concentration basin* with respect to the western basin. The exchanges of water through 

 the Straits of Sicily are similar to those between the Mediterranean Sea and the Atlantic 

 Ocean. The currents are less complex due to the broad extent of the Straits of Sicily 

 relative to the Strait of Gibraltar and to the greater difference in the mean salinities of the 

 Mediterranean and the Atlantic water. The Korea Strait site is on the broad continental 

 shelf off China and under the influence of the Kuroshio current from the south and the 

 intrusion of cold water from the Sea of Japan to the northeast. 



The shallow Bering Sea is a high latitude site within a large, flat area of shallow 

 water between 50 and 1 50 m and one in which propagation loss tests have been reported 

 (References 4, 5). The site in the Bass Strait was added to extend the coverage into 

 southern latitudes. The site near the mouth of the Amazon River is on the continental 

 shelf off the coast of Brazil under the influence of the open sea and the outflow of the 

 Amazon. This site is similar in those respects to the Juan de Fuca site but differs in 

 latitude and depths of water. 



These sites are located on a world map in Figure 2. 1 (the actual place is called out 

 in alphabetical order as hsted in Table 2.1) and on surrounding area charts in Figure 2.2. 



2.2 Sound Speed Profiles 



The purpose of the sound speed profile selection process as described below was 

 two-fold. The first was to provide reliable estimates of the occurrence of surface ducts in 

 shallow water areas for different times (seasons) of the year. The second was to determine 

 characteristic profiles to represent an area for use in normal mode calculations of propaga- 

 tion loss. 



2.2.1 Assessment 



The primary source of sound speed data for this study was the National Oceano- 

 graphic Data Center (NODC) Nansen cast archival data file. This file provides profiles of 

 ocean temperature, saHnity and computed sound speed at standard depths of 0, 10, 20, 30, 

 50, 75, 100, 150 and 200 meters (Wilson's October sound speed equation (Reference 6) is 

 used). To supplement the number of available profiles, the NODC archival XBT data file 

 was searched for suitable temperature profiles. These profiles were then converted to sound 

 speed profiles using the annual mean salinity profile from the Nansen cast data at that site 

 and then were interpolated for sound speed at standard depths. The XBT data contributed 

 significantly to the sample size in several cases, especially at the site East of Singapore. The 

 XBT data were not used at other sites where ample Nansen cast stations were available. 

 XBT data were used to increase the sample size in four different instances. 



♦The amount of evaporated water exceeds that gained by the precipitation and river discharges. The entire 

 Mediterranean is a typical example of a concentration basin. 



4. LORAD Tests in the Shallow Bering Sea, J. A. Whitney, Naval Electronics Laboratory Report 1 160, 

 February 1963. 



5. Long-Range Acoustic Propagation in the Shallow Bering Sea, K. V. Mackenzie, Naval Undersea 

 Center TP 293, June 1972. 



6. Equations for the Sound Speed in Sea Water, W. D. Wilson, J. Acoust. Soc. Am., Vol 32, 1960, p 1357 

 (L). 



