62 



Observations and Measurements of Ocean Waves 



predominant : in the lower latitudes (zone of the trade winds and doldrums) 

 more than 50% of all observations fall between the scale points and 3. 

 Even in the middle southern latitudes (the west wind zone), about 50% of 

 the observations fall in the categories to 4. In the northern and north- 

 western part of the Indian Ocean it is necessary to make a division for the 

 two main seasons, because of the change of the monsoon (from May to 

 September : the south-west monsoon and from October to April : the north- 

 east monsoon). These tropical seas are in the south-west monsoon period 

 about just as agitated as the annual average of the west wind zones. However, 

 in the season of the north-east monsoon 84% of all observations indicate 

 a slight sea; state of the sea 4 or 5 are exceptional. 



The presentation by Schumacher should be considered a first trial. It has, 

 however, been very useful and it seems that a more detailed statistical 

 presentation of many more observations on the state of the sea will give 

 excellent results. 



Schumacher has also tried to relate the scale of the state of the sea to 

 absolute values derived from wave measurements. Such comparisons were 

 also attempted in former times, but they were rather inaccurate as they were 

 based only on estimates of wave motion. 



The International Maritime Commission organized from 14th to 19th 

 November, 1938, an international week to observe swell in the Atlantic Ocean, 

 in which 210 ships and 70 coastal stations participated. The extensive ob- 



Table 10. State of the sea motion and dimensions of the swell 



(for winds 0-5 Beaufort) 



servations were subjected to a thorough analysis by Keyser (1946). Table 10 

 gives a compilation of the statistical comparison of actual sea-scale values 



