Evaluation of Surface Ducts in Shallow Water.
Nine shallow water areas of strategic interest were selected for a preliminary study of surface ducts in shallow water. The objective was to determine the relative percentage of surface ducts versus downward refractive conditions. Sound speed profiles from National Oceanographic Data Center (NODC) N...
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ftdtic:ADA116041 2023-05-15T15:43:54+02:00 Evaluation of Surface Ducts in Shallow Water. Whitney,J A Gordon,D F Colborn,J G NAVAL OCEAN SYSTEMS CENTER SAN DIEGO CA 1982-03-29 text/html http://www.dtic.mil/docs/citations/ADA116041 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA116041 en eng http://www.dtic.mil/docs/citations/ADA116041 APPROVED FOR PUBLIC RELEASE DTIC AND NTIS Physical and Dynamic Oceanography Acoustics *Sound transmission Ocean surface Underwater sound Shallow water Oceans Refraction Gradients Ducts Acoustic velocity Profiles Transmission loss North Sea Juan de Fuca Strait Singapore North Atlantic Ocean Korean Strait Mediterranean Sea Bering Sea Brazil Bass Strait Sicily Strait Surface ducts PE63795N WU724ST11 Text 1982 ftdtic 2016-02-19T08:07:51Z Nine shallow water areas of strategic interest were selected for a preliminary study of surface ducts in shallow water. The objective was to determine the relative percentage of surface ducts versus downward refractive conditions. Sound speed profiles from National Oceanographic Data Center (NODC) Nansen cast files and XBT profiles were classified by computer as either positive or negative (non-positive) gradient profiles. Ninety percent of the fall-winter and 31 percent of the spring-summer profiles were of positive gradient (or surface duct)type. Percentages are given for each of the nine cases. Representative profiles and sea floor data from six of the sites were used to compute propagation loss. These losses, computed by normal mode theory, were used to determine the frequency of optimum propagation at these sites for positive and non-positive gradient profiles. Positive gradient (winter) profiles generally resulted in at least 10 dB less loss at 50 km range than did non-positive gradient profiles. Optimum propagation for positive gradient surface ducts varied from 200 to 1000 Hz. The reflectivity of the bottom models varied greatly. Where propagation was relatively good by bottom reflected paths, optimum frequencies were around 500 Hz. The greatest differences between propagation losses calculated for the positive and non-positive profile cases are seen where such reflectivity is poor. (Author) Text Bering Sea North Atlantic Defense Technical Information Center: DTIC Technical Reports database Bering Sea |
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Open Polar |
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Defense Technical Information Center: DTIC Technical Reports database |
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ftdtic |
language |
English |
topic |
Physical and Dynamic Oceanography Acoustics *Sound transmission Ocean surface Underwater sound Shallow water Oceans Refraction Gradients Ducts Acoustic velocity Profiles Transmission loss North Sea Juan de Fuca Strait Singapore North Atlantic Ocean Korean Strait Mediterranean Sea Bering Sea Brazil Bass Strait Sicily Strait Surface ducts PE63795N WU724ST11 |
spellingShingle |
Physical and Dynamic Oceanography Acoustics *Sound transmission Ocean surface Underwater sound Shallow water Oceans Refraction Gradients Ducts Acoustic velocity Profiles Transmission loss North Sea Juan de Fuca Strait Singapore North Atlantic Ocean Korean Strait Mediterranean Sea Bering Sea Brazil Bass Strait Sicily Strait Surface ducts PE63795N WU724ST11 Whitney,J A Gordon,D F Colborn,J G Evaluation of Surface Ducts in Shallow Water. |
topic_facet |
Physical and Dynamic Oceanography Acoustics *Sound transmission Ocean surface Underwater sound Shallow water Oceans Refraction Gradients Ducts Acoustic velocity Profiles Transmission loss North Sea Juan de Fuca Strait Singapore North Atlantic Ocean Korean Strait Mediterranean Sea Bering Sea Brazil Bass Strait Sicily Strait Surface ducts PE63795N WU724ST11 |
description |
Nine shallow water areas of strategic interest were selected for a preliminary study of surface ducts in shallow water. The objective was to determine the relative percentage of surface ducts versus downward refractive conditions. Sound speed profiles from National Oceanographic Data Center (NODC) Nansen cast files and XBT profiles were classified by computer as either positive or negative (non-positive) gradient profiles. Ninety percent of the fall-winter and 31 percent of the spring-summer profiles were of positive gradient (or surface duct)type. Percentages are given for each of the nine cases. Representative profiles and sea floor data from six of the sites were used to compute propagation loss. These losses, computed by normal mode theory, were used to determine the frequency of optimum propagation at these sites for positive and non-positive gradient profiles. Positive gradient (winter) profiles generally resulted in at least 10 dB less loss at 50 km range than did non-positive gradient profiles. Optimum propagation for positive gradient surface ducts varied from 200 to 1000 Hz. The reflectivity of the bottom models varied greatly. Where propagation was relatively good by bottom reflected paths, optimum frequencies were around 500 Hz. The greatest differences between propagation losses calculated for the positive and non-positive profile cases are seen where such reflectivity is poor. (Author) |
author2 |
NAVAL OCEAN SYSTEMS CENTER SAN DIEGO CA |
format |
Text |
author |
Whitney,J A Gordon,D F Colborn,J G |
author_facet |
Whitney,J A Gordon,D F Colborn,J G |
author_sort |
Whitney,J A |
title |
Evaluation of Surface Ducts in Shallow Water. |
title_short |
Evaluation of Surface Ducts in Shallow Water. |
title_full |
Evaluation of Surface Ducts in Shallow Water. |
title_fullStr |
Evaluation of Surface Ducts in Shallow Water. |
title_full_unstemmed |
Evaluation of Surface Ducts in Shallow Water. |
title_sort |
evaluation of surface ducts in shallow water. |
publishDate |
1982 |
url |
http://www.dtic.mil/docs/citations/ADA116041 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA116041 |
geographic |
Bering Sea |
geographic_facet |
Bering Sea |
genre |
Bering Sea North Atlantic |
genre_facet |
Bering Sea North Atlantic |
op_source |
DTIC AND NTIS |
op_relation |
http://www.dtic.mil/docs/citations/ADA116041 |
op_rights |
APPROVED FOR PUBLIC RELEASE |
_version_ |
1766378115666280448 |