35 6c.ADDRESS(City,State,andZIPCode) 7b.ADDRESS(Cry,State,andZIPCode) Monterey,CA 93943-5000 Monterey,CA 93943-5000 8a.NAMEOFFUNDING/SPONSORING 8b.OFFICESYMBOL 9.PROCUREMENTINSTRUMENTIDENTIFICATIONNUMBER ORGANIZATION (Ifapplicable) 8c.ADDRESS(City,State,andZIPCode) 10.SOURCEOFFUNDINGNUMBERS ProgramElementNo. ProiectNo. TaskNo. WorkUnitAccession Number 11.TITLE(IncludeSecurityClassification) SIMULATIONOFACOUSTICMULTIPATHARRIVALSTRUCTUREINTHEBARENTSSEA 12.PERSONALAUTHOR(S) Elliott,JohnM. 13a.TYPEOFREPORT 13b.TIMECOVERED 14.DATEOFREPORT(year,month,day) 15.PAGECOUNT Master'sThesis From To 1992,June 110 16.SUPPLEMENTARYNOTATION TheviewsexpressedinthisthesisarethoseoftheauthoranddonotreflecttheofficialpolicyorpositionoftheDepartmentofDefenseortheU.S. Government. 17.COSATICODES 18.SUBJECTTERMS(continueonreverseifnecessaryandidentifybyblocknumber) FIELD GROUP SUBGROUP AcousticTomography,OceanAcoustics,Oceanography,BarentsSea 19.ABSTRACT(continueonreverseifnecessaryandidentifybyNocknumber) InsupportoftheBarentsSeaPolarFrontExperiment(BSPPEX)inSeptember1992(BarentsSeaPolarFrontGroup, 1992),theplanned224Hz tomographysignaltransmissionsfromanearbottomsoundsourcetoaverticalreceiverarrayconsistingof16hydrophonesweresimulated. Acousticraysweretracedtothereceiverarrayatarangeof50kmusingtheNOAAHamiltonianRaytracingProgramfortheOcean(HARPO). InputtoHARPOwasamathematicaloceanenvironmentbasedonhistoricalbathymetricandsoundspeeddata. Acousticmultipatharrival structurewasconstructedthrougheigenraysearchesandestimationofraytubespreadingandsurfaceandbottomlosses. Aresolvabilityanalysis ofthesimulatedarrivalstructurerevealsthatthereareatotalof49uniqueresolvablerayarrivals. Amongthem,42arefromindividual omnidirectionalhydrophonesand7fromplanewavebeamforming. 20. DISTRIBUTION/AVAILABILITYOFABSTRACT 21 ABSTRACTSECURITYCLASSIFICATION El UNCLASSIFIED/UNLIMITED ] SAMEASREPORT ] OTICUSERS Unclassified 22a.NAMEOFRESPONSIBLE INDIVIDUAL 22b TELEPHONE(IncludeAreacode) 22c.OFFICE SYMBOL Dr.Ching-SangChiu 408-646-3239 OC/Ci DD FORM 1473.84 MAR 83APReditionmaybeuseduntilexhausted SECURITYCLASSIFICATIONOFTHIS PAGE Allothereditionsareobsolete Unclassified T2600A8 Approvedforpublic release; distribution is unlimited. SIMULATION OF ACOUSTIC MULTIPATH ARRIVAL STRUCTURE IN THE BARENTS SEA by John M. Elliott LieutenantCommander, United StatesNavy B.S., UniversityofFlorida, 1977 M.E., University ofFlorida, 1978 Submitted in partial fulfillment ofthe requirementsforthe degreesof MASTER OF SCIENCE IN PHYSICAL OCEANOGRAPHY MASTER OF SCIENCE IN ENGINEERINGACOUSTICS from the ABSTRACT In support of the Barents Sea Polar Front Experiment (BSPFEX) in September 1992 (Barents Sea Polar Front Group, 1992), the planned 224 Hz tomography signal transmissions from a near bottom sound source to a vertical receiver array consisting of 16 hydrophones were simulated. Acoustic rays were traced to the receiver array at a range of 50 km using the NOAA Hamiltonian Raytracing Program for the Ocean (HARPO). Input to HARPO was a mathematical ocean environment based on historical bathymetric and sound speed data. Acoustic multipath arrival structure was constructed through eigenray searches and estimation of raytube spreading and surface and bottom losses. A resolvability analysis of the simulated arrival structure reveals that there are a total of 49 unique resolvable ray arrivals. Among them, 42 are from individual omnidirectional hydrophones and 7 from plane wave beamforming. in 3(s>7 TABLE OF CONTENTS ................... I. INTRODUCTION 1 ........... A. OCEAN ACOUSTIC TOMOGRAPHY 1 B. BARENTS SEA POLAR FRONT EXPERIMENT 2 C. THESIS OBJECTIVES AND APPROACHES 6 D. THESIS OUTLINE 7 . . II. PHYSICAL OCEANOGRAPHY 9 A. INTRODUCTION 9 . B. WATER MASSES AND SURFACE WAVES 9 . C. BARENTS SEA POLAR FRONT 12 III. ACOUSTIC EFFECTS 15 A. INTRODUCTION 15 . B. ABSORPTION 15 C. SPREADING AND REFRACTIVE EFFECTS 15 . D. SURFACE LOSS 16 E. BOTTOM LOSS 18 IV. RAY THEORY ACOUSTICS 20 A. INTRODUCTION 20 B. HAMILTONIAN RAY TRACING 20 C. HARPO OVERVIEW 21 IV D. MODELING THE BARENTS SEA ACOUSTIC ENVIRONMENT 22 . 1. General 22 2. Sound Speed Field, Bathymetry, and Sea Surface 23 3. Summary 27 V. ARRIVAL STRUCTURE SIMULATION & ANALYSIS 29 A. INTRODUCTION 29 B. RAY PATH STRUCTURE 29 C. ARRIVAL STRUCTURE 30 D. ARRIVAL TIME STRUCTURE 32 E. RELATIVE AMPLITUDE 34 F. RESOLVABILITY ANALYSIS 39 1. Introduction 39 2. Method I - Individual Hydrophones 40 a. Time Analysis 40 b. a Analysis 41 t c. Resolvable Rays 43 3. Method II - Plane Wave Beamformer 46 VI. CONCLUSIONS 51 ' LIST OF REFERENCES 53 APPENDIX A: LIST OF EXTERNAL PROGRAMS 55 APPENDIX B: INDIVIDUAL HYDROPHONE RESOLVABILITY ANALYSIS TABLE 81 . APPENDIX C: LINE ARRAY RESOLVABILITY ANALYSIS TABLE 92 . . INITIAL DISTRIBUTION LIST 98 VI