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CHAPTER IX. WAVES 



9000. GENERAL 



9010. The wave group of the weather message, as entered on Form 

 615-5, consists of the direction of movement, period, and height of the 

 waves on the surface of the sea. When more than one wave system is 

 present (sea and swell), the direction, period, and height of the waves in 

 each system will be observed and recorded as if they existed alone. 



9020. The wave record section (columns 34-47) of W. B. Form 615-5 

 consists of two parts, one section for entry of sea and swell data similar 

 to a "rough log" and one section for "smooth" data. The first section 

 (columns 34-39) is grey and is used for later transcription to punched cards; 

 the second wave section is white and is used for radio transmission when 

 authorized. Both the grey and white sections refer to the same waves, 

 that is, columns 34-36 and 41-43 are for the same observation of sea 

 waves, columns 37-39 and 45-47 for the swell waves. Additional wave 

 data may be recorded under column 48, "Remarks." 



9030. Waves in the same system usually occur in a sequence of a few, 

 large, well- formed waves followed by an interval in which only small and 

 poorly formed waves appear, then another series of large, well- formed 

 waves, etc. (see Fig. 11). To obtain uniform waves data from all ships, 

 observers will record only the larger, well-formed waves, and omit en- 

 tirely the low and poorly formed waves. 



I I I I I I I 



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Six Second Intervals 



Figure 11. -- Section of a trace from an automatic wave recorder il- 

 lustrating the up-and-down movement of a small object floating on the 

 surface of the sea. In accordance with 319020, the height and period of 

 only the well-defined waves (A) of each group will be determined. 



