SURVEYING THE OCEANS (OCEANOGRAPHIC) 47 



Portion of wave record from laser sea and swell recorder. 



A sonic echoing device mounted on the bow of a ship has also 

 been used to record waves continuously. This system automatically 

 compensates for the ship motions and can measure waves from 0.5 

 to 40 feet in height. 



At present the bulk of wave observations used in synoptic 

 applications are visual in nature. These are being replaced by 

 the more reliable, instrumented measurements which will permit 

 us to predict wave conditions in the much more sophisticated 

 format required for military operations. 



PHYSICAL AND CHEMICAL PROPERTIES 



In keeping with its predominant influence on sonar behavior, 

 water temperature is the ocean property most widely measured 

 and exploited by the Fleet. More than 5,000 bathythermograph 

 (BT) lowerings are made every month, primarily by Navy ships 

 supplemented by Coast Guard and other ships. Each lowering, 

 usually to depths between 400 and 900 feet, produces a temper- 

 ature profile whose values are reported by radio. These data are 

 the prime input used by the Oceanographic Office and the Naval 

 Weather Service in deriving daily maps of near-surface sonar 

 propagation conditions. 



By stopping to lower precise thermometers or electrically 

 recording thermistors, Oceanographic Office survey ships observe 

 temperatures to greater depths than are obtainable by the BT. 



