## TOWAN httpwww7180nrlsscnavymilhomepages TOWANtowanpgsTOWANData Indexhtml

The US Navy Tactical Oceanography Wide Area Network (TOWAN) is a data server dedicated to supplying the DOD and supporting contractors with environmental data for simulation, modeling and other analyses. The purpose of TOWAN is to provide rapid sub-setting and data extractions from existing databases, and to deliver the extracted data using a consistent and documented output format. It is not the intent of TOWAN to merge datasets or do any interpolation on the data extracted. The contents of...

## Info

-20 -15 -10 -5 0 5 10 15 20 Doppler (ms-1) -20 -15 -10 -5 0 5 10 15 20 Doppler (ms-1) Figure 9.7 Example from the REVMOD reverberation model showing the surface-scattering function for a downwind case. (Hodgkiss, 1984 IEEE J. Oceanic Eng., 10, 285-9 copyright by IEEE.) were 102 and 86 ms, respectively. See Ziomek (1985 chapters 3 and 4) for a discussion of complex apertures and directivity functions. The Doppler of the surface component of the scattering function reflects a complex interaction...

## Hbem Hfbl

FEPE with Conformal Mapping Finite-Element Parabolic Equation Model with Shear-Wave Effects Fast-Field Program Finite-Element, Full-Wave Range-Dependent, Acoustic Marching Element Model Fast Fourier Transform Federal Information Processing Standards Floating Instrument Platform Fast Linear Intermediate Range Transmission Model Oceanography Center (formerly FNOC) Fast Normal Mode with Surface Scattering Integrals Model Fleet Numerical Oceanography Center (now FNMOC) Finite-Element Ocean Acoustic...

## V

T +--T- + - + --+ k2n2 V Using kjo as a separation constant, separate Equation (4.21) into two differential equations as follows which is the zero-order Bessel equation, and + 1r2 + + + k2n2V - k2v 0 (4.25) The solution of the Bessel equation (4.24) for outgoing waves is given by the zero-order Hankel function of the first kind For k0r 1 (far-field approximation)

## Operational oceanography

The term operational oceanography has become a topic of frequent discussion in the contemporary trade literature, although the activities normally associated with this term have been in existence for some time. The three principal attributes that characterize operational oceanography are (1) routine and systematic measurements of the oceans and atmosphere (2) modeling, simulation, analysis and interpretation of these measurements to generate useful information products and (3) rapid...

## S V nL expt kor

Which is the asymptotic expansion for large arguments. The equation for V(r,z) Equation (4.25) can then be simplified to + + 2k017 + k0 (n2 - 0 V 0 (4.28) which is the paraxial approximation. Then, Equation (4.28) reduces to + 2ik0 + k2 (n2 - 1) V 0 (4.30) which is the parabolic wave equation. In this equation, n depends on depth (z), range (r) and azimuth (0). This equation can be numerically solved by marching solutions when the initial field is known (e.g. Tappert, 1977). The computational...

## Tdpa

Time-Domain Parabolic Approximation Model Time-Domain Parabolic Equation Target Echo, Noise and Reverberation Tactical Environmental Support System Turbulent Kinetic Energy Transmission Loss Transmission Line Matrix Modeling Netherlands Organization for Applied Scientific Research Total Ownership Cost Topography Experiment for Ocean Circulation (unflown NASA precursor mission to TOPEX Poseidon) TOPEX Poseidon Joint US-French orbital mission launched in 1992 to track changes in sea-level height...

## Jr

Where Dtra 20logj0 dtra is the reference level of the transmitting array, p1 20logj0 p1l the transmission loss of the incident ray, Figure 10.3 Closed ray path used in reverberation calculations in the NISSM active sonar model (Weinberg, 1973). Figure 10.3 Closed ray path used in reverberation calculations in the NISSM active sonar model (Weinberg, 1973). Figure 10.4 Ensonified region used in reverberation calculations in the NISSM active sonar model (Weinberg, 1973). Figure 10.4 Ensonified...

## Navmsmo httpnavmsmohqnavymil

The US Navy Modeling and Simulation Management Office (NAVMSMO) maintains the Navy Modeling and Simulation Catalog, which allows users to find and obtain M& S resources in support of analyses and training. The NAVMSMO web site serves as the web-enabled single point of public access to the Navy's M& S Information Service (NMSIS). The NMSIS collects, maintains and distributes information about Navy modeling and simulation for the use of program managers, engineers, M& S builders and...

## OALIB httpoalibsaiccom

The Ocean Acoustics Library provides access to some of the stand-alone propagation models reviewed in this book. This access is provided directly to downloadable software or indirectly by reference to other authoritative websites. The Ocean Acoustics library contains acoustic modeling software and data. It is supported by the US Office of Naval Research (Ocean Acoustics Program) as a means of publishing software of general use to the international ocean acoustics community. Table C.1 summarizes...

## Marsh And Shulkin

Figure 5.8 Downslope propagation over a constant 5 slope. Results were generated using a PE propagation model (Jensen and Schmidt, 1984). Two noteworthy empirical algorithms have been developed for use in predicting transmission loss in shallow water, both of which provide depth-averaged estimates for range-independent ocean environments. One model (Rogers, 1981) was derived from theoretical (physics-based) considerations. The second model (Marsh and Schulkin, 1962b Schulkin and Mercer, 1985),...

## Mathematical models Part

Mathematical models of underwater acoustic propagation include both numerical models and empirical models. Chapter 4 addressed the theoretical development of numerical models and summarized their availability. This chapter addresses the development of empirical models applicable to special propagation paths such as surface ducts, shallow water and Arctic half-channels. Where appropriate, comparisons are made with predictions generated by numerical models. Data support requirements for...

## Propagation II mathematical models Part Two152

5.2.3 Oceanographic mixed-layer models 155 5.3 Shallow-water duct models 158 5.3.1 Shallow-water propagation characteristics 158 5.3.2 Optimum frequency of propagation 159 5.4.1 Arctic environmental models 172 5.4.2 Arctic propagation models 172 5.5 Data support requirements 176 5.5.1 Sound-speed profile synthesis 177 5.5.2 Earth curvature corrections 179 5.6 Special applications and inverse techniques 180 5.6.3 Matched field processing 183 5.6.4 Transmutation approaches 185 5.6.6...

## Model evaluation

Model evaluation is defined as the systematic gathering and promulgation of information about models in order to determine model limitations and domains of applicability. Model evaluation should be viewed as a process rather than a specific result. The intent of this chapter is not to furnish a compendium of evaluation results but rather to describe the evaluation process itself. Such a description can provide useful insights into the benefits and shortcomings of model evaluation. The...

## A I

Figure 4.9 A typical ray path with beam displacement included (Tindle and Bold, 1981). A _ 2khP1P2 (Y2 + Y22) Y1Y2 (p2Y22 + P KI2) where kh is the horizontal wavenumber in the water layer A typical ray path for this simple model is presented in Figure 4.9. The source and receiver depths are zo and z, respectively. A ray leaving the source at an angle 0 relative to the horizontal travels in a straight (unrefracted) path in the water layer. There is no beam displacement at the sea surface and the...

## Observations and physical models

Reverberation is defined as that portion of the sound received at a hydrophone that is scattered by the ocean boundaries or by volumetric inhomogeneities. Accordingly, reverberation-producing scatterers in the sea can be grouped into three classes sea surface, sea floor and ocean volume. Surface and bottom reverberation both involve a 2D distribution of scatterers and therefore can be considered jointly as boundary reverberation. Volume reverberation is produced by the marine life and inanimate...

## Mathematical models

Mathematical models of reverberation generate predictions of boundary and volumetric reverberation using the physical models of boundary and volumetric scattering strengths developed in Chapter 8. The development of reverberation models has proved to be formidable for two reasons e.g. Moritz, 1982 Goddard, 1993 . First, there are theoretical difficulties in solving complex boundary value problems for which analytical tools are poorly developed. Second, there are practical difficulties in...

## Soundspeed distribution

Typical North Atlantic winter and summer profiles of sound speed versus depth are shown in Figure 2.6. These profiles represent a region of the North Atlantic Ocean located near 23 N and 70 W Naval Oceanographic Office, 1972 . Temperature-salinity T-S diagrams for winter and summer seasons, based on actual measurements, are also presented to show their relationships with the sound-speed profiles. Since the T-S diagrams indicate the ocean depths corresponding to the measured T-S pairs, the...

## Navoceano

Climatic data files NCDC http lwf.ncdc.noaa. gov oa ncdc.html NGDC Marine Geology and Geophysics data files NODC data files http www.nodc. noaa.gov Table 10.5 Databases from the US Navy TOWAN. Abbreviations and acronyms are defined in Appendix A High-frequency bottom loss HFBL Low-frequency bottom loss LFBL Generalized digital environmental model GDEM Historical wind speed HWS Digital bathym trie data base - variable resolution DBDB-V Volume scattering strength VSS Shipping Noise - High...

## Appendix B Glossary of terms

Absorption - loss of acoustic energy due to conversion to heat. Accreditation - the official certification that a model or simulation is acceptable for a specific purpose. Acoustic daylight - imaging of underwater objects using the ambient noise field. Acoustic impedance - characteristic acoustic impedance is quantitatively equal to the product of the density and sound speed of the medium. Acoustic tomography - inverse technique that uses acoustic signals to sample the interior of a water body....

## Q 12 15

Figure 3.21 Fluctuations in the depth of the mixed layer caused by the passage of internal waves. Water temperature is measured in F. The MLD is defined by the 58 F isotherm. LaFond, 1962 The Sea, Vol. 1, 731-51 reprinted by permission of John Wiley amp Sons, Inc., all rights reserved. extensive data set collected during the AMOS program Marsh and Schulkin, 1955 has been used to characterize TL in the surface duct in the frequency range 2-8 kHz. Graphical results derived from Condron etal. 1955...

## Sonar performance models

The ultimate purpose of sonar performance modeling is two-fold. First, advanced sonar concepts can be optimally designed to exploit the ocean environment of interest. Second, existing sonars can be optimized for operation in any given ocean environment. In the case of naval sonars, performance prediction products can be tailored to individual sonar systems by providing the sonar operators with on-scene equipment mode selection guidance. When combined with current tactical doctrine, this...

## Henry Weinberg Cass Grab

Figure 10.12 Sample acoustic modeling data flow concept showing model operating system application functions for the active sonar equation Locklin and Etter, 1988 . Figure 10.12 Sample acoustic modeling data flow concept showing model operating system application functions for the active sonar equation Locklin and Etter, 1988 . describes the nature of the signal reflected from the target and considers the effects of target strength TS , as specified in the active sonar equation. Furthermore,...

## R0

Where Ro is the mean radius of Earth 6,370.949 km , c- the input sound speed at depth z- and c the corrected sound speed at corrected depth Zi. The effect of curvature is more than just a matter of chords versus arcs of great circles. Rather, the important feature is that the contours of constant sound speed as represented on a range-depth plane are actually concentric spheres instead of flat, parallel planes. The differences in ray angles as calculated by Snell's law produce effects of...

## Underwater Acoustic Transmission Umpe

CORE 75 RDFFP 76 RD-OASES 77 RDOASP 78 RDOAST 79 Use single environmental specification AMPE CMPE 81 CCUB SPLN CNP1 82 Corrected PE 83 DREP 84 FDHB3D 85 FEPE 86 FEPE-CM 87 FEPES 88 FOR3D 89 HAPE 90 HYPER 91 IFD Wide Angle 92 IMP3D 93 LOGPE 94 MaChl 95 MOREPE 96 OS2IFD 97 1 CAPARAY simulates the effects of layering in the ocean bottom on the propagation of a broadband signal. The ocean bottom is characterized by a geoacoustic profile that includes compressional and shear velocities, density and...

## Simulation313

12.3 Simulation infrastructure 316 12.4 High-level architecture 317 12.6.2 Simulation-based acquisition 320 Appendix A Abbreviations and acronyms 328 Appendix B Glossary of terms 342 Broadly defined, modeling is a method for organizing knowledge accumulated through observation or deduced from underlying principles while simulation refers to a method for implementing a model over time. The field of underwater acoustic modeling and simulation translates our physical understanding of sound in the...

## Physical and chemical properties

Temperature is basic to any physical description of the oceans. It is the easiest and therefore the most common type of oceanographic measurement made. The exchange of heat between the ocean and the atmosphere depends strongly on temperature. The density field and resulting stratification of the ocean depend largely on temperature. The speed of sound in the upper layers of the ocean is most strongly dependent on temperature. Temperate further influences the kinds and rates of chemical reactions...

## Negative Sound Speed Gradient

B Depth of SUW salinity maximum - winter b Depth of SUW salinity maximum - summer C Depth of 18 Water core-winter c Depth of 18 Water' core - summer D Depth of MIW salinity maximum - winter d Depth of MIW salinity maximum - summer SUW Subtropical underwater MIW Mediterranean intermediate water Figure 2.6 Sound speed profiles winter and summer and T-S comparisons for the North Atlantic Ocean near 23 N, 70 W Naval Oceanographic Office, 1972 . Figure 2.7 Schematic relationship between profiles in...

## Calculation and measurements

Many empirical relationships have been developed over the years for calculating sound speed using values of water temperature, salinity and pressure or depth . Frequently used formulas include those of Wilson 1960 , Leroy 1969 , Frye and Pugh 1971 , Del Grosso 1974 , Medwin 1975 , Chen and Millero 1977 , Lovett 1978 , Coppens 1981 and Mackenzie 1981 . As summarized in Table 2.1, each formula has its own ranges of temperature, salinity and pressure or depth . Collectively, these ranges are...

## London And New York

Simultaneously published in the USA and Canada by Spon Press 29 West 35th Street, New York, NY 10001 This edition published in the Taylor amp Francis e-Library, 2003. Spon Press is an imprint of the Taylor amp Francis Group 2003 Paul C. Etter All rights reserved. No part of this book may be reprinted or reproduced or utilised in any form or by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying and recording, or in any information storage or...

## Reverberation II mathematical models244

9.2 Theoretical basis for reverberation modeling 244 9.2.2 Advanced developments 247 9.3.1 Volume-reverberation theory 248 9.3.2 Boundary-reverberation theory 250 9.4 The REVMOD model - a specific example 251 9.5.1 Computational considerations 255 9.5.2 The bistatic acoustic model - a specific example 257 9.6 Point-scattering models 259 9.6.1 Computational considerations 259 9.6.2 The under-ice reverberation simulation model - a specific example 260 9.7 Numerical model summaries 261

## Sonar performance models264

10.3 The NISSM model - a specific example 270 10.3.5 Signal-to-noise ratio 276 10.3.6 Probability of detection 277 10.4 Model operating systems 281 10.4.2 Sonar modeling functions 283 10.4.4 The generic sonar model - a specific example 286 10.4.5 The comprehensive acoustic system simulation - a specific example 287 10.5 Data sources and availability 288 10.6 Numerical model summaries 292