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REPORT DOCUMENTATION PAGE 



READ INSTRUCTIONS 

 BEFORE COMPLETING FORM 



1. REPORT NUMBER 



NOSC Technical Report 763 (TR 763) 



2. GOVT ACCESSION NO. 



3. RECIPIENT'S CATALOG NUMBER 



4. TITLE (and Sublllle) 



EVALUATION OF SURFACE DUCTS IN SHALLOW WATER 



5. TYPE OF REPORT ft PERIOD COVERED 

 1980-1981 



6. PERFORMING ORG. REPORT NUMBER 



7. AUTHORCs; 



J. A. Whitney 

 D. F. Gordon 

 J. G. Colborn 



8. CONTRACT OR GRANT NUMBERfs; 



9. PERFORMING ORGANIZATION NAME AND ADDRESS 



Naval Ocean Systems Center 

 San Diego, C A 92152 



63795N-R0120-SH 

 R0120-SH (NOSC724-ST11) 



II. CONTROLLING OFFICE NAME AND ADDRESS 



Naval Ocean Research & Development Activity 

 Bay St Louis, MS 39529 



12. REPORT DATE 



29 March 1982 



13. NUMBER OF PAGES 

 154 



14. MONITORING AGENCY NAME ft ADDRESSf// d///eranr Irom Controlling Otllca) 



15. SECURITY CLASS, (ol thia report) 



Unclassifled 



16. DISTRIBUTION STATEMENT (ol this Report) 



Approved for public release; distribution unlimited 



Woods Hole Oceanographic Institution 



17. DISTRIBUTION STATEMENT (ol the abstract entered In Block 20, II dlllerent Irom Report) 



18. SUPPLEMENTARY NOTES 



19. KEY WORDS rConf/nue on reve 



Positive gradient profile 

 Non-positive gradient profde 



osary and Identity by block number) 



20. ABSTRACT (Continue on reverse side H necessary and Identity by block number) 



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 



DD ,: 



FORM 

 AN 73 



1473 



EDITION OF 1 NOV 65 IS OBSOLETE 



S/N 0102- LP- 014- 6601 



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