Table 5.— U.S. institutions, investigators, and projects in POLYMODE (Cont.) 



Institutions 



Investigators 



Yale University 



D.C.Webb 

 F. Webster 

 R. Hall 



Projects 



Float Project 



Newsletter 



Nonlinear Effects on the Scattering of Quasi- 



Geostrophic Waves 



Figure 16 shows an example of the position track and 

 temperature-pressure telemetry for a POLYMODE float. 



To free SOFAR floats from the constraint of being in the 

 listening range of shore stations, four self-contained, moored, 

 float-tracking stations, referred to as autonomous listening sta- 

 tions (ALS), are being built and tested as part of POLYMODE. 

 The POLYMODE float project is designed to rely on shore- 

 based receiving stations and will provide a controlled test of 

 ALS performance. 



To provide an acceptable deployment duration (6-12 months), 

 ALS must preprocess the acoustic signals it receives and only 

 record those that appear to be from floats. The processing 

 algorithm currently being used reduces the data by a factor of 

 62.5 and gives a duration of 2 frequency channel years, or 

 about 100 float years. The battery life is at least 18 months. 



The prototype ALS was deployed for 8 days in January 1977 

 on the slope of San Salvador Island near the depth of the sound 

 channel axis. This test produced a short but encouraging record 

 of detected float signals. The instrument was then deployed off 

 Plantagenet Bank south of Bermuda from April to October 

 1977 and provided a data base of more than 9,000 signals for 

 performance analysis. Results indicate that out to a range of 

 1,300 km there is negligible reduction in the ALS performance 

 owing to data compression procedures. 



Soviet Measurements 



The U.S.S.R. POLYMODE field program began in June 

 1977 and will extend to August 1978. The strategy of the 

 Soviet program is to investigate the kinematics and dynamics 

 of the mesoscale eddies by repetitive synoptic surveys in a block 

 of the ocean encompassing several eddies. Simultaneously, a 

 moored current meter array will determine eddy characteristics 

 (scales and energy levels) within the region, and, if records are 

 sufficiently long, eddy statistics. Nineteen surface moorings have 

 been deployed, and these will be instrumented at five levels to 

 a maximum subsurface depth of 1,500 m. These moorings are 

 deployed in a multiantenna array (fig. 17) that is centered on 

 29°N, 70°W. The array consists of five combined nonsymetric 

 cross-shaped clusters with elements arranged in a pattern similar 

 to that planned for the clusters of U.S. Array III. Current 

 meters and temperature recorders were placed at 100-, 400-, 

 700-, 1,400-, and (on some moorings) 4,000-m levels. Tempera- 

 ture is measured at 100 and 700 m. 



The Soviets are carrying out 10 to 12 synoptic density sur- 

 veys. XBTs, supplied by the United States, will be used along 

 with Soviet CTDs. Each survey will require about 20 days, and 

 will cover an area about 500 km in diameter. Spacing between 

 XBT soundings will be about 30 km. All density data are re- 



ported by radio using the Integrated Global Ocean Station Sys- 

 tem (IGOSS). NOAA's National Weather Service constructs 

 charts of the data and retransmits these charts to Soviet and 

 American ships via facsimile. (See fig. 18.) 



Soviet measurements are closely integrated with United States 

 efforts as part of the Local Dynamics Experiment. A United 

 States current meter array (10 moorings, 31 current meters. 



Loading SOFAR floats for sea. 



25 



